BufferGeometryUtils: Add MikkTSpace version of .computeTangents() (#23716)

* BufferGeometryUtils: Add MikkTSpace version of .computeTangents()

* Lint

* BufferGeometryUtils: Fix .denormalize() usage.

examples/jsm/utils/BufferGeometryUtils.js

@@ -4,25 +4,91 @@ import {
 	Float32BufferAttribute,
 	InterleavedBuffer,
 	InterleavedBufferAttribute,
+	MathUtils,
 	TriangleFanDrawMode,
 	TriangleStripDrawMode,
 	TrianglesDrawMode,
-	Vector3
+	Vector3,
 } from 'three';
+import { generateTangents } from '../libs/mikktspace.module.js';
 
 
-function computeTangents( geometry ) {
+function computeTangents( geometry, negateSign = true ) {
 
-	geometry.computeTangents();
-	console.warn( 'THREE.BufferGeometryUtils: .computeTangents() has been removed. Use BufferGeometry.computeTangents() instead.' );
+	function getAttributeArray( attribute ) {
+
+		if ( attribute.normalized || attribute.isInterleavedBufferAttribute ) {
+
+			const srcArray = attribute.isInterleavedBufferAttribute ? attribute.data.array : attribute.array;
+			const dstArray = new Float32Array( attribute.getCount() * attribute.itemSize );
+
+			for ( let i = 0, j = 0; i < attribute.getCount(); i ++ ) {
+
+				dstArray[ j ++ ] = MathUtils.denormalize( attribute.getX( i ), srcArray );
+				dstArray[ j ++ ] = MathUtils.denormalize( attribute.getY( i ), srcArray );
+
+				if ( attribute.itemSize > 2 ) {
+
+					dstArray[ j ++ ] = MathUtils.denormalize( attribute.getZ( i ), srcArray );
+
+				}
+
+			}
+
+			return dstArray;
+
+		}
+
+		if ( attribute.array instanceof Float32Array ) {
+
+			return attribute.array;
+
+		}
+
+		return new Float32Array( attribute.array );
+
+	}
+
+	// MikkTSpace algorithm requires non-indexed input.
+
+	const _geometry = geometry.index ? geometry.toNonIndexed() : geometry;
+
+	// Compute vertex tangents.
+
+	const tangents = generateTangents(
+
+		getAttributeArray( _geometry.attributes.position ),
+		getAttributeArray( _geometry.attributes.normal ),
+		getAttributeArray( _geometry.attributes.uv )
+
+	);
+
+	// Texture coordinate convention of glTF differs from the apparent
+	// default of the MikkTSpace library; .w component must be flipped.
+
+	if ( negateSign ) {
+
+		for ( let i = 3; i < tangents.length; i += 4 ) {
+
+			tangents[ i ] *= -1;
+
+		}
+
+	}
+
+	//
+
+	_geometry.setAttribute( 'tangent', new BufferAttribute( tangents, 4 ) );
+
+	return geometry.copy( _geometry );
 
 }
 
 /**
-	 * @param  {Array<BufferGeometry>} geometries
-	 * @param  {Boolean} useGroups
-	 * @return {BufferGeometry}
-	 */
+ * @param  {Array<BufferGeometry>} geometries
+ * @param  {Boolean} useGroups
+ * @return {BufferGeometry}
+ */
 function mergeBufferGeometries( geometries, useGroups = false ) {
 
 	const isIndexed = geometries[ 0 ].index !== null;

src/math/MathUtils.js

@@ -233,6 +233,69 @@ function setQuaternionFromProperEuler( q, a, b, c, order ) {
 
 }
 
+function denormalize( value, array ) {
+
+	switch ( array.constructor ) {
+
+		case Float32Array:
+
+			return value;
+
+		case Uint16Array:
+
+			return value / 65535.0;
+
+		case Uint8Array:
+
+			return value / 255.0;
+
+		case Int16Array:
+
+			return Math.max( value / 32767.0, - 1.0 );
+
+		case Int8Array:
+
+			return Math.max( value / 127.0, - 1.0 );
+
+		default:
+
+			throw new Error( 'Invalid component type.' );
+
+	}
+
+}
+
+function normalize( value, array ) {
+
+	switch ( array.constructor ) {
+
+		case Float32Array:
+
+			return value;
+
+		case Uint16Array:
+
+			return Math.round( value * 65535.0 );
+
+		case Uint8Array:
+
+			return Math.round( value * 255.0 );
+
+		case Int16Array:
+
+			return Math.round( value * 32767.0 );
+
+		case Int8Array:
+
+			return Math.round( value * 127.0 );
+
+		default:
+
+			throw new Error( 'Invalid component type.' );
+
+	}
+
+}
 
 
 
@@ -259,4 +322,6 @@ export {
 	ceilPowerOfTwo,
 	floorPowerOfTwo,
 	setQuaternionFromProperEuler,
+	normalize,
+	denormalize,
 };