Generate KHR_mesh_primitive_restart samples

gen-primitive-restart-samples.ts

import { Document, NodeIO, type vec3 } from '@gltf-transform/core';
import { KHRMaterialsUnlit, KHRMeshPrimitiveRestart } from '@gltf-transform/extensions';
import { join } from '@gltf-transform/functions';

// NOTE: Package '@gltf-transform/test-utils' is a private package within the glTF Transform
// GitHub repo, not published to npm. This script must either be run within the repo's workspace,
// or linked (npm link, yarn link, etc.) to the package locally.
import {
	createLineLoopPrim,
	createLineStripPrim,
	createTriangleStripPrim,
	createTriangleFanPrim,
} from '@gltf-transform/test-utils';

const io = new NodeIO().registerExtensions([KHRMaterialsUnlit, KHRMeshPrimitiveRestart]);

const OUTPUT_DIR = './primitive-restart-samples';

type PrimFactory = {
	name: string;
	translate: (i: number) => vec3;
	scale: (i: number) => vec3;
	fn: typeof createLineStripPrim;
};

const PRIM_FACTORIES: PrimFactory[] = [
	{
		name: 'line-strip',
		translate: (i: number) => [(i % 3) - 1, Math.floor(i / 3) - 1, 0],
		scale: (_: number) => [0.333, 0.333, 0.333],
		fn: createLineStripPrim,
	},
	{
		name: 'line-loop',
		translate: (i: number) => [(i % 3) - 1, Math.floor(i / 3) - 1, 0],
		scale: (_: number) => [0.333, 0.333, 0.333],
		fn: createLineLoopPrim,
	},
	{
		name: 'triangle-strip',
		translate: (i: number) => [i - 4, 0, 0],
		scale: (_: number) => [0.333, 0.333, 0.333],
		fn: createTriangleStripPrim,
	},
	{
		name: 'triangle-fan',
		translate: (i: number) => [(i % 3) - 1, Math.floor(i / 3) - 1, 0],
		scale: (_: number) => [0.333, 0.333, 0.333],
		fn: createTriangleFanPrim,
	},
];

for (const factory of PRIM_FACTORIES) {
	const document = new Document();
	const mesh = document.createMesh();
	const node = document.createNode().setMesh(mesh);
	const scene = document.createScene().addChild(node);
	document.getRoot().setDefaultScene(scene);

	const unlitExtension = document.createExtension(KHRMaterialsUnlit);
	const unlit = unlitExtension.createUnlit();
	const material = document.createMaterial().setExtension('KHR_materials_unlit', unlit);

	for (let i = 0; i < 9; i++) {
		const prim = factory.fn(document, 8, factory.translate(i), factory.scale(i));
		prim.setMaterial(material);
		mesh.addPrimitive(prim);
	}

	await document.transform(join());
	await io.write(`${OUTPUT_DIR}/primitive-restart-${factory.name}.glb`, document);
}