GeometryScript

69 tools. Back to the index.

append_mesh_primitive

Additive.

Append a Box, Sphere, Cylinder or Cone to the live dynamic mesh of a DynamicMeshActor in the editor world, keeping the geometry already there: size is the box edge or the diameter and height of the round shapes, centred at location in mesh-local space. Each call adds another copy, inside an editor transaction; nothing is saved to an asset. An unknown actor or primitive is an error; appended is true when the triangle count grew. To merge another actor's mesh use append_mesh_to_dynamic_mesh; to persist the result, copy_dynamic_mesh_to_static_mesh.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
primitive	string	no	Box, Sphere, Cylinder, or Cone, default Box
size	number	no	Dominant dimension in cm, default 100
location	array	no	Optional local [x, y, z] offset for the primitive
dimensions	number	no	Fallback alias for size when size is omitted (cm)
material_id	number	no	Optional MaterialID stamped on the appended triangles (default 0). Non-zero enables the mesh MaterialID attribute first, so a later copy_dynamic_mesh_to_static_mesh (bUseSectionMaterials=true) emits this piece as its own section/material slot. This is how one dynamic mesh becomes a multi-slot static mesh.

Returns: { actor_name: string, primitive: string, size: number, material_id: int, triangle_count: int, triangles_added: int, vertex_count: int, appended: bool }

append_mesh_to_dynamic_mesh

Additive.

Merge another UDynamicMesh into the live dynamic mesh of a DynamicMeshActor via UGeometryScriptLibrary_MeshBasicEditFunctions::AppendMesh.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor (the receiver)
source_actor_name	string	yes	Label or name of the DynamicMeshActor whose dynamic mesh will be merged in
append_transform	array	no	Optional [x,y,z] world-space transform applied to the source mesh before merging (default identity)

Returns: { actor_name, source_actor_name, triangles_before, triangles_after, triangles_added, vertex_count_after, appended: true }

apply_adaptive_remesh

Destructive.

Adaptive-remesh a DynamicMeshActor's dynamic mesh using a target edge length and optional weight map

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
max_edge_length	number	yes	Target edge length for adaptive remesh (sets TargetType=TargetEdgeLength + TargetEdgeLength). Required.
min_edge_length	number	no	Soft floor for adaptive edge length (default 1.0). NOTE: FGeometryScriptAdaptiveRemeshOptions has no explicit min field — this is echoed back in the result for traceability but is NOT consulted by the engine call.
relative_density	number	no	Density adjustment in [-2.0, 2.0] passed to FGeometryScriptAdaptiveRemeshOptions::RelativeDensity (default 0.0).
weight_map_name	string	no	Optional name of an existing vertex weight map (resolved via UGeometryScriptLibrary_MeshQueryFunctions::GetWeightMapHandle). If omitted or the mesh does not have such a layer, the engine runs adaptive remesh without a weight map (its default invalid handle).

Returns: { actor_name: string, min_edge_length: number, max_edge_length: number, relative_density: number, weight_map_name: string, weight_map_resolved: bool, target_type: string, triangle_count: int, triangle_count_before: int, vertex_count: int, remeshed: bool }

apply_mesh_boolean

Destructive.

Apply a CSG boolean (Subtract by default, Union or Intersect) between the live dynamic mesh of a DynamicMeshActor in the editor world and a temporary primitive tool: other_primitive (Sphere by default) of size cm, offset by location in mesh-local space. The target is changed in place inside an editor transaction, nothing is saved, and each call cuts or merges again. An unknown actor, operation or primitive is an error. When the engine refuses the result (an empty one, such as subtracting from an empty mesh) the mesh is left unchanged, boolean_applied is false and the call fails. To use another actor's mesh as the tool call apply_mesh_boolean_actor_to_actor.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
operation	string	no	Union, Subtract, or Intersect, default Subtract
other_primitive	string	no	Tool primitive shape, default Sphere
size	number	no	Tool primitive size in cm, default 100
location	array	no	Optional tool [x, y, z] offset
dimensions	number	no	Fallback alias for size when size is omitted (cm)

Returns: { actor_name: string, operation: string, other_primitive: string, triangle_count: int, triangle_count_before: int, vertex_count: int, boolean_applied: bool }

apply_mesh_boolean_actor_to_actor

Destructive.

Apply a CSG boolean using a second DynamicMeshActor as the cutting tool. Unlike apply_mesh_boolean (which builds a transient primitive tool), the tool geometry is the live dynamic mesh of source_actor_name. The target mesh is mutated in place; the source mesh is left untouched. NOT idempotent: re-running keeps cutting/merging the same tool against the already-modified target. When the engine refuses the result (an empty one) the target is left unchanged, boolean_applied is false and the call fails.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor (the receiver, mutated in place)
source_actor_name	string	yes	Label or name of the DynamicMeshActor whose live dynamic mesh is used as the boolean tool
operation	string	no	Union, Subtract, or Intersect, default Subtract
use_world_transforms	boolean	no	Optional bool, default true. When true the tool is positioned by the relative world transform (source relative to target) so the boolean respects the actors' placement; when false the tool is applied at identity (co-located).
fill_holes	boolean	no	Optional bool override for FGeometryScriptMeshBooleanOptions.bFillHoles (default true)
simplify_output	boolean	no	Optional bool override for FGeometryScriptMeshBooleanOptions.bSimplifyOutput (default true)

Returns: { actor_name: string, source_actor_name: string, operation: string, triangle_count: int, triangle_count_before: int, vertex_count: int, boolean_applied: bool }

apply_mesh_morphology

Destructive.

Apply an SDF-based morphology op (dilate/contract/close/open) to a DynamicMeshActor's dynamic mesh. Replaces the mesh with an SDF-based offset mesh approximation.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
operation	string	yes	Required. One of: dilate, contract, close, open.
distance	number	yes	Required positive float. Offset distance in cm (SDF-based).

Returns: { actor_name, operation, distance, triangle_count, triangle_count_before, vertex_count, morphed }

apply_mesh_solidify

Destructive.

Voxel-wrap a DynamicMeshActor's dynamic mesh (replaces the mesh with a voxelised-and-meshed approximation).

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
winding_threshold	number	no	Optional [0..1], default 0.5. Space with generalised winding number above this is considered inside.
extend_bounds	number	no	Optional positive float, default 1.0. Bounds extension applied to the default input-mesh-based bounds.
surface_search_steps	number	no	Optional int >= 1, default 3. Marching-cubes vertex search steps.
thicken_shells	boolean	no	Optional bool, default false. Thicken open shells into closed solids (expensive on large meshes).
shell_thickness	number	no	Optional positive float, default 1.0. Offset distance for shell thickening.

Returns: { actor_name, triangle_count, triangle_count_before, vertex_count, solidified }

apply_uniform_remesh

Destructive.

