feat: add model stats helper to viewer

components/SceneViewer.tsx

@@ -4,10 +4,18 @@ 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, Texture } from 'three'
+import type { Material, Mesh, Object3D, Texture } from 'three'
 import { TextureLoader } from 'three'
 import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader.js'
 
+export interface ModelStats {
+  drawCalls: number
+  materials: number
+  meshes: number
+  textures: number
+  triangles: number
+}
+
 interface OpacityMapEntry {
   target: string
   url: string
@@ -53,6 +61,56 @@ function applyAlphaMap(material: Material, texture: Texture) {
   material.needsUpdate = true
 }
 
+function countGeometryTriangles(mesh: Mesh) {
+  const geometry = mesh.geometry
+
+  if (geometry.index) return Math.floor(geometry.index.count / 3)
+
+  const position = geometry.getAttribute('position')
+  return position ? Math.floor(position.count / 3) : 0
+}
+
+function getMaterialCount(material: Material | Material[]) {
+  return Array.isArray(material) ? material.length : 1
+}
+
+function estimateMeshDrawCalls(mesh: Mesh) {
+  if (mesh.geometry.groups.length > 0) return mesh.geometry.groups.length
+
+  return getMaterialCount(mesh.material)
+}
+
+function getTextureCount(assetUrls: Record<string, string>) {
+  return Object.keys(assetUrls).filter((filename) => /\.(png|jpe?g|webp)$/i.test(filename)).length
+}
+
+function getModelStats(scene: Object3D, assetUrls: Record<string, string>): ModelStats {
+  const materials = new Set<Material>()
+  let drawCalls = 0
+  let meshes = 0
+  let triangles = 0
+
+  scene.traverse((object) => {
+    const mesh = object as Mesh
+    if (!mesh.isMesh || !mesh.geometry || !mesh.material) return
+
+    meshes += 1
+    triangles += countGeometryTriangles(mesh)
+    drawCalls += estimateMeshDrawCalls(mesh)
+
+    const meshMaterials = Array.isArray(mesh.material) ? mesh.material : [mesh.material]
+    meshMaterials.forEach((material) => materials.add(material))
+  })
+
+  return {
+    drawCalls,
+    materials: materials.size,
+    meshes,
+    textures: getTextureCount(assetUrls),
+    triangles,
+  }
+}
+
 function pickOpacityMap(
   mesh: Mesh,
   material: Material,
@@ -73,13 +131,25 @@ function pickOpacityMap(
   return entries.length === 1 ? textures[0] : undefined
 }
 
-function Model({ url, assetUrls }: { url: string; assetUrls: Record<string, string> }) {
+function Model({
+  url,
+  assetUrls,
+  onStatsReady,
+}: {
+  url: string
+  assetUrls: Record<string, string>
+  onStatsReady: (stats: ModelStats) => void
+}) {
   const { scene } = useLoader(GLTFLoader, url, (loader) => {
     loader.manager.setURLModifier((requestedUrl) => resolveAssetUrl(requestedUrl, assetUrls))
   })
   const opacityMapEntries = getOpacityMapEntries(assetUrls)
   const opacityMaps = useLoader(TextureLoader, opacityMapEntries.map((entry) => entry.url)) as Texture[]
 
+  useEffect(() => {
+    onStatsReady(getModelStats(scene, assetUrls))
+  }, [assetUrls, onStatsReady, scene])
+
   useEffect(() => {
     if (opacityMapEntries.length === 0) return
 
@@ -98,12 +168,20 @@ function Model({ url, assetUrls }: { url: string; assetUrls: Record<string, stri
   return <primitive object={scene} />
 }
 
-export default function SceneViewer({ url, assetUrls }: { url: string; assetUrls: Record<string, string> }) {
+export default function SceneViewer({
+  url,
+  assetUrls,
+  onStatsReady,
+}: {
+  url: string
+  assetUrls: Record<string, string>
+  onStatsReady: (stats: ModelStats) => void
+}) {
   return (
     <Canvas dpr={[1, 2]} camera={{ fov: 50 }}>
       <Suspense fallback={null}>
         <Stage environment="city" intensity={0.6} adjustCamera={1.2}>
-          <Model url={url} assetUrls={assetUrls} />
+          <Model url={url} assetUrls={assetUrls} onStatsReady={onStatsReady} />
         </Stage>
       </Suspense>
       <OrbitControls makeDefault autoRotate autoRotateSpeed={0.5} />