Add InstancedMeshCulled implementation

Author: OndrejSpanel

src/Three.js

@@ -21,6 +21,7 @@ export { Skeleton } from './objects/Skeleton.js';
 export { Bone } from './objects/Bone.js';
 export { Mesh } from './objects/Mesh.js';
 export { InstancedMesh } from './objects/InstancedMesh.js';
+export { InstancedMeshCulled } from './objects/InstancedMeshCulled.js';
 export { LineSegments } from './objects/LineSegments.js';
 export { LineLoop } from './objects/LineLoop.js';
 export { Line } from './objects/Line.js';

src/objects/InstancedMeshCulled.js

@@ -0,0 +1,62 @@
+import { InstancedMesh } from './InstancedMesh.js';
+import { Sphere } from '../math/Sphere.js';
+import { Vector3 } from '../math/Vector3.js';
+
+
+class InstancedMeshCulled extends InstancedMesh {
+
+	constructor( geometry, material, count ) {
+
+		super( geometry, material, count );
+
+		this.frustumCulled = true;
+		this.boundingSphere =  null;
+
+	}
+
+	computeBoundingSphere() {
+
+		if (this.geometry.boundingSphere === null) this.geometry.computeBoundingSphere();
+
+		const min = new Vector3( Infinity, Infinity, Infinity );
+		const max = new Vector3( - Infinity, - Infinity, - Infinity );
+		const position = new Vector3();
+
+		for ( let m = 0; m < this.count; m ++ ) {
+
+			let x = this.instanceMatrix[ m * 16 + 12 ];
+			let y = this.instanceMatrix[ m * 16 + 13 ];
+			let z = this.instanceMatrix[ m * 16 + 14 ];
+			position.set( x, y, z );
+			min.min( position );
+			max.max( position );
+
+		}
+
+		let radius = 0;
+		const center = new Vector3().addVectors( min, max ).multiply( 0.5 );
+		for ( let m = 0; m < this.count; m ++ ) {
+
+			let x = this.instanceMatrix[ m * 16 + 12 ];
+			let y = this.instanceMatrix[ m * 16 + 13 ];
+			let z = this.instanceMatrix[ m * 16 + 14 ];
+			position.set( x, y, z );
+			const distance = position.distanceTo( center );
+			// note: we assume no scaling - computing scale from instance matrix is not trivial
+			const r = distance + this.geometry.boundingSphere.radius;
+			if ( r > radius ) radius = r;
+
+		}
+
+		this.boundingSphere = new Sphere( center, radius );
+
+	}
+
+	intersectsFrustum( frustum ) {
+
+		if (this.boundingSphere === null) this.computeBoundingSphere();
+		frustum.intersectsSphere( this.boundingSphere );
+
+	}
+
+}