Function instance

packages/functions/src/instance.ts:45–145

(_options: InstanceOptions = INSTANCE_DEFAULTS)

 * @category Transforms
 */
export function instance(_options: InstanceOptions = INSTANCE_DEFAULTS): Transform {
	const options = assignDefaults(INSTANCE_DEFAULTS, _options);

	return createTransform(NAME, (doc: Document): void => {
		const logger = doc.getLogger();
		const root = doc.getRoot();

		if (root.listAnimations().length) {
			logger.warn(`${NAME}: Instancing is not currently supported for animated models.`);
			logger.debug(`${NAME}: Complete.`);
			return;
		}

		const batchExtension = doc.createExtension(EXTMeshGPUInstancing);

		let numBatches = 0;
		let numInstances = 0;

		for (const scene of root.listScenes()) {
			// Gather a one-to-many Mesh/Node mapping, identifying what we can instance.
			const meshInstances = new Map<Mesh, Set<Node>>();
			scene.traverse((node) => {
				const mesh = node.getMesh();
				if (!mesh) return;
				if (node.getExtension('EXT_mesh_gpu_instancing')) return;
				meshInstances.set(mesh, (meshInstances.get(mesh) || new Set<Node>()).add(node));
			});

			// For each Mesh, create an InstancedMesh and collect transforms.
			const modifiedNodes = [];
			for (const mesh of Array.from(meshInstances.keys())) {
				const nodes = Array.from(meshInstances.get(mesh)!);
				if (nodes.length < options.min) continue;
				if (nodes.some((node) => node.getSkin())) continue;

				// Cannot preserve volumetric effects when instancing with varying scale.
				// See: https://github.com/KhronosGroup/glTF-Sample-Models/tree/master/2.0/AttenuationTest
				if (mesh.listPrimitives().some(hasVolume) && nodes.some(hasScale)) continue;

				const batch = createBatch(doc, batchExtension, mesh, nodes.length);
				const batchTranslation = batch.getAttribute('TRANSLATION')!;
				const batchRotation = batch.getAttribute('ROTATION')!;
				const batchScale = batch.getAttribute('SCALE')!;

				const batchNode = doc.createNode().setMesh(mesh).setExtension('EXT_mesh_gpu_instancing', batch);
				scene.addChild(batchNode);

				let needsTranslation = false;
				let needsRotation = false;
				let needsScale = false;

				// For each Node, write TRS properties into instance attributes.
				for (let i = 0; i < nodes.length; i++) {
					let t: vec3, r: vec4, s: vec3;
					const node = nodes[i];

					batchTranslation.setElement(i, (t = node.getWorldTranslation()));
					batchRotation.setElement(i, (r = node.getWorldRotation()));