Remesh the live dynamic mesh of a DynamicMeshActor in the editor world into evenly sized triangles, aiming at target_edge_length (cm) or target_tri_count: exactly one is required, else an error. The mesh changes in place inside an editor transaction and the actor's package is marked dirty, not saved. smoothing_type picks uniform, UV-preserving or mixed smoothing; an unknown value is an error. The reply echoes the settings the engine was given. remeshed is true when the triangle or vertex count changed. For variable density use apply_adaptive_remesh; to only reduce triangles, simplify_mesh.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
target_edge_length	number	no	Target uniform edge length in mesh units (sets TargetType=TargetEdgeLength). Mutually exclusive with target_tri_count; at least one is required.
target_tri_count	number	no	Approximate target triangle count (sets TargetType=TriangleCount). Mutually exclusive with target_edge_length.
preserve_sharp_edges	boolean	no	Approximate 'preserve sharp edges' by enabling bPreventNormalFlips on the shared RemeshOptions (default true; UE's FGeometryScriptUniformRemeshOptions has no explicit preserve-sharp flag, so the closest equivalent is the shared RemeshOptions.bPreventNormalFlips).
smoothing_type	string	no	One of 'uniform' | 'uv_preserving' | 'mixed' (default 'mixed'); maps to EGeometryScriptRemeshSmoothingType on the shared RemeshOptions.
auto_compact	boolean	no	Auto-compact the index space after remesh on the shared RemeshOptions (default true).

Returns: { actor_name: string, target_edge_length: number, target_tri_count: int, preserve_sharp_edges: bool, smoothing_type: string, auto_compact: bool, target_type: string, triangle_count: int, triangle_count_before: int, vertex_count: int, remeshed: bool }

auto_generate_mesh_uvs

Destructive.

Compute a real UV UNWRAP for the whole mesh via UGeometryScriptLibrary_MeshUVFunctions::AutoGeneratePatchBuilderMeshUVs or AutoGenerateXAtlasMeshUVs. This is what sits behind the editor's "Auto UV" button. Use it when a projection is not enough (organic or mixed-orientation geometry); for plank-and-post shapes set_mesh_uvs_from_projection with box is usually cleaner and far cheaper. Both methods PACK the result into standard UV space by default, so island layout is handled too. SLOW on dense meshes: this is a solver, not a projection. A UV channel the mesh does not have, or an empty mesh, is an error; applied is false, and the call fails, when the solver reports an error (xatlas needs a compact mesh: run compact_mesh first).

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
method	string	no	'patch_builder' (default, the editor's Auto UV) or 'xatlas'.
uv_channel	number	no	UV channel to write (default 0).
initial_patch_count	number	no	patch_builder: how many patches to seed (default 100). More patches = less distortion, more seams.
min_patch_size	number	no	patch_builder: minimum triangles per patch (default 2).
merging_threshold	number	no	patch_builder: patch merging metric threshold (default 1.5). Higher merges more aggressively, giving fewer islands.
max_angle_deg	number	no	patch_builder: max angle in degrees between merged patches (default 45).
respect_polygroups	boolean	no	patch_builder: seed patches from the existing polygroups instead of curvature (default false). Useful right after append_mesh_primitive, where each appended face is already its own group.
auto_pack	boolean	no	Pack the resulting islands into standard UV space (default true).
max_iterations	number	no	xatlas: solver iterations (default 2). Higher is slower and slightly tighter.

Returns: { actor_name, method, uv_channel, triangle_count: int, uv_channel_count: int, applied: bool }

build_mesh_bvh

Read-only.

Build a BVH (bounding volume hierarchy) for the live dynamic mesh of a DynamicMeshActor in the editor world with BuildBVHForMesh, and read it back with IsBVHValidForMesh. The plugin keeps no BVH between calls: this one is dropped on return, and the spatial-query tools (find_nearest_point_on_mesh, find_nearest_ray_intersection_with_mesh, is_point_inside_mesh) build their own on every call, so they never need this first. It checks that a BVH can be built for the mesh as it is now: built is true when the engine reported no error and the BVH reads back as valid; the call fails otherwise. The mesh is not changed.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
b_only_if_invalid	boolean	no	Optional bool, default true; it has no effect, since no earlier BVH is kept and every call builds a new one.

Returns: { actor_name, built: bool, b_only_if_invalid: bool, bvh_valid: bool, vertex_count, triangle_count } -- actor_name is the dynamic mesh component's name, not the actor label; b_only_if_invalid echoes the request; the counts are those of the mesh the BVH was built for.

clear_dynamic_mesh

Destructive, idempotent.

Empty a DynamicMeshActor's live UDynamicMesh in place (keep the actor, drop the geometry).

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the DynamicMeshActor to clear (required).

Returns: { actor_name: string, triangle_count_before: int, triangle_count_after: int, vertex_count_before: int, vertex_count_after: int, cleared: bool }

compact_mesh

Destructive.

Compact vertex and triangle ID lists on a DynamicMeshActor's dynamic mesh

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor

Returns: { actor_name: string, triangle_count: int, vertex_count: int, compacted: bool }

copy_dynamic_mesh_to_static_mesh

Destructive, idempotent.

Write the live dynamic mesh of a DynamicMeshActor INTO an EXISTING /Game UStaticMesh asset's LOD via UGeometryScriptLibrary_StaticMeshFunctions::CopyMeshToStaticMesh (7-arg V2, bUseSectionMaterials=true; engine-default options). Editor-only (the engine function is WITH_EDITOR-gated and touches GEditor + FlushRenderingCommands). Idempotent: overwrites the target LOD in place, no duplication. HONEST GATES: the target asset must already exist (create it first, e.g. via create_editable_static_mesh) and must NOT live under /Engine/ (the engine refuses to modify built-in engine assets). A lod_index outside 0 to 7 (a static mesh has at most 8 LODs) is an error checked before anything changes; one past the asset's last LOD adds the LODs in between, which the engine sets up to be reduced from an earlier LOD.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the source DynamicMeshActor.
target_static_mesh_path	string	yes	Content path of an EXISTING /Game UStaticMesh to overwrite.
lod_index	number	no	Optional target LOD index, 0 to 7 (default 0); a negative index or one of 8 or more is refused.
materials	array	no	Optional ordered list of UMaterialInterface content paths, one per MaterialID (index 0 = MaterialID 0). Supplying it flips bReplaceMaterials on, so the target asset gets exactly these material slots. WITHOUT this the asset keeps its existing slots and a multi-MaterialID mesh collapses into whatever slots already existed — this is the parameter that makes per-triangle MaterialIDs visible on the saved asset.
material_slot_names	array	no	Optional slot names matching materials 1:1 (default: the engine names them). Ignored when materials is absent.

Returns: { actor_name, target_static_mesh_path, lod_index, outcome_success: bool, source_triangle_count, material_count: int, replaced_materials: bool, wrote: bool }. NOTE: this marks the target package dirty (transaction) but does NOT save to disk — persistence requires a separate save (e.g. via save_asset).

copy_mesh_uv_channel

Additive.

Copy UV data from one UV channel to another on the same mesh. A dest_channel the mesh does not have yet is added first (the channel count only grows, and channels added in between have no UVs set); a source_channel the mesh does not have, or a dest_channel of 8 or more, is an error checked before anything changes. copied is false, and the call fails, when the engine reports an error; the same channel for both is a no-op that succeeds with copied false and a note. No undo entry, nothing saved.

