Merge pull request #1553 from pixiv/improve-combinemorphs

Improve performance of combineMorphs

Author: 0b5vr

packages/three-vrm/src/VRMUtils/combineMorphs.ts

@@ -21,9 +21,17 @@ function collectMeshes(scene: THREE.Group): Set<THREE.Mesh> {
 
 function combineMorph(
   positionAttributes: (THREE.BufferAttribute | THREE.InterleavedBufferAttribute)[],
-  binds: Iterable<VRMExpressionMorphTargetBind>,
+  binds: Set<VRMExpressionMorphTargetBind>,
   morphTargetsRelative: boolean,
-): THREE.BufferAttribute {
+): THREE.BufferAttribute | THREE.InterleavedBufferAttribute {
+  // if there is only one morph target and the weight is 1.0, we can use the original as-is
+  if (binds.size === 1) {
+    const bind = binds.values().next().value!;
+    if (bind.weight === 1.0) {
+      return positionAttributes[bind.index];
+    }
+  }
+
   const newArray = new Float32Array(positionAttributes[0].count * 3);
   let weightSum = 0.0;
 
@@ -108,14 +116,18 @@ export function combineMorphs(vrm: VRMCore): void {
       continue;
     }
 
+    // prevent cloning morph attributes
+    const originalMorphAttributes = mesh.geometry.morphAttributes;
+    mesh.geometry.morphAttributes = {};
+
     const geometry = mesh.geometry.clone();
     mesh.geometry = geometry;
     const morphTargetsRelative = geometry.morphTargetsRelative;
 
-    const hasPMorph = geometry.morphAttributes.position != null;
-    const hasNMorph = geometry.morphAttributes.normal != null;
+    const hasPMorph = originalMorphAttributes.position != null;
+    const hasNMorph = originalMorphAttributes.normal != null;
 
-    const morphAttributes: typeof geometry.morphAttributes = {};
+    const morphAttributes: typeof originalMorphAttributes = {};
     const morphTargetDictionary: typeof mesh.morphTargetDictionary = {};
     const morphTargetInfluences: typeof mesh.morphTargetInfluences = [];
 
@@ -130,10 +142,10 @@ export function combineMorphs(vrm: VRMCore): void {
       let i = 0;
       for (const [name, bindSet] of nameBindSetMap) {
         if (hasPMorph) {
-          morphAttributes.position[i] = combineMorph(geometry.morphAttributes.position, bindSet, morphTargetsRelative);
+          morphAttributes.position[i] = combineMorph(originalMorphAttributes.position, bindSet, morphTargetsRelative);
         }
         if (hasNMorph) {
-          morphAttributes.normal[i] = combineMorph(geometry.morphAttributes.normal, bindSet, morphTargetsRelative);
+          morphAttributes.normal[i] = combineMorph(originalMorphAttributes.normal, bindSet, morphTargetsRelative);
         }
 
         expressionMap?.[name].addBind(