fix: apply opacity maps in preview

README.md

@@ -69,6 +69,7 @@ Access the app at `http://localhost:3000`
 >
 > Local 3D preview supports `model.gltf` folders by resolving dropped companion files such as `model.bin` and textures through local object URLs.
 > The preview also shows a small model stats helper with estimated draw calls, meshes, triangles, materials, and texture count.
+> Opacity helper textures can be named `opacity.png` for the whole model or `opacity_part-name.png` to target a mesh/material whose name contains `part-name`; alpha-channel PNGs are converted to alpha maps for the preview.
 
 ### Production (Coolify / Docker)
 

components/SceneViewer.tsx

@@ -4,8 +4,8 @@ import { Suspense, useEffect } from 'react'
 import { Canvas } from '@react-three/fiber'
 import { Stage, OrbitControls } from '@react-three/drei'
 import { useLoader } from '@react-three/fiber'
-import type { Material, Mesh, Object3D, Texture } from 'three'
-import { TextureLoader } from 'three'
+import { CanvasTexture, Mesh, TextureLoader } from 'three'
+import type { Material, Object3D, Texture } from 'three'
 import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader.js'
 
 export interface ModelStats {
@@ -21,6 +21,14 @@ interface OpacityMapEntry {
   url: string
 }
 
+interface AlphaMapMaterial extends Material {
+  alphaMap: Texture | null
+  transparent: boolean
+  alphaTest: number
+}
+
+const alphaMapTextureCache = new WeakMap<Texture, Texture>()
+
 function resolveAssetUrl(requestedUrl: string, assetUrls: Record<string, string>) {
   if (requestedUrl.startsWith('blob:') || requestedUrl.startsWith('data:')) {
     return requestedUrl
@@ -43,19 +51,84 @@ function getOpacityMapEntries(assetUrls: Record<string, string>) {
   }, [])
 }
 
+function normalizeMatchName(name: string) {
+  return name
+    .toLowerCase()
+    .normalize('NFD')
+    .replace(/[\u0300-\u036f]/g, '')
+    .replace(/[^a-z0-9]/g, '')
+}
+
 function getMaterialName(material: Material) {
-  return material.name.toLowerCase()
+  return normalizeMatchName(material.name)
 }
 
 function getObjectName(mesh: Mesh) {
-  return mesh.name.toLowerCase()
+  return normalizeMatchName(mesh.name)
+}
+
+function isMesh(object: Object3D): object is Mesh {
+  return object instanceof Mesh
+}
+
+function supportsAlphaMap(material: Material): material is AlphaMapMaterial {
+  return 'alphaMap' in material
+}
+
+function createAlphaMapTexture(texture: Texture) {
+  const cachedTexture = alphaMapTextureCache.get(texture)
+  if (cachedTexture) return cachedTexture
+
+  const image = texture.image as unknown
+  const isImageBitmap = typeof ImageBitmap !== 'undefined' && image instanceof ImageBitmap
+
+  if (!(image instanceof HTMLImageElement || image instanceof HTMLCanvasElement || isImageBitmap)) {
+    texture.flipY = false
+    alphaMapTextureCache.set(texture, texture)
+    return texture
+  }
+
+  const canvas = document.createElement('canvas')
+  canvas.width = image.width
+  canvas.height = image.height
+
+  const context = canvas.getContext('2d')
+  if (!context) {
+    texture.flipY = false
+    alphaMapTextureCache.set(texture, texture)
+    return texture
+  }
+
+  context.drawImage(image, 0, 0)
+
+  const imageData = context.getImageData(0, 0, canvas.width, canvas.height)
+  const pixels = imageData.data
+
+  for (let i = 0; i < pixels.length; i += 4) {
+    const alpha = pixels[i + 3]
+    const luminance = Math.round((pixels[i] * 0.2126) + (pixels[i + 1] * 0.7152) + (pixels[i + 2] * 0.0722))
+    const opacity = alpha < 255 ? alpha : luminance
+
+    pixels[i] = opacity
+    pixels[i + 1] = opacity
+    pixels[i + 2] = opacity
+    pixels[i + 3] = 255
+  }
+
+  context.putImageData(imageData, 0, 0)
+
+  const alphaTexture = new CanvasTexture(canvas)
+  alphaTexture.flipY = false
+  alphaTexture.needsUpdate = true
+  alphaMapTextureCache.set(texture, alphaTexture)
+
+  return alphaTexture
 }
 
 function applyAlphaMap(material: Material, texture: Texture) {
-  if (!('alphaMap' in material)) return
+  if (!supportsAlphaMap(material)) return
 
-  texture.flipY = false
-  material.alphaMap = texture
+  material.alphaMap = createAlphaMapTexture(texture)
   material.transparent = true
   material.alphaTest = 0.01
   material.needsUpdate = true
@@ -91,14 +164,13 @@ function getModelStats(scene: Object3D, assetUrls: Record<string, string>): Mode
   let triangles = 0
 
   scene.traverse((object) => {
-    const mesh = object as Mesh
-    if (!mesh.isMesh || !mesh.geometry || !mesh.material) return
+    if (!isMesh(object) || !object.geometry || !object.material) return
 
     meshes += 1
-    triangles += countGeometryTriangles(mesh)
-    drawCalls += estimateMeshDrawCalls(mesh)
+    triangles += countGeometryTriangles(object)
+    drawCalls += estimateMeshDrawCalls(object)
 
-    const meshMaterials = Array.isArray(mesh.material) ? mesh.material : [mesh.material]
+    const meshMaterials = Array.isArray(object.material) ? object.material : [object.material]
     meshMaterials.forEach((material) => materials.add(material))
   })
 
@@ -120,7 +192,10 @@ function pickOpacityMap(
   const objectName = getObjectName(mesh)
   const materialName = getMaterialName(material)
   const targetedIndex = entries.findIndex((entry) => (
-    entry.target && (objectName.includes(entry.target) || materialName.includes(entry.target))
+    entry.target && (
+      objectName.includes(normalizeMatchName(entry.target))
+      || materialName.includes(normalizeMatchName(entry.target))
+    )
   ))
 
   if (targetedIndex >= 0) return textures[targetedIndex]
@@ -154,12 +229,11 @@ function Model({
     if (opacityMapEntries.length === 0) return
 
     scene.traverse((object) => {
-      const mesh = object as Mesh
-      if (!mesh.isMesh || !mesh.material) return
+      if (!isMesh(object) || !object.material) return
 
-      const materials = Array.isArray(mesh.material) ? mesh.material : [mesh.material]
+      const materials = Array.isArray(object.material) ? object.material : [object.material]
       materials.forEach((material) => {
-        const opacityMap = pickOpacityMap(mesh, material, opacityMapEntries, opacityMaps)
+        const opacityMap = pickOpacityMap(object, material, opacityMapEntries, opacityMaps)
         if (opacityMap) applyAlphaMap(material, opacityMap)
       })
     })