Parameter	Type	Required	Description
actor_name	string	yes	DynamicMeshActor name (required)
source_channel	number	yes	Source UV channel index (required)
dest_channel	number	yes	Destination UV channel index, 0 to 7 (required, added to the mesh when it does not have it yet)

Returns: { actor_name: string, source_channel: int, dest_channel: int, copied: bool, num_uv_channels_after: int, note?: string } -- actor_name is the dynamic mesh component's name, not the actor label; copied is false when source_channel equals dest_channel, and note says so or that the mesh grew new channels to reach dest_channel.

copy_static_mesh_to_dynamic_mesh

Destructive, idempotent.

Copy the geometry of a UStaticMesh asset INTO the live dynamic mesh of a DynamicMeshActor via UGeometryScriptLibrary_StaticMeshFunctions::CopyMeshFromStaticMesh (engine-default options: build settings applied, tangents on). Destructive replace of the actor's current mesh. Idempotent-ish: re-running re-extracts the same source geometry (result depends only on the source asset + LOD). Reads the MaxAvailable LOD (LODIndex clamped to the asset's available LODs) so it is robust across meshes with fewer LODs.

Parameter	Type	Required	Description
source_static_mesh_path	string	yes	Content path of the source UStaticMesh (e.g. "/Engine/BasicShapes/Cube").
actor_name	string	yes	Label or name of the target DynamicMeshActor whose GetDynamicMesh() receives the geometry.
lod_index	number	no	Optional source LOD index (default 0). LODType is MaxAvailable, so the index is silently clamped to the asset's LOD count.

Returns: { source_static_mesh_path, actor_name, lod_index, outcome_success: bool, triangle_count, vertex_count, copied: bool }

delete_selected_triangles_from_mesh

Destructive.

Delete the listed triangle IDs from a DynamicMeshActor's live dynamic mesh in the editor world; IDs that do not exist are skipped, so compare num_deleted with requested_count. No undo entry; reply actor_name is the component name, not the actor label.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the target DynamicMeshActor in the editor world.
triangle_ids	array	yes	Non-empty array of non-negative integer triangle IDs, e.g. [0, 5, 12]; any negative or non-numeric entry fails the call.

Returns: { actor_name, num_deleted, requested_count, triangle_count, previous_triangle_count }

delete_triangle_from_mesh

Destructive.

Delete one triangle by ID from a DynamicMeshActor's live dynamic mesh in the editor world; a missing ID is not an error, deleted just comes back false. No undo entry; reply actor_name is the component name, not the actor label.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the target DynamicMeshActor in the editor world.
triangle_id	number	yes	Non-negative integer ID of the triangle to delete.

Returns: { actor_name, triangle_id, deleted, triangle_count, previous_triangle_count }

find_nearest_point_on_mesh

Read-only.

Find the nearest point on the live dynamic mesh of a DynamicMeshActor to a 3D query point via UGeometryScriptLibrary_MeshSpatial::FindNearestPointOnMesh. Every call builds a fresh BVH from the mesh as it is now (the plugin keeps none), then queries it, so the answer always reflects the latest mesh edits. found is false when no triangle lies within max_distance, or the mesh is empty. The mesh is not changed.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
query_point	array	no	[x, y, z] query point in the mesh's local space.
max_distance	number	no	Optional float; max search distance (0 = unlimited).
allow_unsafe_modified	boolean	no	Optional; maps to bAllowUnsafeModifiedQueries (default false). It has no effect: the BVH is built fresh on every call, so it always matches the mesh.

Returns: { actor_name, found: bool, valid: bool, triangle_id, position_x/y/z, bary_coords_x/y/z } -- actor_name is the dynamic mesh component's name, not the actor label.

find_nearest_ray_intersection_with_mesh

Read-only.

Cast a ray against the live dynamic mesh of a DynamicMeshActor and return the nearest hit via UGeometryScriptLibrary_MeshSpatial::FindNearestRayIntersectionWithMesh. Every call builds a fresh BVH from the mesh as it is now (the plugin keeps none), so the answer always reflects the latest mesh edits. The engine normalizes ray_direction, so ray_parameter is the distance from ray_origin to the hit. hit is false when nothing is hit within max_distance. The mesh is not changed.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
ray_origin	array	no	[x, y, z] origin point of the ray in mesh-local space.
ray_direction	array	no	[x, y, z] direction of the ray; the engine normalizes it, so its length does not matter.
max_distance	number	no	Optional float; max search distance (0 = unlimited).
allow_unsafe_modified	boolean	no	Optional; maps to bAllowUnsafeModifiedQueries (default false). It has no effect: the BVH is built fresh on every call, so it always matches the mesh.

Returns: { actor_name, hit: bool, ray_parameter, hit_triangle_id, hit_position_x/y/z, hit_bary_coords_x/y/z } -- actor_name is the dynamic mesh component's name, not the actor label; ray_parameter is a distance along the normalized direction.

generate_mesh_uvs

Destructive, idempotent.

Planar-project UVs for the whole live dynamic mesh of a DynamicMeshActor in the editor world into channel uv_channel, overwriting it: the projection runs down mesh-local Z with 1 UV unit per cm, not fitted to 0-1. A missing channel is added first (the channel count only grows, so higher channels such as a lightmap UV1 are kept). uv_channel 8 or more, or an empty mesh, is an error checked before anything changes; uvs_generated is false (the call fails) when the engine reports an error. Idempotent, in an editor transaction, nothing saved. For box, cylinder or region projections use set_mesh_uvs_from_projection; for a real unwrap, auto_generate_mesh_uvs.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
uv_channel	number	no	UV set index to write, 0 to 7, default 0

Returns: { actor_name: string, uv_channel: int, uv_channel_count: int, triangle_count: int, vertex_count: int, uvs_generated: bool }

get_dynamic_mesh_info

Read-only.

Read geometry stats off a DynamicMeshActor's live dynamic mesh

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor

Returns: { actor_name: string, actor_internal_name: string, triangle_count: int, vertex_count: int, is_closed: bool, is_empty: bool }

get_is_dense_mesh

Read-only.

Return true if the mesh's triangle IDs are dense (no gaps after deletions).

Parameter	Type	Required	Description
actor_name	string	yes	DynamicMeshActor name (required)

Returns: { actor_name, is_dense }

get_mesh_bounding_box

Read-only.

Read the local-space axis-aligned bounding box of a static mesh via UGeometryScriptLibrary_MeshQueryFunctions::GetMeshBoundingBox.

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset (e.g. "/Game/Meshes/SM_Cube")
lod_index	number	no	Optional LOD index to query (default 0, MaxAvailable)

Returns: { static_mesh_path, lod_index, min_x, min_y, min_z, max_x, max_y, max_z, extent_x, extent_y, extent_z, center_x, center_y, center_z }

get_mesh_components_detail

Read-only.

