add unit test for reading instanceFeatures test files

tests/SharpGLTF.Cesium.Tests/ExtInstanceFeaturesTests.cs

@@ -2,6 +2,7 @@
 using SharpGLTF.Scenes;
 using SharpGLTF.Transforms;
 using SharpGLTF.Validation;
+using System.IO;
 using System.Numerics;
 using System.Text.Json.Nodes;
 
@@ -16,6 +17,35 @@ namespace SharpGLTF.Schema2.Tiles3D
             Tiles3DExtensions.RegisterExtensions();
         }
 
+        // Test files are from https://github.com/CesiumGS/3d-tiles-validator/tree/main/specs/data/gltfExtensions/instanceFeatures
+
+        [Test(Description = "Reads glTF's with Cesium EXT_Instance_Features")]
+        public void ReadExtInstanceFeatures()
+        {
+            var gltffiles = Directory.GetFiles("./testfixtures/instanceFeatures", "*.gltf");
+
+            foreach (var file in gltffiles)
+            {
+                var fileName = Path.GetFileName(file);
+
+                if (fileName.StartsWith("InstanceFeatures"))
+                {
+                    // we can expect an error loading this file
+                    Assert.That(() => ModelRoot.Load(file), Throws.Exception);
+                }
+                else
+                {
+                    var model = ModelRoot.Load(file);
+                    var instanceFeaturesExtension = model.LogicalNodes[0].GetExtension<MeshExtInstanceFeatures>();
+                    Assert.That(instanceFeaturesExtension.FeatureIds, Is.Not.Null);
+                    Assert.That(instanceFeaturesExtension.FeatureIds, Has.Count.GreaterThanOrEqualTo(1));
+                    var ctx = new ValidationResult(model, ValidationMode.Strict, true);
+                    model.ValidateContent(ctx.GetContext());
+                }
+            }
+        }
+
+
         [Test(Description = "Creates a gpu_instancing glTF from a tree with Cesium EXT_Instance_Features")]
         // Sample model structure is from https://github.com/CesiumGS/glTF/tree/3d-tiles-next/extensions/2.0/Vendor/EXT_instance_features
         public void AddExtGpuInstanceFeatures()

tests/SharpGLTF.Cesium.Tests/ExtMeshFeaturesTests.cs

@@ -23,6 +23,7 @@ namespace SharpGLTF.Schema2.Tiles3D
             Tiles3DExtensions.RegisterExtensions();
         }
 
+        // Test files are from https://github.com/CesiumGS/3d-tiles-validator/tree/main/specs/data/gltfExtensions/meshFeatures
         [Test(Description = "Reads glTF's with Cesium EXT_Mesh_Features")]
         public void ReadExtMeshFeatures()
         {
@@ -42,14 +43,11 @@ namespace SharpGLTF.Schema2.Tiles3D
                 else
                 {
                     var model = ModelRoot.Load(file);
-                    var cesiumExtMeshFeaturesExtension = model.LogicalMeshes[0].Primitives[0].GetExtension<MeshExtMeshFeatures>();
-                    if (cesiumExtMeshFeaturesExtension != null)
-                    {
-                        Assert.That(cesiumExtMeshFeaturesExtension.FeatureIds, Is.Not.Null);
-                        Assert.That(cesiumExtMeshFeaturesExtension.FeatureIds, Has.Count.GreaterThanOrEqualTo(1));
-                        var ctx = new ValidationResult(model, ValidationMode.Strict, true);
-                        model.ValidateContent(ctx.GetContext());
-                    }
+                    var meshFeaturesExtension = model.LogicalMeshes[0].Primitives[0].GetExtension<MeshExtMeshFeatures>();
+                    Assert.That(meshFeaturesExtension.FeatureIds, Is.Not.Null);
+                    Assert.That(meshFeaturesExtension.FeatureIds, Has.Count.GreaterThanOrEqualTo(1));
+                    var ctx = new ValidationResult(model, ValidationMode.Strict, true);
+                    model.ValidateContent(ctx.GetContext());
                 }
             }
         }
@@ -82,11 +80,11 @@ namespace SharpGLTF.Schema2.Tiles3D
             model.LogicalMeshes[0].Primitives[0].AddMeshFeatureIds(featureIdAttribute);
 
