PBR extension: anisotropy

assets/example_meshes/gltf/CarbonFibre/CarbonFibre.gltf

@@ -0,0 +1,181 @@
+{
+    "asset": {
+        "version": "2.0",
+        "generator": "3ds Max, Max2Babylon, Visual Studio Code, glTF Tools",
+        "copyright": "(C) 2023, Wayfair LLC. CC-BY 4.0 International https://creativecommons.org/licenses/by/4.0/. Model and textures created by Eric Chadwick."
+    },
+    "scene": 0,
+    "scenes": [
+        {
+            "nodes": [
+                0
+            ]
+        }
+    ],
+    "nodes": [
+        {
+            "mesh": 0,
+            "translation": [
+                0.0,
+                0.5,
+                0.0
+            ],
+            "name": "CarbonFibre"
+        }
+    ],
+    "meshes": [
+        {
+            "primitives": [
+                {
+                    "attributes": {
+                        "POSITION": 1,
+                        "NORMAL": 2,
+                        "TEXCOORD_0": 3
+                    },
+                    "indices": 0,
+                    "material": 0
+                }
+            ],
+            "name": "CarbonFibre"
+        }
+    ],
+    "accessors": [
+        {
+            "bufferView": 0,
+            "componentType": 5123,
+            "count": 11904,
+            "type": "SCALAR",
+            "name": "accessorIndices"
+        },
+        {
+            "bufferView": 1,
+            "componentType": 5126,
+            "count": 2129,
+            "max": [
+                0.5,
+                0.5,
+                0.5
+            ],
+            "min": [
+                -0.5,
+                -0.5,
+                -0.5
+            ],
+            "type": "VEC3",
+            "name": "accessorPositions"
+        },
+        {
+            "bufferView": 1,
+            "byteOffset": 25548,
+            "componentType": 5126,
+            "count": 2129,
+            "type": "VEC3",
+            "name": "accessorNormals"
+        },
+        {
+            "bufferView": 2,
+            "componentType": 5126,
+            "count": 2129,
+            "type": "VEC2",
+            "name": "accessorUVs"
+        }
+    ],
+    "bufferViews": [
+        {
+            "buffer": 0,
+            "byteLength": 23808,
+            "name": "bufferViewScalar",
+            "target": 34963
+        },
+        {
+            "buffer": 0,
+            "byteOffset": 23808,
+            "byteLength": 51096,
+            "byteStride": 12,
+            "name": "bufferViewFloatVec3",
+            "target": 34962
+        },
+        {
+            "buffer": 0,
+            "byteOffset": 74904,
+            "byteLength": 17032,
+            "byteStride": 8,
+            "name": "bufferViewFloatVec2",
+            "target": 34962
+        }
+    ],
+    "buffers": [
+        {
+            "uri": "CarbonFibre.bin",
+            "byteLength": 91936
+        }
+    ],
+    "extensionsUsed": [
+        "KHR_materials_anisotropy"
+    ],
+    "images": [
+        {
+            "uri": "CarbonFibre_occlusion.png"
+        },
+        {
+            "uri": "CarbonFibre_normal.png"
+        },
+        {
+            "uri": "CarbonFibre_anisotropy.png"
+        }
+    ],
+    "textures": [
+        {
+            "name": "CarbonFibre_occlusion.png",
+            "sampler": 0,
+            "source": 0
+        },
+        {
+            "name": "CarbonFibre_normal.png",
+            "sampler": 0,
+            "source": 1
+        },
+        {
+            "name": "CarbonFibre_anisotropy.png",
+            "sampler": 0,
+            "source": 2
+        }
+    ],
+    "materials": [
+        {
+            "name": "CarbonFibre",
+            "pbrMetallicRoughness": {
+                "baseColorFactor": [
+                    0.009,
+                    0.009,
+                    0.009,
+                    1.0
+                ],
+                "metallicFactor": 0,
+                "roughnessFactor": 0.4
+            },
+            "normalTexture": {
+                "index": 1,
+                "scale": 2
+            },
+            "occlusionTexture": {
+                "index": 0
+            },
+            "extensions": {
+                "KHR_materials_anisotropy": {
+                    "anisotropyStrength": 0.5,
+                    "anisotropyRotation": 0,
+                    "anisotropyTexture": {
+                        "index": 2
+                    }
+                }
+            }
+        }
+    ],
+    "samplers": [
+        {
+            "magFilter": 9729,
+            "minFilter": 9987
+        }
+    ]
+}

examples/render/950-pbr/main.cpp

@@ -36,6 +36,8 @@ int main(int argc, char** argv)
         NORMAL_TENGENT_MIRROR_TEST,
         COMPARE_AMBIENT_OCCLUSION,
         DAMAGED_HELMET,
+        ANISOTROPY_ROTATION_TEST,
+        CARBON_FIBRE,
         COUNT_EXAMPLES
     };
 
@@ -44,9 +46,11 @@ int main(int argc, char** argv)
         "/gltf/MetalRoughSpheres/MetalRoughSpheres.gltf",
         "/gltf/NormalTangentMirrorTest/NormalTangentMirrorTest.gltf",
         "/gltf/CompareAmbientOcclusion/CompareAmbientOcclusion.gltf",
-        "/gltf/DamagedHelmet/DamagedHelmet.gltf"};
+        "/gltf/DamagedHelmet/DamagedHelmet.gltf",
+        "/gltf/AnisotropyRotationTest/AnisotropyRotationTest.gltf",
+        "/gltf/CarbonFibre/CarbonFibre.gltf"};
 