Enumerate the connected components (physical pieces) of a DynamicMeshActor's live dynamic mesh via UE::Geometry::FMeshConnectedComponents, reporting for EACH island its triangle count, its local-space bounding box, its triangle_id range and which MaterialIDs it carries. Read-only (unlike the engine's SplitMeshByComponents, which consumes the mesh). This is the map of a mesh in ONE call, and the tool to reach for BEFORE painting anything: get_mesh_material_ids says how many triangles carry each material, and this says what those triangles physically ARE. HONEST GATE: it names nothing — it gives you sizes and positions, and which island is which part is still a human call; what it prevents is deriving that from a triangle-count assumption.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
max_components	number	no	Cap on how many islands to return (default 64). components_truncated says whether the cap cut the list; component_count is always the real total.
include_triangle_ids	boolean	no	Also return each island's full triangle ID list (default false; use the reported id_min/id_max range instead unless the island is non-contiguous).

Returns: { actor_name, component_count: int, components_truncated: bool, components: [ { index, triangle_count, id_min, id_max, id_contiguous: bool, material_ids: [int], bounds: { min_x, min_y, min_z, max_x, max_y, max_z, center_x, center_y, center_z, size_x, size_y, size_z }, triangle_ids: [int] } ] }

get_mesh_connected_components

Read-only.

Count the number of topologically separate connected components (islands) in a static mesh via UGeometryScriptLibrary_MeshQueryFunctions::GetNumConnectedComponents.

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset
lod_index	number	no	Optional LOD index to query (default 0)

Returns: { static_mesh_path, lod_index, connected_components }

get_mesh_has_attribute_set

Read-only.

Return true if the mesh has at least one attribute set registered.

Parameter	Type	Required	Description
actor_name	string	yes	DynamicMeshActor name (required)

Returns: { actor_name, has_attribute_set }

get_mesh_is_closed

Read-only.

Test whether a static mesh has no topological boundary edges (i.e. is a closed manifold) via UGeometryScriptLibrary_MeshQueryFunctions::GetIsClosedMesh.

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset
lod_index	number	no	Optional LOD index to query (default 0)

Returns: { static_mesh_path, lod_index, is_closed }

get_mesh_material_ids

Read-only.

Read the per-triangle MaterialID distribution of a DynamicMeshActor's live dynamic mesh via UGeometryScriptLibrary_MeshMaterialFunctions::GetMaxMaterialID + GetAllTriangleMaterialIDs. Read-only. This is the ORACLE for every MaterialID write: it returns a per-ID triangle histogram, so "did the paint actually land?" is answerable with a read instead of trusting a success flag. IMPORTANT: has_material_ids=false means the mesh has no MaterialID attribute at all, which is exactly the state in which writes are silently dropped by the engine.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.

Returns: { actor_name, has_material_ids: bool, max_material_id: int, triangle_count: int, distinct_material_ids: int, histogram: [ { material_id: int, triangle_count: int } ] }

get_mesh_open_border_loops

Read-only.

Count the number of open border loops (topological "holes") in a static mesh via UGeometryScriptLibrary_MeshQueryFunctions::GetNumOpenBorderLoops.

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset
lod_index	number	no	Optional LOD index to query (default 0)

Returns: { static_mesh_path, lod_index, open_border_loops, ambiguous_topology }

get_mesh_selection_bounds

Read-only.

Resolve a region into a selection and report its local-space BOUNDING BOX via UGeometryScriptLibrary_MeshSelectionQueryFunctions::GetMeshSelectionBoundingBox. Read-only. Takes exactly the same region parameters as select_mesh_triangles and set_mesh_material_id_in_region, so a region measured here is the same one painted there. This is what turns a bisection answer ("the piece is somewhere in X>0") into actual numbers: centre and size, which is what lets you tell a 150x100x40 slab from a 14x230x75 rail without opening the editor.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
region	string	no	'all' (default) | 'box' | 'sphere' | 'plane' | 'normal_angle' | 'material_id' | 'polygroup' | 'connected_component'.
component_index	integer	no	Island index when region='connected_component'. Get it from get_mesh_components_detail, which reports each piece's size and bounding box.
center	array	no	Local [x,y,z] centre. Used by box/sphere, and as the plane origin.
extent	array	no	Local [x,y,z] HALF-size in cm. Required by region='box'.
radius	number	no	Radius in cm. Required by region='sphere'.
normal	array	no	[x,y,z] direction. Plane normal for region='plane', facing direction for 'normal_angle'. Default [0,0,1].
max_angle_deg	number	no	Max angle from normal in degrees for region='normal_angle' (default 15).
source_material_id	integer	no	MaterialID to select when region='material_id'.
polygroup_id	integer	no	Polygroup to select when region='polygroup'.
polygroup_layer	integer	no	Optional extended polygroup layer index for region='polygroup'.
min_triangle_points	integer	no	How many of a triangle's 3 points must be inside for it to count, 1-3 (default 3).
invert	boolean	no	Invert the spatial selection (default false).

Returns: { actor_name, region, triangles_selected: int, is_empty: bool, bounds: { min_x, min_y, min_z, max_x, max_y, max_z, center_x, center_y, center_z, size_x, size_y, size_z } }

get_mesh_triangle_count

Read-only.

Count the triangles in a static mesh via UGeometryScriptLibrary_MeshQueryFunctions::GetNumTriangleIDs. This is the canonical triangle count after copy-from-asset; GetTriangleCount is also surfaced on UDynamicMesh directly (always == NumTriangleIDs for a freshly copied mesh).

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset
lod_index	number	no	Optional LOD index to query (default 0)

Returns: { static_mesh_path, lod_index, triangle_count, triangle_id_count, has_triangle_id_gaps }

get_mesh_uv_area

Read-only.

Compute the total UV-space area of all triangles in a static mesh's UV channel via UGeometryScriptLibrary_MeshQueryFunctions::GetMeshUVArea. bIsValidUVChannel is false if the mesh has no UVs in that channel.

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset
uv_channel	number	no	UV channel index (default 0)
lod_index	number	no	Optional LOD index to query (default 0)

Returns: { static_mesh_path, lod_index, uv_channel, uv_area, is_valid_uv_channel }

get_mesh_uv_channel_count

Read-only.

Read the number of UV channels in a static mesh via UGeometryScriptLibrary_MeshQueryFunctions::GetNumUVSets.

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset
lod_index	number	no	Optional LOD index to query (default 0)

Returns: { static_mesh_path, lod_index, uv_channel_count }

get_mesh_vertex_count

Read-only.

Count the vertices in a static mesh via UGeometryScriptLibrary_MeshQueryFunctions::GetVertexCount.

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset
lod_index	number	no	Optional LOD index to query (default 0)

Returns: { static_mesh_path, lod_index, vertex_count, vertex_id_count, has_vertex_id_gaps }

get_mesh_volume_area

Read-only.

Read the surface area and signed volume of a static mesh via UGeometryScriptLibrary_MeshQueryFunctions::GetMeshVolumeArea.

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset
lod_index	number	no	Optional LOD index to query (default 0)

Returns: { static_mesh_path, lod_index, surface_area, volume, is_closed }

get_mesh_volume_area_center

Read-only.

Read surface area, signed volume, and center-of-mass of a static mesh via UGeometryScriptLibrary_MeshQueryFunctions::GetMeshVolumeAreaCenter.

