Fix issue with glTF assets when transform have negative determinant

loaders/src/glTF/2.0/babylon.glTFLoader.ts

@@ -1370,7 +1370,8 @@ module BABYLON.GLTF2 {
                 let material = <PBRMaterial>this._babylonScene.getMaterialByName(id);
                 if (!material) {
                     material = new PBRMaterial(id, this._babylonScene);
-                    material.sideOrientation = Material.CounterClockWiseSideOrientation;
+                    material.transparencyMode = PBRMaterial.PBRMATERIAL_OPAQUE;
+                    material.sideOrientation = Material.ClockWiseSideOrientation;
                     material.metallic = 1;
                     material.roughness = 1;
                 }
@@ -1439,7 +1440,7 @@ module BABYLON.GLTF2 {
 
         public _createPbrMaterial(material: IGLTFMaterial): void {
             const babylonMaterial = new PBRMaterial(material.name || "mat" + material.index, this._babylonScene);
-            babylonMaterial.sideOrientation = Material.CounterClockWiseSideOrientation;
+            babylonMaterial.sideOrientation = Material.ClockWiseSideOrientation;
             material.babylonMaterial = babylonMaterial;
         }
 

src/Mesh/babylon.abstractMesh.ts

@@ -803,6 +803,17 @@
             return super.getWorldMatrix();
         }
 
+        /**
+         * Returns the latest update of the World matrix determinant.
+         */
+        protected _getWorldMatrixDeterminant(): number {
+            if (this._masterMesh) {
+                return this._masterMesh._getWorldMatrixDeterminant();
+            }
+
+            return super._getWorldMatrixDeterminant();
+        }
+
         // ================================== Point of View Movement =================================
         /**
          * Perform relative position change from the point of view of behind the front of the mesh.

src/Mesh/babylon.mesh.ts

@@ -1304,7 +1304,7 @@
                 return this;
             }
 
-            this._effectiveMaterial = material
+            this._effectiveMaterial = material;
 
             if (this._effectiveMaterial.storeEffectOnSubMeshes) {
                 if (!this._effectiveMaterial.isReadyForSubMesh(this, subMesh, hardwareInstancedRendering)) {
@@ -1338,7 +1338,15 @@
                 return this;
             }
 
-            var reverse = this._effectiveMaterial._preBind(effect, this.overrideMaterialSideOrientation);
+            var sideOrientation = this.overrideMaterialSideOrientation;
+            if (sideOrientation == null) {
+                sideOrientation = this._effectiveMaterial.sideOrientation;
+                if (this._getWorldMatrixDeterminant() < 0) {
+                    sideOrientation = (sideOrientation === Material.ClockWiseSideOrientation ? Material.CounterClockWiseSideOrientation : Material.ClockWiseSideOrientation);
+                }
+            }
+
+            var reverse = this._effectiveMaterial._preBind(effect, sideOrientation);
 
             if (this._effectiveMaterial.forceDepthWrite) {
                 engine.setDepthWrite(true);

src/Mesh/babylon.transformNode.ts

@@ -35,6 +35,7 @@ module BABYLON {
         public _poseMatrix: Matrix;
         private _localWorld = Matrix.Zero();
         public _worldMatrix = Matrix.Zero();
+        public _worldMatrixDeterminant = 0;
         private _absolutePosition = Vector3.Zero();
         private _pivotMatrix = Matrix.Identity();
         private _pivotMatrixInverse: Matrix;
@@ -114,6 +115,16 @@ module BABYLON {
         }
 
         /**
+         * Returns the latest update of the World matrix determinant.
+         */
+        protected _getWorldMatrixDeterminant(): number {
+            if (this._currentRenderId !== this.getScene().getRenderId()) {
+                this._worldMatrixDeterminant = this.computeWorldMatrix().determinant();
+            }
+            return this._worldMatrixDeterminant;
+        }
+
+        /**
          * Returns directly the latest state of the mesh World matrix. 
          * A Matrix is returned.    
          */