BufferGeometryUtils: Fix mergeVertices() with normalized vertex attributes (#24577)

* BufferGeometryUtils: Fix mergeVertices() with normalized vertex attributes

* Clean up

examples/jsm/utils/BufferGeometryUtils.js

@@ -5,7 +5,6 @@ import {
 	InstancedBufferAttribute,
 	InterleavedBuffer,
 	InterleavedBufferAttribute,
-	MathUtils,
 	TriangleFanDrawMode,
 	TriangleStripDrawMode,
 	TrianglesDrawMode,
@@ -36,17 +35,16 @@ function computeMikkTSpaceTangents( geometry, MikkTSpace, negateSign = true ) {
 
 		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 );
+				dstArray[ j ++ ] = attribute.getX( i );
+				dstArray[ j ++ ] = attribute.getY( i );
 
 				if ( attribute.itemSize > 2 ) {
 
-					dstArray[ j ++ ] = MathUtils.denormalize( attribute.getZ( i ), srcArray );
+					dstArray[ j ++ ] = attribute.getZ( i );
 
 				}
 
@@ -573,22 +571,33 @@ function mergeVertices( geometry, tolerance = 1e-4 ) {
 
 	// attributes and new attribute arrays
 	const attributeNames = Object.keys( geometry.attributes );
-	const attrArrays = {};
-	const morphAttrsArrays = {};
+	const tmpAttributes = {};
+	const tmpMorphAttributes = {};
 	const newIndices = [];
 	const getters = [ 'getX', 'getY', 'getZ', 'getW' ];
+	const setters = [ 'setX', 'setY', 'setZ', 'setW' ];
 
-	// initialize the arrays
+	// Initialize the arrays, allocating space conservatively. Extra
+	// space will be trimmed in the last step.
 	for ( let i = 0, l = attributeNames.length; i < l; i ++ ) {
 
 		const name = attributeNames[ i ];
+		const attr = geometry.attributes[ name ];
 
-		attrArrays[ name ] = [];
+		tmpAttributes[ name ] = new BufferAttribute(
+			new attr.array.constructor( attr.count * attr.itemSize ),
+			attr.itemSize,
+			attr.normalized
+		);
 
 		const morphAttr = geometry.morphAttributes[ name ];
 		if ( morphAttr ) {
 
-			morphAttrsArrays[ name ] = new Array( morphAttr.length ).fill().map( () => [] );
+			tmpMorphAttributes[ name ] = new BufferAttribute(
+				new morphAttr.array.constructor( morphAttr.count * morphAttr.itemSize ),
+				morphAttr.itemSize,
+				morphAttr.normalized
+			);
 
 		}
 
@@ -626,26 +635,27 @@ function mergeVertices( geometry, tolerance = 1e-4 ) {
 
 		} else {
 
-			// copy data to the new index in the attribute arrays
+			// copy data to the new index in the temporary attributes
 			for ( let j = 0, l = attributeNames.length; j < l; j ++ ) {
 
 				const name = attributeNames[ j ];
 				const attribute = geometry.getAttribute( name );
 				const morphAttr = geometry.morphAttributes[ name ];
 				const itemSize = attribute.itemSize;
-				const newarray = attrArrays[ name ];
-				const newMorphArrays = morphAttrsArrays[ name ];
+				const newarray = tmpAttributes[ name ];
+				const newMorphArrays = tmpMorphAttributes[ name ];
 
 				for ( let k = 0; k < itemSize; k ++ ) {
 
 					const getterFunc = getters[ k ];
-					newarray.push( attribute[ getterFunc ]( index ) );
+					const setterFunc = setters[ k ];
+					newarray[ setterFunc ]( nextIndex, attribute[ getterFunc ]( index ) );
 
 					if ( morphAttr ) {
 
 						for ( let m = 0, ml = morphAttr.length; m < ml; m ++ ) {
 
-							newMorphArrays[ m ].push( morphAttr[ m ][ getterFunc ]( index ) );
+							newMorphArrays[ m ][ setterFunc ]( nextIndex, morphAttr[ m ][ getterFunc ]( index ) );
 
 						}
 
@@ -663,31 +673,29 @@ function mergeVertices( geometry, tolerance = 1e-4 ) {
 
 	}
 
-	// Generate typed arrays from new attribute arrays and update
-	// the attributeBuffers
+	// generate result BufferGeometry
 	const result = geometry.clone();
-	for ( let i = 0, l = attributeNames.length; i < l; i ++ ) {
-
-		const name = attributeNames[ i ];
-		const oldAttribute = geometry.getAttribute( name );
-
-		const buffer = new oldAttribute.array.constructor( attrArrays[ name ] );
-		const attribute = new BufferAttribute( buffer, oldAttribute.itemSize, oldAttribute.normalized );
+	for ( const name in geometry.attributes ) {
 
-		result.setAttribute( name, attribute );
+		const tmpAttribute = tmpAttributes[ name ];
 
-		// Update the attribute arrays
-		if ( name in morphAttrsArrays ) {
+		result.setAttribute( name, new BufferAttribute(
+			tmpAttribute.array.slice( 0, nextIndex * tmpAttribute.itemSize ),
+			tmpAttribute.itemSize,
+			tmpAttribute.normalized,
+		) );
 
-			for ( let j = 0; j < morphAttrsArrays[ name ].length; j ++ ) {
+		if ( ! ( name in tmpMorphAttributes ) ) continue;
 
-				const oldMorphAttribute = geometry.morphAttributes[ name ][ j ];
+		for ( let j = 0; j < tmpMorphAttributes[ name ].length; j ++ ) {
 
-				const buffer = new oldMorphAttribute.array.constructor( morphAttrsArrays[ name ][ j ] );
-				const morphAttribute = new BufferAttribute( buffer, oldMorphAttribute.itemSize, oldMorphAttribute.normalized );
-				result.morphAttributes[ name ][ j ] = morphAttribute;
+			const tmpMorphAttribute = tmpMorphAttributes[ name ][ j ];
 
-			}
+			result.morphAttributes[ name ][ j ] = new BufferAttribute(
+				tmpMorphAttribute.array.slice( 0, nextIndex * tmpMorphAttribute.itemSize ),
+				tmpMorphAttribute.itemSize,
+				tmpMorphAttribute.normalized,
+			);
 
 		}