Parameter	Type	Required	Description
static_mesh_path	string	yes	Content path to the UStaticMesh asset
lod_index	number	no	Optional LOD index to query (default 0)

Returns: { static_mesh_path, lod_index, surface_area, volume, center_of_mass_x, center_of_mass_y, center_of_mass_z, is_closed }

get_num_connected_islands

Read-only.

Get the number of separate connected components in the mesh (alias of GetNumConnectedComponents).

Parameter	Type	Required	Description
actor_name	string	yes	DynamicMeshActor name (required)

Returns: { actor_name, num_connected_islands }

get_num_extended_polygroup_layers

Read-only.

Count the extended polygroup layers (those beyond the default polygroup layer) on a DynamicMeshActor's live dynamic mesh in the editor world, as num_polygroup_layers. Read-only; reply actor_name is the component name, not the actor label. Change the count with set_num_extended_polygroup_layers.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the target DynamicMeshActor in the editor world.

Returns: { actor_name, num_polygroup_layers }

get_num_open_border_edges

Read-only.

Count the open boundary edges (edges with a single adjacent triangle) of a DynamicMeshActor's live dynamic mesh in the editor world; 0 means the mesh is closed. Read-only; get the loops with get_mesh_open_border_loops. Reply actor_name is the component name, not the actor label.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the target DynamicMeshActor in the editor world.

Returns: { actor_name, num_open_border_edges }

get_num_uv_islands

Read-only.

Get the number of UV islands in a UV channel.

Parameter	Type	Required	Description
actor_name	string	yes	DynamicMeshActor name (required)
uv_channel	number	yes	UV channel index (required)

Returns: { actor_name, uv_channel, num_uv_islands, is_valid_uv_channel }

is_bvh_valid_for_mesh

Read-only.

Report whether a BVH built for the live dynamic mesh of a DynamicMeshActor in the editor world is valid for it, via BuildBVHForMesh then UGeometryScriptLibrary_MeshSpatial::IsBVHValidForMesh. The plugin keeps no BVH between calls (build_mesh_bvh and rebuild_mesh_bvh drop theirs, and the spatial-query tools build their own on every call), so no kept BVH can go stale after a mesh edit and that staleness is not tracked: this builds a BVH for the mesh as it is now and checks it, as each spatial query does. bvh_valid false means no valid BVH could be built for the mesh. The mesh is not changed.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.

Returns: { actor_name, bvh_valid: bool } -- actor_name is the dynamic mesh component's name, not the actor label.

is_point_inside_mesh

Read-only.

Test whether a 3D point is inside the live dynamic mesh of a DynamicMeshActor using Fast Winding Number via UGeometryScriptLibrary_MeshSpatial::IsPointInsideMesh. Every call builds a fresh BVH and fast winding tree from the mesh as it is now (the plugin keeps none), so the answer always reflects the latest mesh edits. The mesh is not changed.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
query_point	array	no	[x, y, z] point in the mesh's local space.
winding_threshold	number	no	Optional float; default 0.5 (standard parity test). Higher values shrink the "inside" region.
max_distance	number	no	Optional float; it has no effect on this query, whose winding-number test uses no search distance.
allow_unsafe_modified	boolean	no	Optional; maps to bAllowUnsafeModifiedQueries (default false). It has no effect: the BVH is built fresh on every call, so it always matches the mesh.

Returns: { actor_name, is_inside: bool, containment_outcome: string } -- actor_name is the dynamic mesh component's name, not the actor label.

rebuild_mesh_bvh

Read-only.

Build a BVH for the live dynamic mesh of a DynamicMeshActor with RebuildBVHForMesh and read it back with IsBVHValidForMesh. The BVH is a temporary that is not kept: the spatial-query tools build their own on every call, so this only checks that a BVH can be built for the mesh as it is now. bvh_rebuilt is true when the engine reported no error and the BVH reads back as valid; the call fails otherwise. The mesh is not changed.

Parameter	Type	Required	Description
actor_name	string	yes	DynamicMeshActor name (required)
b_only_if_invalid	boolean	no	Optional, default true; it has no effect, since every call starts from an empty temporary BVH that the engine always rebuilds

Returns: { actor_name, bvh_rebuilt: bool, b_only_if_invalid, bvh_valid } -- actor_name is the dynamic mesh component's name, not the actor label.

recompute_mesh_normals

Destructive, idempotent.

Recompute the normals of the live dynamic mesh of a DynamicMeshActor in the editor world, overwriting the values of its existing normal overlay while keeping its hard-edge splits; a mesh without normals first gets per-vertex normals. Face contributions are weighted by area and by corner angle (both on by default; both off gives a plain average). Idempotent, in an editor transaction, nothing saved. An empty mesh is an error, and recomputed is false (the call fails) when the engine reports an error. Use it when shading looks wrong after geometry edits; copy_dynamic_mesh_to_static_mesh persists the result.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
angle_weighted	boolean	no	Weight contributing face normals by corner angle, default true
area_weighted	boolean	no	Weight contributing face normals by face area, default true

Returns: { actor_name: string, angle_weighted: bool, area_weighted: bool, triangle_count: int, vertex_count: int, recomputed: bool }

recompute_mesh_uvs

Destructive.

Recompute UVs on a UV channel using the configured flatten method. A channel the mesh does not have, or an empty mesh, is an error; recomputed is false, and the call fails, when the engine refuses (for example polygroups on a mesh without polygroups).

Parameter	Type	Required	Description
actor_name	string	yes	DynamicMeshActor name (required)
uv_channel	number	no	UV channel index (default 0)
island_source	string	no	"uv_islands" | "polygroups" | "existing_groups" | "selection" (default "uv_islands")
method	string	no	flatten method: "spectral_conformal" (default), "conformal" or "exp_map"

Returns: { actor_name, uv_channel, island_source, method, recomputed }

remap_material_ids

Destructive.

Renumber MaterialIDs on a DynamicMeshActor's live dynamic mesh. Two modes: pass from_material_id + to_material_id to merge one ID into another (UGeometryScriptLibrary_MeshMaterialFunctions::RemapMaterialIDs), or pass compact=true with the material list to close gaps left by deleted/merged IDs (CompactMaterialIDs) and get back the compacted list to hand to copy_dynamic_mesh_to_static_mesh. Gaps matter: MaterialIDs index into that list positionally, so an unused ID in the middle costs a wasted material slot on the baked asset. The materials list may be shorter than the IDs in use (or absent): the missing entries count as no material. When no triangle carries from_material_id, or from and to are the same ID, the mesh is left unchanged and the call succeeds with applied false, triangles_remapped 0 and a note. Otherwise applied is measured (remap: the triangles that carried from_material_id no longer do; compact: the engine reported no error) and the call fails when it is false.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
compact	boolean	no	Compact mode: renumber IDs to be contiguous from 0 (default false).
from_material_id	number	no	Remap mode: the MaterialID to replace. Required unless compact is true.
to_material_id	number	no	Remap mode: the MaterialID to replace it with. Required unless compact is true.
materials	array	no	Compact mode: ordered UMaterialInterface content paths, one per current MaterialID. The compacted list is returned in compacted_materials, in the new ID order.
remove_duplicate_materials	boolean	no	Compact mode: also merge IDs that point at the SAME material asset (default false).

