three.js/src/renderers/webgl/WebGLObjects.js

function WebGLObjects( gl, geometries, attributes, info ) {

	let updateMap = new WeakMap();

	function update( object ) {

		const frame = info.render.frame;

		const geometry = object.geometry;
		const buffergeometry = geometries.get( object, geometry );

		// Update once per frame

		if ( updateMap.get( buffergeometry ) !== frame ) {

			geometries.update( buffergeometry );

			updateMap.set( buffergeometry, frame );

		}

		if ( object.isInstancedMesh ) {

			if ( object.hasEventListener( 'dispose', onInstancedMeshDispose ) === false ) {

				object.addEventListener( 'dispose', onInstancedMeshDispose );

			}

			attributes.update( object.instanceMatrix, gl.ARRAY_BUFFER );

			if ( object.instanceColor !== null ) {

				attributes.update( object.instanceColor, gl.ARRAY_BUFFER );

			}

		}

		if ( object.isSkinnedMesh ) {

			// update skeleton only once in a frame

			if ( object.skeleton.frame !== info.render.frame ) {

				object.skeleton.update();
				object.skeleton.frame = info.render.frame;

			}

		}


		return buffergeometry;

	}

	function dispose() {

		updateMap = new WeakMap();

	}

	function onInstancedMeshDispose( event ) {

		const instancedMesh = event.target;

		instancedMesh.removeEventListener( 'dispose', onInstancedMeshDispose );

		attributes.remove( instancedMesh.instanceMatrix );

		if ( instancedMesh.instanceColor !== null ) attributes.remove( instancedMesh.instanceColor );

	}

	return {

		update: update,
		dispose: dispose

	};

}


export { WebGLObjects };