fix(functions): Ensure quantize() creates required instance TRS attri…

…butes for EXT_mesh_gpu_instancing

packages/functions/src/quantize.ts

@@ -200,13 +200,13 @@ export function quantize(_options: QuantizeOptions = QUANTIZE_DEFAULTS): Transfo
 }
 
 function quantizePrimitive(
-	doc: Document,
+	document: Document,
 	prim: Primitive | PrimitiveTarget,
 	nodeTransform: VectorTransform<vec3>,
 	options: Required<QuantizeOptions>,
 ): void {
 	const isTarget = prim instanceof PrimitiveTarget;
-	const logger = doc.getLogger();
+	const logger = document.getLogger();
 
 	for (const semantic of prim.listSemantics()) {
 		if (!isTarget && !options.pattern.test(semantic)) continue;
@@ -280,7 +280,7 @@ function getNodeTransform(volume: bbox): VectorTransform<vec3> {
 }
 
 /** Applies corrective scale and offset to nodes referencing a quantized Mesh. */
-function transformMeshParents(doc: Document, mesh: Mesh, nodeTransform: VectorTransform<vec3>): void {
+function transformMeshParents(document: Document, mesh: Mesh, nodeTransform: VectorTransform<vec3>): void {
 	const transformMatrix = fromTransform(nodeTransform);
 	for (const parent of mesh.listParents()) {
 		if (!(parent instanceof Node)) continue;
@@ -297,13 +297,13 @@ function transformMeshParents(doc: Document, mesh: Mesh, nodeTransform: VectorTr
 
 		const batch = parent.getExtension<InstancedMesh>('EXT_mesh_gpu_instancing');
 		if (batch) {
-			parent.setExtension('EXT_mesh_gpu_instancing', transformBatch(batch, nodeTransform));
+			parent.setExtension('EXT_mesh_gpu_instancing', transformBatch(document, batch, nodeTransform));
 			continue;
 		}
 
 		let targetNode: Node;
 		if (isParentNode || isAnimated) {
-			targetNode = doc.createNode('').setMesh(mesh);
+			targetNode = document.createNode('').setMesh(mesh);
 			parent.addChild(targetNode).setMesh(null);
 			animChannels
 				.filter((channel) => channel.getTargetPath() === WEIGHTS)
@@ -333,21 +333,34 @@ function transformSkin(skin: Skin, nodeTransform: VectorTransform<vec3>): Skin {
 }
 
 /** Applies corrective scale and offset to GPU instancing batches. */
-function transformBatch(batch: InstancedMesh, nodeTransform: VectorTransform<vec3>): InstancedMesh {
+function transformBatch(document: Document, batch: InstancedMesh, nodeTransform: VectorTransform<vec3>): InstancedMesh {
 	if (!batch.getAttribute('TRANSLATION') && !batch.getAttribute('ROTATION') && !batch.getAttribute('SCALE')) {
 		return batch;
 	}
 
 	batch = batch.clone(); // quantize() does cleanup.
-	const instanceTranslation = batch.getAttribute('TRANSLATION')?.clone();
+
+	let instanceTranslation = batch.getAttribute('TRANSLATION')?.clone();
 	const instanceRotation = batch.getAttribute('ROTATION')?.clone();
-	const instanceScale = batch.getAttribute('SCALE')?.clone();
+	let instanceScale = batch.getAttribute('SCALE')?.clone();
+
 	const tpl = (instanceTranslation || instanceRotation || instanceScale)!;
 
 	const T_IDENTITY = [0, 0, 0] as vec3;
 	const R_IDENTITY = [0, 0, 0, 1] as vec4;
 	const S_IDENTITY = [1, 1, 1] as vec3;
 
+	// Transformed batch may now require instance translation or scale.
+	// See: https://github.com/donmccurdy/glTF-Transform/issues/1584
+
+	if (!instanceTranslation && nodeTransform.offset) {
+		instanceTranslation = document.createAccessor().setType('VEC3').setArray(makeArray(tpl.getCount(), T_IDENTITY));
+	}
+
+	if (!instanceScale && nodeTransform.scale) {
+		instanceScale = document.createAccessor().setType('VEC3').setArray(makeArray(tpl.getCount(), S_IDENTITY));
+	}
+
 	const t = [0, 0, 0] as vec3;
 	const r = [0, 0, 0, 1] as vec4;
 	const s = [1, 1, 1] as vec3;
@@ -608,3 +621,14 @@ function fromTransform(transform: VectorTransform<vec3>): mat4 {
 function clamp(value: number, range: vec2): number {
 	return Math.min(Math.max(value, range[0]), range[1]);
 }
+
+function makeArray(elementCount: number, initialElement: vec2 | vec3 | vec4) {
+	const elementSize = initialElement.length;
+	const array = new Float32Array(elementCount * elementSize);
+
+	for (let i = 0; i < elementCount; i++) {
+		array.set(initialElement, i * elementSize);
+	}
+
+	return array;
+}