gltfio: various improvements to skinning normalization.

- Allow JavaScript and Java / Kotlin clients to configure this setting.
- Opt in by default (this was disabled in #2621)
- Optimize large assets like Bistro by iterating through prims only when
  the asset actually has skins.

Fixes #2714.

android/filament-utils-android/src/main/java/com/google/android/filament/utils/ModelViewer.kt

@@ -70,6 +70,9 @@ class ModelViewer(val engine: Engine) : android.view.View.OnTouchListener {
     val progress
         get() = resourceLoader.asyncGetLoadProgress()
 
+    var normalizeSkinningWeights = true
+    var recomputeBoundingBoxes = false
+
     val scene: Scene
     val view: View
     val camera: Camera
@@ -101,7 +104,7 @@ class ModelViewer(val engine: Engine) : android.view.View.OnTouchListener {
         view.camera = camera
 
         assetLoader = AssetLoader(engine, MaterialProvider(engine), EntityManager.get())
-        resourceLoader = ResourceLoader(engine, false, false)
+        resourceLoader = ResourceLoader(engine, normalizeSkinningWeights, recomputeBoundingBoxes)
 
         // Always add a direct light source since it is required for shadowing.
         // We highly recommend adding an indirect light as well.

libs/gltfio/src/ResourceLoader.cpp

@@ -296,7 +296,7 @@ bool ResourceLoader::loadResources(FFilamentAsset* asset, bool async) {
     }
     asset->mResourcesLoaded = true;
     mPool->addAsset(asset);
-    auto gltf = (cgltf_data*) asset->mSourceAsset;
+    const cgltf_data* gltf = asset->mSourceAsset;
     cgltf_options options {};
 
     // For emscripten and Android builds we have a custom implementation of cgltf_load_buffers which
@@ -361,7 +361,7 @@ bool ResourceLoader::loadResources(FFilamentAsset* asset, bool async) {
     #else
 
     // Read data from the file system and base64 URIs.
-    cgltf_result result = cgltf_load_buffers(&options, gltf, pImpl->mGltfPath.c_str());
+    cgltf_result result = cgltf_load_buffers(&options, (cgltf_data*) gltf, pImpl->mGltfPath.c_str());
     if (result != cgltf_result_success) {
         slog.e << "Unable to load resources." << io::endl;
         return false;
@@ -371,7 +371,7 @@ bool ResourceLoader::loadResources(FFilamentAsset* asset, bool async) {
     SYSTRACE_NAME_END();
 
     #ifndef NDEBUG
-    if (cgltf_validate(gltf) != cgltf_result_success) {
+    if (cgltf_validate((cgltf_data*) gltf) != cgltf_result_success) {
         slog.e << "Failed cgltf validation." << io::endl;
         return false;
     }
@@ -381,13 +381,19 @@ bool ResourceLoader::loadResources(FFilamentAsset* asset, bool async) {
     // tangent generation.
     decodeDracoMeshes(asset);
 
-    // To be robust against the glTF conformance suite, we optionally ensure that skinning weights
-    // sum to 1.0 at every vertex. Note that if the same weights buffer is shared in multiple
-    // places, this will needlessly repeat the work. In the future we would like to remove this
-    // feature, and instead simply require correct models. See also:
-    // https://github.com/KhronosGroup/glTF-Sample-Models/issues/215
-    if (pImpl->mNormalizeSkinningWeights) {
-        normalizeSkinningWeights(asset);
+    // Normalize skinning weights, then "import" each skin into the asset by building a mapping of
+    // skins to their affected entities.
+    if (gltf->skins_count > 0) {
+        if (pImpl->mNormalizeSkinningWeights) {
+            normalizeSkinningWeights(asset);
+        }
+        if (asset->mInstances.empty()) {
+            importSkins(gltf, asset->mNodeMap, asset->mSkins);
+        } else {
+            for (FFilamentInstance* instance : asset->mInstances) {
+                importSkins(gltf, instance->nodeMap, instance->skins);
+            }
+        }
     }
 
     if (pImpl->mRecomputeBoundingBoxes) {
@@ -425,16 +431,6 @@ bool ResourceLoader::loadResources(FFilamentAsset* asset, bool async) {
         slot.indexBuffer->setBuffer(engine, std::move(bd));
     }
 
-    // For each skin, build a list of renderables that it affects.
-    const cgltf_data* const_gltf = gltf;
-    if (asset->mInstances.empty()) {
-        importSkins(const_gltf, asset->mNodeMap, asset->mSkins);
-    } else {
-        for (FFilamentInstance* instance : asset->mInstances) {
-            importSkins(const_gltf, instance->nodeMap, instance->skins);
-        }
-    }
-
     // Apply sparse data modifications to base arrays, then upload the result.
     applySparseData(asset);
 

samples/gltf_viewer.cpp

@@ -620,6 +620,7 @@ int main(int argc, char** argv) {
         configuration.engine = app.engine;
         configuration.gltfPath = gltfPath.c_str();
         configuration.recomputeBoundingBoxes = app.recomputeAabb;
+        configuration.normalizeSkinningWeights = true;
         if (!app.resourceLoader) {
             app.resourceLoader = new gltfio::ResourceLoader(configuration);
         }

web/filament-js/extensions.js

@@ -396,12 +396,20 @@ Filament.loadClassExtensions = function() {
     //
     // The optional asyncInterval argument allows clients to control how decoding is amortized
     // over time. It represents the number of milliseconds between each texture decoding task.
+    //
+    // The optional config argument is an object with boolean fields `normalizeSkinningWeights` and
+    // `recomputeBoundingBoxes`.
     Filament.gltfio$FilamentAsset.prototype.loadResources = function(onDone, onFetched, basePath,
-            asyncInterval) {
+            asyncInterval, config) {
         const asset = this;
         const engine = this.getEngine();
         const names = this.getResourceUris();
         const interval = asyncInterval || 30;
+        const defaults = {
+            normalizeSkinningWeights: true,
+            recomputeBoundingBoxes: false
+        };
+        config = Object.assign(defaults, config || {});
 
         basePath = basePath || document.location;
         onFetched = onFetched || ((name) => {});
@@ -420,7 +428,9 @@ Filament.loadClassExtensions = function() {
         }
 
         // Construct a resource loader and start decoding after all textures are fetched.
-        const resourceLoader = new Filament.gltfio$ResourceLoader(engine, false, false);
+        const resourceLoader = new Filament.gltfio$ResourceLoader(engine,
+                config.normalizeSkinningWeights,
+                config.recomputeBoundingBoxes);
         const onComplete = () => {
             resourceLoader.asyncBeginLoad(asset);
 

web/filament-js/filament.d.ts

@@ -465,7 +465,7 @@ export class gltfio$AssetLoader {
 
 export class gltfio$FilamentAsset {
     public loadResources(onDone: () => void|null, onFetched: (s: string) => void|null,
-            basePath: string|null, asyncInterval: number|null): void;
+            basePath: string|null, asyncInterval: number|null, options?: object): void;
     public getEntities(): Entity[];
     public getEntitiesByName(name: string): Entity[];
     public getEntityByName(name: string): Entity;