Detect glTF 2.0 and change forward to match Cesium's convention.

Apps/SampleData/models/DracoCompressed/CesiumMilkTruck.gltf

@@ -17,6 +17,24 @@
       "children": [
         3,
         1
+      ],
+      "matrix": [
+          0,
+          0,
+          1,
+          0,
+          0,
+          1,
+          0,
+          0,
+          -1,
+          0,
+          0,
+          0,
+          0,
+          0,
+          0,
+          1
       ]
     },
     {

Apps/Sandcastle/gallery/Physically-Based Materials.html

@@ -53,7 +53,7 @@
 viewer.scene.globe.depthTestAgainstTerrain = true;
 
 var position = new Cesium.Cartesian3(-1371108.6511167218, -5508684.080096612, 2901825.449865087);
-var heading = Cesium.Math.toRadians(90);
+var heading = Cesium.Math.toRadians(180);
 var pitch = Cesium.Math.toRadians(2);
 var roll = Cesium.Math.toRadians(-6);
 var hpr = new Cesium.HeadingPitchRoll(heading, pitch, roll);

Source/Scene/Model.js

@@ -579,6 +579,7 @@ define([
         this._ignoreCommands = defaultValue(options.ignoreCommands, false);
         this._requestType = options.requestType;
         this._upAxis = defaultValue(options.upAxis, Axis.Y);
+        this._forwardAxis = defaultValue(options.upAxis, Axis.Z);
 
         /**
          * @private
@@ -973,6 +974,25 @@ define([
             }
         },
 
+        /**
+         * Gets the model's forward axis.
+         * By default, glTF 2.0 models are z-forward according to the glTF spec, however older
+         * glTF (1.0, 0.8) models used x-forward.  Note that only Axis.X and Axis.Z are supported.
+         *
+         * @memberof Model.prototype
+         *
+         * @type {Number}
+         * @default Axis.Z
+         * @readonly
+         *
+         * @private
+         */
+        forwardAxis : {
+            get : function() {
+                return this._forwardAxis;
+            }
+        },
+
         /**
          * Gets the model's triangle count.
          *
@@ -1361,6 +1381,10 @@ define([
         } else if (model._upAxis === Axis.X) {
             BoundingSphere.transformWithoutScale(boundingSphere, Axis.X_UP_TO_Z_UP, boundingSphere);
         }
+        if (model._forwardAxis === Axis.Z) {
+            // glTF 2.0 has a Z-forward convention that must be adapted here to X-forward.
+            BoundingSphere.transformWithoutScale(boundingSphere, Axis.Z_UP_TO_X_UP, boundingSphere);
+        }
         return boundingSphere;
     }
 
@@ -4303,6 +4327,10 @@ define([
                     };
                     frameState.brdfLutGenerator.update(frameState);
                     updateVersion(this.gltf);
+                    if (defined(this.gltf.asset) && defined(this.gltf.asset.extras) &&
+                        this.gltf.asset.extras.gltf_pipeline_upgrade_10to20) {
+                            this._forwardAxis = Axis.X;
+                    }
                     ModelUtility.checkSupportedExtensions(this.extensionsRequired);
                     addPipelineExtras(this.gltf);
                     addDefaults(this.gltf);
@@ -4437,6 +4465,10 @@ define([
                 } else if (this._upAxis === Axis.X) {
                     Matrix4.multiplyTransformation(computedModelMatrix, Axis.X_UP_TO_Z_UP, computedModelMatrix);
                 }
+                if (this._forwardAxis === Axis.Z) {
+                    // glTF 2.0 has a Z-forward convention that must be adapted here to X-forward.
+                    Matrix4.multiplyTransformation(computedModelMatrix, Axis.Z_UP_TO_X_UP, computedModelMatrix);
+                }
             }
 
             // Update modelMatrix throughout the graph as needed

Source/ThirdParty/GltfPipeline/updateVersion.js

@@ -883,8 +883,12 @@ define([
         if (!defined(gltf.asset)) {
             gltf.asset = {};
         }
+        if (!defined(gltf.asset.extras)) {
+            gltf.asset.extras = {};
+        }
         var asset = gltf.asset;
         asset.version = '2.0';
+        asset.extras.gltf_pipeline_upgrade_10to20 = true;
         // material.instanceTechnique properties should be directly on the material. instanceTechnique is a gltf 0.8 property but is seen in some 1.0 models.
         updateInstanceTechniques(gltf);
         // animation.samplers now refers directly to accessors and animation.parameters should be removed

Specs/Data/Models/DracoCompression/CesiumMan/CesiumMan.gltf

@@ -18,13 +18,13 @@
         1
       ],
       "matrix": [
-        1,
         0,
         0,
+        1,
         0,
+        1,
         0,
         0,
-        -1,
         0,
         0,
         1,

Specs/Data/Models/DracoCompression/CesiumMilkTruck/CesiumMilkTruck.gltf

@@ -17,6 +17,24 @@
       "children": [
         3,
         1
+      ],
+      "matrix": [
+          0,
+          0,
+          1,
+          0,
+          0,
+          1,
+          0,
+          0,
+          -1,
+          0,
+          0,
+          0,
+          0,
+          0,
+          0,
+          1
       ]
     },
     {