             // Validate the FeatureIds
-            var cesiumExtMeshFeaturesExtension = (MeshExtMeshFeatures)model.LogicalMeshes[0].Primitives[0].Extensions.FirstOrDefault();
-            Assert.That(cesiumExtMeshFeaturesExtension.FeatureIds, Is.Not.Null);
+            var meshFeaturesExtension = (MeshExtMeshFeatures)model.LogicalMeshes[0].Primitives[0].Extensions.FirstOrDefault();
+            Assert.That(meshFeaturesExtension.FeatureIds, Is.Not.Null);
 
             // Check there should be a custom vertex attribute with name _FEATURE_ID_{attribute}
-            var attribute = cesiumExtMeshFeaturesExtension.FeatureIds[0].Attribute;
+            var attribute = meshFeaturesExtension.FeatureIds[0].Attribute;
             Assert.That(attribute == 0);
             var primitive = model.LogicalMeshes[0].Primitives[0];
             var featureIdVertexAccessor = primitive.GetVertexAccessor($"_FEATURE_ID_{attribute}");
@@ -143,10 +141,10 @@ namespace SharpGLTF.Schema2.Tiles3D
             var primitive = model.LogicalMeshes[0].Primitives[0];
             primitive.AddMeshFeatureIds(featureId);
 
-            var cesiumExtMeshFeaturesExtension = (MeshExtMeshFeatures)primitive.Extensions.FirstOrDefault();
-            Assert.That(cesiumExtMeshFeaturesExtension.FeatureIds, Is.Not.Null);
+            var meshFeaturesExtension = (MeshExtMeshFeatures)primitive.Extensions.FirstOrDefault();
+            Assert.That(meshFeaturesExtension.FeatureIds, Is.Not.Null);
 
-            var firstFeatureId = cesiumExtMeshFeaturesExtension.FeatureIds[0];
+            var firstFeatureId = meshFeaturesExtension.FeatureIds[0];
             var texture = firstFeatureId.GetTexture();
             var texCoord = texture.TextureCoordinate;
             var textureIdVertexAccessor = primitive.GetVertexAccessor($"TEXCOORD_{texCoord}");

tests/SharpGLTF.Cesium.Tests/SharpGLTF.Cesium.Tests.csproj

@@ -30,7 +30,7 @@
 	<Folder Include="testfixtures\meshFeatures\" />
 	<Folder Include="testfixtures\instanceFeatures\" />
     <Folder Include="testfixtures\structuralMetadata\" />
-	<None Update="testfixtures\meshFeatures\**\*" CopyToOutputDirectory="PreserveNewest" />
+	<None Update="testfixtures\**\*" CopyToOutputDirectory="PreserveNewest" />
 
   </ItemGroup>
 

tests/SharpGLTF.Cesium.Tests/testfixtures/instanceFeatures/InstanceFeaturesFeatureIdAttributeInvalidValue.gltf