Returns: { actor_name, mode: string, from_material_id: int, to_material_id: int, triangles_remapped?: int, max_material_id_after: int, distinct_material_ids_after: int, compacted_materials: [string], applied: bool, note?: string }

remove_dynamic_mesh_actor

Destructive.

Destroy a DynamicMeshActor in the editor world, found by label or object name, inside an undoable transaction. Returns the label, internal name and triangle_count_before of the destroyed actor; fails if the name matches no DynamicMeshActor. Create one with spawn_dynamic_mesh_actor.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the DynamicMeshActor to destroy.

Returns: { actor_name: string, actor_internal_name: string, destroyed: bool, triangle_count_before: int, note?: string }

remove_unused_vertices

Destructive.

Remove the vertices no triangle references from a DynamicMeshActor's live dynamic mesh in the editor world and refresh its render data. Remaining vertex IDs are not renumbered and a clean mesh is a no-op; returns vertex_count_before, vertex_count, vertices_removed and removed.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the target DynamicMeshActor in the editor world.

Returns: { actor_name: string, triangle_count: int, vertex_count: int, vertex_count_before: int, vertices_removed: int, removed: bool }

repack_mesh_uvs

Destructive.

Pack existing UV islands on a UV channel into standard UV space. A channel the mesh does not have, or an empty mesh, is an error checked before anything changes. A channel with no UVs set has no islands to pack: the call succeeds with repacked false and a note, leaving the mesh unchanged. Otherwise repacked is false, and the call fails, when the engine reports an error. No undo entry, nothing saved.

Parameter	Type	Required	Description
actor_name	string	yes	DynamicMeshActor name (required)
uv_channel	number	no	UV channel index (default 0)
target_image_width	number	no	target image width in pixels (default 512)
optimize_island_rotation	boolean	no	whether to optimize island rotation (default true)

Returns: { actor_name, uv_channel, target_image_width, optimize_island_rotation, num_uv_islands, repacked, note? }

repair_mesh_self_intersections

Destructive.

Boolean-union a DynamicMeshActor's dynamic mesh with itself to repair self-intersections, remove internal/floating geometry and resolve non-manifold overlaps (UGeometryScriptLibrary_MeshBooleanFunctions::ApplyMeshSelfUnion). Convergent: the first pass mutates the mesh, but a second pass on the already-cleaned mesh is a no-op (repaired reports false). NOTE: the engine impl ignores its internal success flag and always returns the target mesh, so success is measured by comparing the triangle count, not by the return value.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor (mutated in place)
fill_holes	boolean	no	Optional bool override for FGeometryScriptMeshSelfUnionOptions.bFillHoles (default true)
trim_flaps	boolean	no	Optional bool override for FGeometryScriptMeshSelfUnionOptions.bTrimFlaps (default true)
simplify_output	boolean	no	Optional bool override for FGeometryScriptMeshSelfUnionOptions.bSimplifyOutput (default true)
winding_threshold	number	no	Optional [0..1] float override for FGeometryScriptMeshSelfUnionOptions.WindingThreshold (default 0.5). Space with generalised winding number above this is considered inside.

Returns: { actor_name: string, triangle_count: int, triangle_count_before: int, vertex_count: int, is_closed: bool, repaired: bool }

rotate_dynamic_mesh

Destructive.

Rotate every vertex of the live dynamic mesh of a DynamicMeshActor in the editor world about the mesh-local origin, baking the rotation into the geometry; the actor transform is not touched. Rotations accumulate: each call turns the current mesh again. Runs in an editor transaction, nothing saved. An empty mesh is an error; a zero rotation succeeds with applied false and a note, leaving the mesh unchanged. Use transform_dynamic_mesh to move, rotate and scale in one call, set_actor_transform to turn the actor itself, rotate_mesh_uvs to rotate UVs.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
rotation	array	yes	[pitch, yaw, roll] Euler rotation in degrees, applied on top of the current mesh

Returns: { actor_name: string, rotation_pitch: number, rotation_yaw: number, rotation_roll: number, applied: bool, note?: string }

rotate_mesh_uvs

Destructive.

Rotate all UVs of one channel on a DynamicMeshActor's live dynamic mesh in the editor world by an angle in degrees around a UV-space pivot; 0 degrees changes nothing (rotated false). No undo entry; reply actor_name is the component name, not the actor label.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the target DynamicMeshActor in the editor world.
uv_channel	number	yes	0-based UV channel index; a channel the mesh does not have fails the call.
rotation_angle_deg	number	yes	Rotation angle in degrees; 0 leaves the UVs untouched.
rotation_origin_u	number	no	U coordinate of the rotation pivot (default 0).
rotation_origin_v	number	no	V coordinate of the rotation pivot (default 0).

Returns: { actor_name, uv_channel, rotation_angle_deg, rotation_origin: {u, v}, rotated: bool }

scale_dynamic_mesh

Destructive.

Scale the live dynamic mesh of a DynamicMeshActor via UGeometryScriptLibrary_MeshTransformFunctions::ScaleMesh, in an editor transaction. A scale that is not three numbers, or an empty mesh, is an error. A scale of 1,1,1 succeeds with applied false and a note, leaving the mesh unchanged.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
scale	array	no	[x, y, z] scale factor (1.0 = no change)

Returns: { actor_name: string, scale_x: number, scale_y: number, scale_z: number, applied: bool, note?: string }

scale_mesh_uvs

Destructive.

Scale all UVs of one channel on a DynamicMeshActor's live dynamic mesh in the editor world by separate U and V factors; zero factors are refused and 1, 1 changes nothing (scaled false). No undo entry; reply actor_name is the component name, not the actor label.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the target DynamicMeshActor in the editor world.
uv_channel	number	yes	0-based UV channel index; a channel the mesh does not have fails the call.
scale_u	number	yes	Scale factor along U; must be non-zero (1 keeps U unchanged).
scale_v	number	yes	Scale factor along V; must be non-zero (1 keeps V unchanged).
scale_origin_u	number	no	U coordinate of the point the scaling is centred on (default 0).
scale_origin_v	number	no	V coordinate of the point the scaling is centred on (default 0).

Returns: { actor_name: string, uv_channel: int, scale_u: number, scale_v: number, scale_origin: { u, v }, scaled: bool }

select_mesh_triangles

Destructive.

