PBR extension: emissive strength

assets/example_meshes/gltf/CompareEmissiveStrength/CompareEmissiveStrength.gltf

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+  "asset": {
+    "copyright": "Asset CC0, created by Eric Chadwick and DGG. glTF logo © 2017, Khronos Group.",
+    "generator": "Created by RapidCompact v6.8.1 | www.rapidcompact.com",
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+  "extensionsUsed": [
+    "KHR_materials_emissive_strength"
+  ],
+  "images": [
+    {
+      "uri": "Compare_Emissive-Strength_img0.jpg"
+    }
+  ],
+  "materials": [
+    {
+      "emissiveFactor": [
+        1,
+        1,
+        1
+      ],
+      "emissiveTexture": {
+        "index": 0
+      },
+      "name": "glTF Logo Emissive",
+      "pbrMetallicRoughness": {
+        "baseColorFactor": [
+          0,
+          0,
+          0,
+          1
+        ],
+        "metallicFactor": 0,
+        "roughnessFactor": 0
+      }
+    },
+    {
+      "emissiveFactor": [
+        1,
+        1,
+        1
+      ],
+      "emissiveTexture": {
+        "index": 0
+      },
+      "extensions": {
+        "KHR_materials_emissive_strength": {
+          "emissiveStrength": 3
+        }
+      },
+      "name": "glTF Logo Emissive Strength",
+      "pbrMetallicRoughness": {
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+          0,
+          0,
+          0,
+          1
+        ],
+        "metallicFactor": 0,
+        "roughnessFactor": 0
+      }
+    }
+  ],
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+      ]
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+        }
+      ]
+    }
+  ],
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+  "scenes": [
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+  ],
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+    }
+  ]
+}

examples/render/950-pbr/main.cpp

@@ -36,6 +36,7 @@ int main(int argc, char** argv)
         NORMAL_TENGENT_MIRROR_TEST,
         COMPARE_AMBIENT_OCCLUSION,
         DAMAGED_HELMET,
+        COMPARE_EMISSIVE_STRENGTH,
         COUNT_EXAMPLES
     };
 
@@ -44,9 +45,11 @@ 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/CompareEmissiveStrength/CompareEmissiveStrength.gltf"
+    };
 
-    uint selectedExample = METAL_ROUGH_SPHERES;
+    uint selectedExample = COMPARE_EMISSIVE_STRENGTH;
 
     enum PanoramasExamples {
         COLOSSEUM_HDR,
@@ -120,6 +123,7 @@ int main(int argc, char** argv)
             std::cout << "  normalScale: " << mat.normalScale() << std::endl;
             std::cout << "  occlusionStrength: " << mat.occlusionStrength()
                       << std::endl;
+            std::cout << "  emissiveStrength: " << mat.emissiveStrength() << std::endl;
             printTextureInfo(mat, BASE_COLOR);
             printTextureInfo(mat, METALLIC_ROUGHNESS);
             printTextureInfo(mat, NORMAL);

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

@@ -62,6 +62,10 @@ int loadGltfPrimitiveMaterial(
         bool   doubleSided;
         int    baseColorTextureId, metallicRoughnessTextureId, normalTextureId,
             occlusionTextureId, emissiveTextureId;
+
+        // extensions data
+        double emissiveStrength = 1.0f;
+
         const tinygltf::Material& mat = model.materials[p.material];
 
         std::string matName = mat.name;
@@ -122,6 +126,16 @@ int loadGltfPrimitiveMaterial(
         // occlusionStrength
         occlusionStrength = mat.occlusionTexture.strength;
 
+        // extensions
+        if(mat.extensions.contains("KHR_materials_emissive_strength")) {
+            const auto& emissiveStrengthExt =
+                mat.extensions.at("KHR_materials_emissive_strength");
+            if(emissiveStrengthExt.Has("emissiveStrength"))
+                emissiveStrength = emissiveStrengthExt
+                    .Get("emissiveStrength")
+                    .GetNumberAsDouble();
+        }
+
         // function to load a texture in a material
         auto loadTextureInMaterial = [&](Material&             mat,
                                          int                   textureId,
@@ -195,6 +209,7 @@ int loadGltfPrimitiveMaterial(
             mat.doubleSided()       = doubleSided;
             mat.normalScale()       = normalScale;
             mat.occlusionStrength() = occlusionStrength;
+            mat.emissiveStrength()  = emissiveStrength;
             loadTextureInMaterial(
                 mat, baseColorTextureId, Material::TextureType::BASE_COLOR);
             loadTextureInMaterial(