@@ -0,0 +1,179 @@
+{
+  "extensions" : {
+    "EXT_structural_metadata" : {
+      "schema" : {
+        "id": "GpuInstancesMetadataSchema",
+        "classes" : {
+          "exampleMetadataClass" : {
+            "name" : "Example metadata class",
+            "description" : "An example metadata class",
+            "properties" : {
+              "example_STRING" : {
+                "name" : "Example STRING property",
+                "description" : "An example property, with component type STRING",
+                "type" : "STRING"
+              }
+            }
+          }
+        }
+      },
+      "propertyTables" : [ {
+        "name" : "Example property table",
+        "class" : "exampleMetadataClass",
+        "count" : 10,
+        "properties" : {
+          "example_STRING" : {
+            "values" : 7,
+            "stringOffsets" : 8
+          }
+        }
+      } ]
+    }
+  },
+  "extensionsUsed" : [ "EXT_structural_metadata", "EXT_mesh_gpu_instancing", "EXT_instance_features" ],
+  "accessors" : [ {
+    "bufferView" : 0,
+    "byteOffset" : 0,
+    "componentType" : 5125,
+    "count" : 36,
+    "type" : "SCALAR",
+    "max" : [ 23 ],
+    "min" : [ 0 ]
+  }, {
+    "bufferView" : 1,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 24,
+    "type" : "VEC3",
+    "max" : [ 1.0, 1.0, 1.0 ],
+    "min" : [ 0.0, 0.0, 0.0 ]
+  }, {
+    "bufferView" : 2,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 24,
+    "type" : "VEC3",
+    "max" : [ 1.0, 1.0, 1.0 ],
+    "min" : [ -1.0, -1.0, -1.0 ]
+  }, {
+    "bufferView" : 3,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC3",
+    "max" : [ 10.0, 10.0, 10.0 ],
+    "min" : [ 0.0, 0.0, 0.0 ]
+  }, {
+    "bufferView" : 4,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC4",
+    "max" : [ 0.733, 0.462, 0.191, 1.0 ],
+    "min" : [ 0.0, 0.0, 0.0, 0.462 ]
+  }, {
+    "bufferView" : 5,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC3",
+    "max" : [ 2.0, 2.0, 2.0 ],
+    "min" : [ 1.0, 1.0, 1.0 ]
+  }, {
+    "bufferView" : 6,
+    "byteOffset" : 0,
+    "componentType" : 5123,
+    "count" : 10,
+    "type" : "SCALAR",
+    "max" : [ 9 ],
+    "min" : [ 0 ]
+  } ],
+  "asset" : {
+    "generator" : "JglTF from https://github.com/javagl/JglTF",
+    "version" : "2.0"
+  },
+  "buffers" : [ {
+    "uri" : "data:application/gltf-buffer;base64,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",
+    "byteLength" : 720
+  }, {
+    "uri" : "data:application/gltf-buffer;base64,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",
+    "byteLength" : 420
+  }, {
+    "uri" : "data:application/gltf-buffer;base64,emVyb29uZXR3b3RocmVlZm91cmZpdmVzaXhzZXZlbmVpZ2h0bmluZQAAAAAEAAAABwAAAAoAAAAPAAAAEwAAABcAAAAaAAAAHwAAACQAAAAoAAAA",
+    "byteLength" : 84
+  } ],
+  "bufferViews" : [ {
+    "buffer" : 0,
+    "byteOffset" : 0,
+    "byteLength" : 144,
+    "target" : 34963
+  }, {
+    "buffer" : 0,
+    "byteOffset" : 144,
+    "byteLength" : 288,
+    "target" : 34962
+  }, {
+    "buffer" : 0,
+    "byteOffset" : 432,
+    "byteLength" : 288,
+    "target" : 34962
+  }, {
+    "buffer" : 1,
+    "byteOffset" : 0,
+    "byteLength" : 120
+  }, {
+    "buffer" : 1,
+    "byteOffset" : 120,
+    "byteLength" : 160
+  }, {
+    "buffer" : 1,
+    "byteOffset" : 280,
+    "byteLength" : 120
+  }, {
+    "buffer" : 1,
+    "byteOffset" : 400,
+    "byteLength" : 20
+  }, {
+    "buffer" : 2,
+    "byteOffset" : 0,
+    "byteLength" : 40
+  }, {
+    "buffer" : 2,
+    "byteOffset" : 40,
+    "byteLength" : 44
+  } ],
+  "meshes" : [ {
+    "primitives" : [ {
+      "attributes" : {
+        "POSITION" : 1,
+        "NORMAL" : 2
+      },
+      "indices" : 0,
+      "mode" : 4
+    } ]
+  } ],
+  "nodes" : [ {
+    "extensions" : {
+      "EXT_mesh_gpu_instancing" : {
+        "attributes" : {
+          "TRANSLATION" : 3,
+          "ROTATION" : 4,
+          "SCALE" : 5,
+          "_FEATURE_ID_0" : 6
+        }
+      },
+      "EXT_instance_features" : {
+        "featureIds" : [ {
+          "featureCount" : 10,
+          "attribute" : 12345,
+          "propertyTable" : 0
+        } ]
+      }
+    },
+    "mesh" : 0
+  } ],
+  "scene" : 0,
+  "scenes" : [ {
+    "nodes" : [ 0 ]
+  } ]
+}

tests/SharpGLTF.Cesium.Tests/testfixtures/instanceFeatures/InstanceFeaturesWithoutMeshGpuInstancing.gltf