-    uint selectedExample = METAL_ROUGH_SPHERES;
+    uint selectedExample = CARBON_FIBRE;
 
     enum PanoramasExamples {
         COLOSSEUM_HDR,
@@ -66,7 +70,7 @@ int main(int argc, char** argv)
         "/panoramas/uffizi.hdr",
         "/panoramas/uffizi.ktx"};
 
-    uint selectedPanorama = UFFIZI_KTX;
+    uint selectedPanorama = COLOSSEUM_HDR;
 
     std::vector<vcl::TriMesh> meshes = vcl::loadMeshes<vcl::TriMesh>(
         VCLIB_EXAMPLE_MESHES_PATH + gltfExampleFilenames[selectedExample]);
@@ -88,6 +92,9 @@ int main(int argc, char** argv)
         else if (type == EMISSIVE) {
             typeName = "emissive";
         }
+        else if (type == ANISOTROPY) {
+            typeName = "anisotropy";
+        }
 
         std::cout << "  " << typeName << "Texture: ";
         if (!texture.isNull()) {
@@ -120,11 +127,16 @@ int main(int argc, char** argv)
             std::cout << "  normalScale: " << mat.normalScale() << std::endl;
             std::cout << "  occlusionStrength: " << mat.occlusionStrength()
                       << std::endl;
+            std::cout << "  anisotropyStrength: " << mat.anisotropyStrength()
+                      << std::endl;
+            std::cout << "  anisotropyRotation: " << mat.anisotropyRotation()
+                      << std::endl;
             printTextureInfo(mat, BASE_COLOR);
             printTextureInfo(mat, METALLIC_ROUGHNESS);
             printTextureInfo(mat, NORMAL);
             printTextureInfo(mat, OCCLUSION);
             printTextureInfo(mat, EMISSIVE);
+            printTextureInfo(mat, ANISOTROPY);
             std::cout << "  ------------------------" << std::endl;
         }
         std::cout << "------------------------" << std::endl;

vclib/core/include/vclib/io/mesh/gltf/detail/load_mesh.h

@@ -62,6 +62,11 @@ int loadGltfPrimitiveMaterial(
         bool   doubleSided;
         int    baseColorTextureId, metallicRoughnessTextureId, normalTextureId,
             occlusionTextureId, emissiveTextureId;
+
+        double anisotropyStrength = 0.0;
+        double anisotropyRotation = 0.0;
+        int anisotropyTextureId = -1;
+
         const tinygltf::Material& mat = model.materials[p.material];
 
         std::string matName = mat.name;
@@ -122,6 +127,32 @@ int loadGltfPrimitiveMaterial(
         // occlusionStrength
         occlusionStrength = mat.occlusionTexture.strength;
 
+        // anisotropy
+        if (mat.extensions.contains("KHR_materials_anisotropy")) {
+            const auto& anisotropyExt =
+                mat.extensions.at("KHR_materials_anisotropy");
+
+            if (anisotropyExt.Has("anisotropyStrength")) {
+                anisotropyStrength = anisotropyExt
+                    .Get("anisotropyStrength")
+                    .GetNumberAsDouble();
+                anisotropyStrength = std::clamp(anisotropyStrength, 0.0, 1.0);
+            }
+
+            if (anisotropyExt.Has("anisotropyRotation")) {
+                anisotropyRotation = anisotropyExt
+                    .Get("anisotropyRotation")
+                    .GetNumberAsDouble();
+            }
+
+            if (anisotropyExt.Has("anisotropyTexture")) {
+                auto& tex = anisotropyExt.Get("anisotropyTexture");
+                if (tex.Has("index")) {
+                    anisotropyTextureId = tex.Get("index").GetNumberAsInt();
+                }
+            }
+        }
+
         // function to load a texture in a material
         auto loadTextureInMaterial = [&](Material&             mat,
                                          int                   textureId,
@@ -185,16 +216,18 @@ int loadGltfPrimitiveMaterial(
 
         if constexpr (HasMaterials<MeshType>) {
             Material mat;
-            mat.name()              = matName;
-            mat.baseColor()         = baseColor;
-            mat.metallic()          = metallic;
-            mat.roughness()         = roughness;
-            mat.emissiveColor()     = emissiveColor;
-            mat.alphaMode()         = alphaMode;
-            mat.alphaCutoff()       = alphaCutoff;
-            mat.doubleSided()       = doubleSided;
-            mat.normalScale()       = normalScale;
-            mat.occlusionStrength() = occlusionStrength;
+            mat.name()               = matName;
+            mat.baseColor()          = baseColor;
+            mat.metallic()           = metallic;
+            mat.roughness()          = roughness;
+            mat.emissiveColor()      = emissiveColor;
+            mat.alphaMode()          = alphaMode;
+            mat.alphaCutoff()        = alphaCutoff;
+            mat.doubleSided()        = doubleSided;
+            mat.normalScale()        = normalScale;
+            mat.occlusionStrength()  = occlusionStrength;
+            mat.anisotropyStrength() = anisotropyStrength;
+            mat.anisotropyRotation() = anisotropyRotation;
             loadTextureInMaterial(
                 mat, baseColorTextureId, Material::TextureType::BASE_COLOR);
             loadTextureInMaterial(
@@ -207,6 +240,8 @@ int loadGltfPrimitiveMaterial(
                 mat, occlusionTextureId, Material::TextureType::OCCLUSION);
             loadTextureInMaterial(
                 mat, emissiveTextureId, Material::TextureType::EMISSIVE);
+            loadTextureInMaterial(
+                mat, anisotropyTextureId, Material::TextureType::ANISOTROPY);
             m.pushMaterial(mat);
             idx = m.materialCount() - 1; // index of the added material
             if constexpr (HasColor<MeshType>) {