Resolve a region into a triangle selection and REPORT it, without modifying anything. Read-only companion of set_mesh_material_id_in_region: same region parameters, same resolver, so a region previewed here paints exactly those triangles there. Use it to avoid the failure mode where a mis-specified box selects 0 triangles and the paint call still returns success. Coordinates are LOCAL to the dynamic mesh, not world.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
region	string	no	'all' (default) | 'box' | 'sphere' | 'plane' | 'normal_angle' | 'material_id' | 'polygroup' | 'connected_component' (one physical PIECE, by the island index that get_mesh_components_detail reports).
center	array	no	Local [x,y,z] centre. Used by box/sphere, and as the plane origin.
extent	array	no	Local [x,y,z] HALF-size in cm. Required by region='box'.
radius	number	no	Radius in cm. Required by region='sphere'.
normal	array	no	[x,y,z] direction. Plane normal for region='plane', facing direction for 'normal_angle'. Default [0,0,1].
max_angle_deg	number	no	Max angle from normal in degrees for region='normal_angle' (default 15).
source_material_id	integer	no	MaterialID to select when region='material_id'.
polygroup_id	integer	no	Polygroup to select when region='polygroup'.
polygroup_layer	integer	no	Optional extended polygroup layer index for region='polygroup'.
component_index	integer	no	Island index when region='connected_component'. Get it from get_mesh_components_detail, which reports each piece's size and bounding box.
min_triangle_points	integer	no	How many of a triangle's 3 points must be inside for it to count, 1-3 (default 3 = fully contained).
invert	boolean	no	Invert the spatial selection (default false).
include_triangle_ids	boolean	no	Also return the resolved triangle IDs (default false; they can be thousands). The returned array is what set_mesh_material_id scope='triangles' consumes.
max_triangle_ids	number	no	Cap on how many IDs to return when include_triangle_ids is on (default 1000). When the cap truncates, triangle_ids_truncated is true — the count in triangles_selected is still the real one.

Returns: { actor_name, region, triangles_selected: int, mesh_triangle_count: int, is_empty: bool, triangle_ids: [int], triangle_ids_truncated: bool }

set_dynamic_mesh_material

Destructive, idempotent.

Assign a UMaterialInterface asset to a slot on a DynamicMeshActor's UDynamicMeshComponent, in an editor transaction. applied is the slot read back after the assignment; the call fails when it does not hold the material.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor (required).
material_path	string	yes	Asset path of the UMaterialInterface (e.g. /Engine/EngineMaterials/DefaultMaterial) (required).
slot_index	number	no	Material slot to assign. Default 0 (the dynamic mesh only uses slot 0).

Returns: { actor_name: string, material_path: string, material_name: string, slot_index: int, applied: bool, note?: string }

set_mesh_material_id

Destructive, idempotent.

Stamp a MaterialID onto triangles of a DynamicMeshActor's live dynamic mesh. scope='all' repaints every triangle (UGeometryScriptLibrary_MeshMaterialFunctions::ClearMaterialIDs); scope='triangles' repaints the listed triangle IDs (SetMaterialIDOnTriangles). Calls EnableMaterialIDs first, because on a mesh without that attribute the engine drops the write. An ID in triangle_ids that is not a triangle, or an empty mesh, is an error checked before anything is painted. The targeted triangles are read back: applied is true when all of them carry material_id, and the call fails otherwise.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
material_id	number	no	MaterialID to write (>= 0). Index into the material list later passed to copy_dynamic_mesh_to_static_mesh.
scope	string	no	'all' (default) or 'triangles'.
triangle_ids	array	no	Required when scope='triangles': array of triangle IDs to repaint (e.g. from select_mesh_triangles).

Returns: { actor_name, material_id, scope, triangles_targeted: int, triangles_painted: int, max_material_id_after: int, distinct_material_ids_after: int, applied: bool }

set_mesh_material_id_in_region

Destructive, idempotent.

Stamp a MaterialID onto every triangle inside a region, via the engine's SelectMeshElements* family + SetMaterialIDForMeshSelection. Use this when polygroups are not usable — after a boolean, appended pieces are fused and set_polygroup_material_id cannot address them separately. Coordinates are LOCAL to the dynamic mesh, not world. Preview any region with select_mesh_triangles before painting: a region that selects 0 triangles still returns success.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
material_id	number	no	MaterialID to write (>= 0).
region	string	no	'all' (default) | 'box' | 'sphere' | 'plane' | 'normal_angle' | 'material_id' | 'polygroup' | 'connected_component' (one physical PIECE, by the island index that get_mesh_components_detail reports).
center	array	no	Local [x,y,z] centre. Used by box/sphere, and as the plane origin.
extent	array	no	Local [x,y,z] HALF-size in cm. Required by region='box'.
radius	number	no	Radius in cm. Required by region='sphere'.
normal	array	no	[x,y,z] direction. Plane normal for region='plane', facing direction for 'normal_angle'. Default [0,0,1].
max_angle_deg	number	no	Max angle from normal in degrees for region='normal_angle' (default 15).
source_material_id	integer	no	The MaterialID to SELECT when region='material_id'. Separate from material_id, which is the one being written, so 'repaint 1 as 2' is expressible.
polygroup_id	integer	no	Polygroup to select when region='polygroup'.
polygroup_layer	integer	no	Optional extended polygroup layer index for region='polygroup'.
component_index	integer	no	Island index when region='connected_component'. Get it from get_mesh_components_detail, which reports each piece's size and bounding box.
min_triangle_points	integer	no	How many of a triangle's 3 points must be inside for it to count, 1-3 (default 3 = fully contained). Only used by the spatial regions.
invert	boolean	no	Invert the spatial selection (default false).

Returns: { actor_name, material_id, region, triangles_selected: int, max_material_id_after: int, distinct_material_ids_after: int, applied: bool }

set_mesh_uv_element_position

Destructive, idempotent.

Set the (u, v) of one element of a UV channel overlay on a DynamicMeshActor's live dynamic mesh in the editor world; an invalid element ID writes nothing and returns is_valid_element false, not an error. No undo entry; reply actor_name is the component name, not the actor label.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the target DynamicMeshActor in the editor world.
uv_channel	number	yes	0-based UV channel index; a channel the mesh does not have fails the call.
element_id	number	yes	ID of the element in the UV overlay of that channel, not a vertex, edge or triangle ID.
u	number	yes	New U coordinate of the element.
v	number	yes	New V coordinate of the element.

Returns: { actor_name, uv_channel, element_id, new_position: {u, v}, is_valid_element, set: bool }

set_mesh_uvs_from_projection

Destructive, idempotent.

Replace the UVs of one channel on a DynamicMeshActor's live dynamic mesh in the editor world with a box, plane or cylinder projection, optionally only inside a region. Box suits plank-and-post geometry (each face takes the axis it faces), plane only flat pieces, cylinder wrapped shapes. Returns triangles_affected and applied.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
projection	string	no	'box' (default) | 'plane' | 'cylinder'.
uv_channel	number	no	UV channel to write (default 0).
location	array	no	Local [x,y,z] origin of the projection shape (default the mesh origin).
rotation	array	no	[pitch, yaw, roll] of the projection shape (default none). For 'plane', this is what chooses which way the plane faces.
scale	array	no	[x,y,z] size of the projection shape (default [100,100,100]). THIS IS THE UV DENSITY KNOB: bigger scale = texture repeats fewer times. A tileable material that reads too big or too small is fixed here, not in the material.
min_island_tri_count	number	no	box only: islands smaller than this are merged into a neighbour (default 2).
split_angle	number	no	cylinder only: angle in degrees at which the wrap is split (default 45).
region	string	no	Optional region to limit the projection to; same vocabulary as select_mesh_triangles (default 'all').
component_index	integer	no	Island index when region='connected_component'.
center	array	no	Region parameter (box/sphere centre, plane origin).
extent	array	no	Region parameter: box HALF-size.
radius	number	no	Region parameter: sphere radius.
normal	array	no	Region parameter: plane/normal_angle direction.
max_angle_deg	number	no	Region parameter for region='normal_angle'.
source_material_id	integer	no	Region parameter for region='material_id'.
polygroup_id	integer	no	Region parameter for region='polygroup'.
polygroup_layer	integer	no	Region parameter for region='polygroup': extended polygroup layer index (default the mesh's default polygroup layer).
min_triangle_points	integer	no	Region parameter, 1-3.
invert	boolean	no	Select the complement of a box, sphere, plane or normal_angle region (default false); the other regions ignore it.