@@ -0,0 +1,171 @@
+{
+  "extensions" : {
+    "EXT_structural_metadata" : {
+      "schema" : {
+        "id": "GpuInstancesMetadataSchema",
+        "classes" : {
+          "exampleMetadataClass" : {
+            "name" : "Example metadata class",
+            "description" : "An example metadata class",
+            "properties" : {
+              "example_STRING" : {
+                "name" : "Example STRING property",
+                "description" : "An example property, with component type STRING",
+                "type" : "STRING"
+              }
+            }
+          }
+        }
+      },
+      "propertyTables" : [ {
+        "name" : "Example property table",
+        "class" : "exampleMetadataClass",
+        "count" : 10,
+        "properties" : {
+          "example_STRING" : {
+            "values" : 7,
+            "stringOffsets" : 8
+          }
+        }
+      } ]
+    }
+  },
+  "extensionsUsed" : [ "EXT_structural_metadata", "EXT_mesh_gpu_instancing", "EXT_instance_features" ],
+  "accessors" : [ {
+    "bufferView" : 0,
+    "byteOffset" : 0,
+    "componentType" : 5125,
+    "count" : 36,
+    "type" : "SCALAR",
+    "max" : [ 23 ],
+    "min" : [ 0 ]
+  }, {
+    "bufferView" : 1,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 24,
+    "type" : "VEC3",
+    "max" : [ 1.0, 1.0, 1.0 ],
+    "min" : [ 0.0, 0.0, 0.0 ]
+  }, {
+    "bufferView" : 2,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 24,
+    "type" : "VEC3",
+    "max" : [ 1.0, 1.0, 1.0 ],
+    "min" : [ -1.0, -1.0, -1.0 ]
+  }, {
+    "bufferView" : 3,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC3",
+    "max" : [ 10.0, 10.0, 10.0 ],
+    "min" : [ 0.0, 0.0, 0.0 ]
+  }, {
+    "bufferView" : 4,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC4",
+    "max" : [ 0.733, 0.462, 0.191, 1.0 ],
+    "min" : [ 0.0, 0.0, 0.0, 0.462 ]
+  }, {
+    "bufferView" : 5,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC3",
+    "max" : [ 2.0, 2.0, 2.0 ],
+    "min" : [ 1.0, 1.0, 1.0 ]
+  }, {
+    "bufferView" : 6,
+    "byteOffset" : 0,
+    "componentType" : 5123,
+    "count" : 10,
+    "type" : "SCALAR",
+    "max" : [ 9 ],
+    "min" : [ 0 ]
+  } ],
+  "asset" : {
+    "generator" : "JglTF from https://github.com/javagl/JglTF",
+    "version" : "2.0"
+  },
+  "buffers" : [ {
+    "uri" : "data:application/gltf-buffer;base64,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",
+    "byteLength" : 720
+  }, {
+    "uri" : "data:application/gltf-buffer;base64,AAAAAAAAAAAAAAAA5DiOP+Q4jj/kOI4/5DgOQOQ4DkDkOA5AVlVVQFZVVUBWVVVA5DiOQOQ4jkDkOI5AHcexQB3HsUAdx7FAVlXVQFZV1UBWVdVAjuP4QI7j+ECO4/hA5DgOQeQ4DkHkOA5BAAAgQQAAIEEAACBBAAAAAAAAAAAAAAAAAACAP92ZzD0Q9YA9B0HVPHcffj/QGUs+AAMAPrywUz3rhHg/HXaWPuWqPT4f05w9Y0VvP3UqxT6+ing+IIHNPZiDYj+d+vA+w+KXPqEr+z1ub1I/DaEMP/RFsT6bkxI+REU/P9m0Hj+hD8g+H2slPgpNKT/WdC4/P+rbPqHVNT462RA/46U7P0SL7D6BlUM+RIvsPgAAgD8AAIA/AACAP+Q4jj/kOI4/5DiOP8dxnD/HcZw/x3GcP6uqqj+rqqo/q6qqP47juD+O47g/juO4P3Icxz9yHMc/chzHP1ZV1T9WVdU/VlXVPzmO4z85juM/OY7jPxzH8T8cx/E/HMfxPwAAAEAAAABAAAAAQAkACAAHAAYABQAEAAMAAgABAAAA",
+    "byteLength" : 420
+  }, {
+    "uri" : "data:application/gltf-buffer;base64,emVyb29uZXR3b3RocmVlZm91cmZpdmVzaXhzZXZlbmVpZ2h0bmluZQAAAAAEAAAABwAAAAoAAAAPAAAAEwAAABcAAAAaAAAAHwAAACQAAAAoAAAA",
+    "byteLength" : 84
+  } ],
+  "bufferViews" : [ {
+    "buffer" : 0,
+    "byteOffset" : 0,
+    "byteLength" : 144,
+    "target" : 34963
+  }, {
+    "buffer" : 0,
+    "byteOffset" : 144,
+    "byteLength" : 288,
+    "target" : 34962
+  }, {
+    "buffer" : 0,
+    "byteOffset" : 432,
+    "byteLength" : 288,
+    "target" : 34962
+  }, {
+    "buffer" : 1,
+    "byteOffset" : 0,
+    "byteLength" : 120
+  }, {
+    "buffer" : 1,
+    "byteOffset" : 120,
+    "byteLength" : 160
+  }, {
+    "buffer" : 1,
+    "byteOffset" : 280,
+    "byteLength" : 120
+  }, {
+    "buffer" : 1,
+    "byteOffset" : 400,
+    "byteLength" : 20
+  }, {
+    "buffer" : 2,
+    "byteOffset" : 0,
+    "byteLength" : 40
+  }, {
+    "buffer" : 2,
+    "byteOffset" : 40,
+    "byteLength" : 44
+  } ],
+  "meshes" : [ {
+    "primitives" : [ {
+      "attributes" : {
+        "POSITION" : 1,
+        "NORMAL" : 2
+      },
+      "indices" : 0,
+      "mode" : 4
+    } ]
+  } ],
+  "nodes" : [ {
+    "extensions" : {
+      "EXT_instance_features" : {
+        "featureIds" : [ {
+          "featureCount" : 10,
+          "attribute" : 0,
+          "propertyTable" : 0
+        } ]
+      }
+    },
+    "mesh" : 0
+  } ],
+  "scene" : 0,
+  "scenes" : [ {
+    "nodes" : [ 0 ]
+  } ]
+}

