feat: add Mesh.getVertexPosition()

- add `Mesh.getVertexPosition()`
- add doc comment of `SceneUtils.reduceVertices`

See: mrdoob/three.js#25049

Author: 0b5vr

types/three/examples/jsm/utils/SceneUtils.d.ts

@@ -15,6 +15,17 @@ export function createMeshesFromMultiMaterialMesh(mesh: Mesh): Group;
 
 export function sortInstancedMesh(mesh: InstancedMesh, compareFn: (a: number, b: number) => number): void;
 
+/**
+ * Akin to Array.prototype.reduce(), but operating on the vertices of all the visible descendant objects, in world space.
+ * Additionally, it can operate as a transform-reduce, returning a different type T than the Vector3 input.
+ * This can be useful for e.g. fitting a viewing frustum to the scene.
+ *
+ * @param object - The object to traverse (uses traverseVisible internally).
+ * @param func - The binary function applied for the reduction.
+ * Must have the signature: (value: T, vertex: Vector3): T.
+ * @param initialValue - The value to initialize the reduction with.
+ * This is required as it also sets the reduction type, which is not required to be Vector3.
+ */
 export function reduceVertices<TValue>(
     object: Object3D,
     func: (value: TValue, vertex: Vector3) => TValue,

types/three/src/objects/Mesh.d.ts

@@ -3,6 +3,7 @@ import { Raycaster } from './../core/Raycaster';
 import { Object3D } from './../core/Object3D';
 import { BufferGeometry } from '../core/BufferGeometry';
 import { Intersection } from '../core/Raycaster';
+import { Vector3 } from '../math/Vector3';
 
 export class Mesh<
     TGeometry extends BufferGeometry = BufferGeometry,
@@ -18,5 +19,12 @@ export class Mesh<
     type: string;
 
     updateMorphTargets(): void;
+
+    /**
+     * Get the current position of the indicated vertex in local space,
+     * taking into account the current animation state of both morph targets and skinning.
+     */
+    getVertexPosition(vert: number, target: Vector3): Vector3;
+
     raycast(raycaster: Raycaster, intersects: Intersection[]): void;
 }