Returns: { actor_name, projection, uv_channel, region, triangles_affected: int, uv_channel_count: int, applied: bool }

set_num_extended_polygroup_layers

Destructive, idempotent.

Set the number of extended polygroup layers on the live dynamic mesh of a DynamicMeshActor via UGeometryScriptLibrary_MeshPolygroupFunctions::SetNumExtendedPolygroupLayers. Idempotent: the engine dedups (only reshapes attributes when the count actually differs from the current one), so re-setting the same count is a no-op. The layer count is read back AFTER the set via GetNumExtendedPolygroupLayers: applied is true when it equals the request, and the call fails when it does not.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
num_layers	number	no	Desired number of extended polygroup layers (>= 0).

Returns: { actor_name, requested_num_layers, num_polygroup_layers, applied: bool }

set_num_uv_channels

Destructive, idempotent.

Set how many UV channels the live dynamic mesh of a DynamicMeshActor in the editor world has: added channels start without UVs, and channels from num_uv_channels upward are discarded with their UVs (note says so). The current count is a no-op (changed false). The engine allows at most 8, so a count above 8 is an error; num_uv_channels is the count read back after the call, and the call fails if it differs from the request. No undo entry, nothing saved; reply actor_name is the component name, not the actor label. Fill a channel with copy_mesh_uv_channel or generate_mesh_uvs; clear_uv_channel works on static mesh assets.

Parameter	Type	Required	Description
actor_name	string	yes	DynamicMeshActor name (required)
num_uv_channels	number	yes	Desired count, 0 to 8 (required)

Returns: { actor_name: string, num_uv_channels: int, previous_num_uv_channels: int, changed: bool, note?: string } -- actor_name is the dynamic mesh component's name, not the actor label; num_uv_channels is read back; note when channels were removed, whose UV data is dropped.

set_polygroup_material_id

Destructive, idempotent.

Stamp a MaterialID onto every triangle of one polygroup via UGeometryScriptLibrary_MeshMaterialFunctions::SetPolygroupMaterialID. This is usually the cheapest way to paint a part: append_mesh_primitive lays primitives down with PerFace polygroups, so each appended piece is already its own group. HONEST GATE: the engine reports whether the polygroup ID actually existed, and that flag is surfaced as polygroup_id_valid — a false there means nothing was painted, even though the call succeeded.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor.
polygroup_id	number	no	Polygroup ID to repaint.
material_id	number	no	MaterialID to write (>= 0).
polygroup_layer	number	no	Optional extended polygroup layer index. Omit for the default layer.

Returns: { actor_name, polygroup_id, material_id, polygroup_id_valid: bool, max_material_id_after: int, distinct_material_ids_after: int, applied: bool }

simplify_mesh

Destructive.

QEM-simplify a DynamicMeshActor's dynamic mesh to a target triangle count

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
target_triangle_count	number	yes	Target triangle count to simplify down to (must be > 0)

Returns: { actor_name: string, target_triangle_count: int, triangle_count_before: int, triangle_count_after: int, vertex_count: int, simplified: bool }

spawn_dynamic_mesh_actor

Destructive.

Spawn an empty ADynamicMeshActor into the editor world (not PIE) at an optional location and rotation, ignoring collisions, in an undoable transaction. Returns the label of the new actor as actor_name, its internal name and triangle_count (0). Remove it with remove_dynamic_mesh_actor.

Parameter	Type	Required	Description
location	array	no	World location [x, y, z] in cm (default the world origin).
rotation	array	no	World rotation in degrees as [pitch, yaw, roll] (default no rotation).

Returns: { actor_name: string, actor_internal_name: string, actor_class: string, has_dynamic_mesh_component: bool, has_dynamic_mesh: bool, triangle_count: int, spawned: bool }

transform_dynamic_mesh

Destructive.

Apply a full FTransform (translation + rotation + scale) to the live dynamic mesh of a DynamicMeshActor via UGeometryScriptLibrary_MeshTransformFunctions::TransformMesh, in an editor transaction. A location or scale that is not three numbers, or an empty mesh, is an error. An identity transform succeeds with applied false and a note, leaving the mesh unchanged.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
location	array	no	Optional [x, y, z] translation; default (0,0,0)
rotation	array	no	Optional [pitch, yaw, roll] rotation; default (0,0,0)
scale	array	no	Optional [x, y, z] scale; default (1,1,1)

Returns: { actor_name: string, location_x: number, location_y: number, location_z: number, rotation_pitch: number, rotation_yaw: number, rotation_roll: number, scale_x: number, scale_y: number, scale_z: number, applied: bool, note?: string }

translate_dynamic_mesh

Destructive.

Translate the live dynamic mesh of a DynamicMeshActor via UGeometryScriptLibrary_MeshTransformFunctions::TranslateMesh, in an editor transaction. A translation that is not three numbers, or an empty mesh, is an error. A zero translation succeeds with applied false and a note, leaving the mesh unchanged.

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
translation	array	no	[x, y, z] translation delta in local space

Returns: { actor_name: string, translation_x: number, translation_y: number, translation_z: number, applied: bool, note?: string }

translate_mesh_uvs

Destructive.

Offset all UVs of one channel on a DynamicMeshActor's live dynamic mesh in the editor world by (translate_u, translate_v); a zero offset changes nothing (translated false). No undo entry; reply actor_name is the component name, not the actor label.

Parameter	Type	Required	Description
actor_name	string	yes	Label or object name (case-insensitive) of the target DynamicMeshActor in the editor world.
uv_channel	number	yes	0-based UV channel index; a channel the mesh does not have fails the call.
translate_u	number	yes	Offset added to every U coordinate (1.0 shifts by one full tile).
translate_v	number	yes	Offset added to every V coordinate (1.0 shifts by one full tile).

Returns: { actor_name: string, uv_channel: int, translate_u: number, translate_v: number, translated: bool }

weld_mesh_edges

Destructive.

Weld coincident open boundary edges of a DynamicMeshActor's dynamic mesh

Parameter	Type	Required	Description
actor_name	string	yes	Label or name of the target DynamicMeshActor
tolerance	number	no	Coincident-edge distance threshold in mesh units (default 1e-06)
only_unique_pairs	boolean	no	Only merge unambiguous pairs with unique duplicate-edge matches (default true)

Returns: { actor_name: string, tolerance: number, only_unique_pairs: bool, triangle_count: int, vertex_count: int, welded: bool }