tests/SharpGLTF.Cesium.Tests/testfixtures/instanceFeatures/ValidInstanceFeatures.gltf

@@ -0,0 +1,179 @@
+{
+  "extensions" : {
+    "EXT_structural_metadata" : {
+      "schema" : {
+        "id": "GpuInstancesMetadataSchema",
+        "classes" : {
+          "exampleMetadataClass" : {
+            "name" : "Example metadata class",
+            "description" : "An example metadata class",
+            "properties" : {
+              "example_STRING" : {
+                "name" : "Example STRING property",
+                "description" : "An example property, with component type STRING",
+                "type" : "STRING"
+              }
+            }
+          }
+        }
+      },
+      "propertyTables" : [ {
+        "name" : "Example property table",
+        "class" : "exampleMetadataClass",
+        "count" : 10,
+        "properties" : {
+          "example_STRING" : {
+            "values" : 7,
+            "stringOffsets" : 8
+          }
+        }
+      } ]
+    }
+  },
+  "extensionsUsed" : [ "EXT_structural_metadata", "EXT_mesh_gpu_instancing", "EXT_instance_features" ],
+  "accessors" : [ {
+    "bufferView" : 0,
+    "byteOffset" : 0,
+    "componentType" : 5125,
+    "count" : 36,
+    "type" : "SCALAR",
+    "max" : [ 23 ],
+    "min" : [ 0 ]
+  }, {
+    "bufferView" : 1,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 24,
+    "type" : "VEC3",
+    "max" : [ 1.0, 1.0, 1.0 ],
+    "min" : [ 0.0, 0.0, 0.0 ]
+  }, {
+    "bufferView" : 2,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 24,
+    "type" : "VEC3",
+    "max" : [ 1.0, 1.0, 1.0 ],
+    "min" : [ -1.0, -1.0, -1.0 ]
+  }, {
+    "bufferView" : 3,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC3",
+    "max" : [ 10.0, 10.0, 10.0 ],
+    "min" : [ 0.0, 0.0, 0.0 ]
+  }, {
+    "bufferView" : 4,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC4",
+    "max" : [ 0.733, 0.462, 0.191, 1.0 ],
+    "min" : [ 0.0, 0.0, 0.0, 0.462 ]
+  }, {
+    "bufferView" : 5,
+    "byteOffset" : 0,
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