Added support for EXT_mesh_gpu_instancing (#30)

spnda · Sep 6, 2023 · 51b7c61 · 51b7c61
1 parent ee5dd89
commit 51b7c61
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Showing 5 changed files with 78 additions and 7 deletions.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -132,7 +132,7 @@ install(
 if (FASTGLTF_ENABLE_TESTS OR FASTGLTF_ENABLE_EXAMPLES)
     # This is required so that Catch2 compiles with C++17, enabling various features we use in tests.
     if (NOT DEFINED CMAKE_CXX_STANDARD OR CMAKE_CXX_STANDARD STREQUAL "" OR CMAKE_CXX_STANDARD LESS 17)
-        set(CMAKE_CXX_STANDARD 17 CACHE BOOL "C++ standard" FORCE)
+        set(CMAKE_CXX_STANDARD "17" CACHE STRING "C++ standard" FORCE)
     endif()
 
     add_subdirectory(deps)

diff --git a/include/fastgltf/parser.hpp b/include/fastgltf/parser.hpp
@@ -176,6 +176,9 @@ namespace fastgltf {
 
 		// See https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_materials_anisotropy/README.md
 	    KHR_materials_anisotropy = 1 << 18,
+
+        // See https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Vendor/EXT_mesh_gpu_instancing/README.md
+        EXT_mesh_gpu_instancing = 1 << 19,
     };
     // clang-format on
 
@@ -251,6 +254,7 @@ namespace fastgltf {
 
     // String representations of glTF 2.0 extension identifiers.
     namespace extensions {
+        constexpr std::string_view EXT_mesh_gpu_instancing = "EXT_mesh_gpu_instancing";
         constexpr std::string_view EXT_meshopt_compression = "EXT_meshopt_compression";
         constexpr std::string_view EXT_texture_webp = "EXT_texture_webp";
         constexpr std::string_view KHR_lights_punctual = "KHR_lights_punctual";
@@ -274,7 +278,8 @@ namespace fastgltf {
 	// An array of pairs of string representations of extension identifiers and their respective enum
 	// value used for enabling/disabling the loading of it. This also represents all extensions that
 	// fastgltf supports and understands.
-	static constexpr std::array<std::pair<std::string_view, Extensions>, 17> extensionStrings = {{
+	static constexpr std::array<std::pair<std::string_view, Extensions>, 18> extensionStrings = {{
+		{ extensions::EXT_mesh_gpu_instancing,            Extensions::EXT_mesh_gpu_instancing },
 		{ extensions::EXT_meshopt_compression,            Extensions::EXT_meshopt_compression },
 		{ extensions::EXT_texture_webp,                   Extensions::EXT_texture_webp },
 		{ extensions::KHR_lights_punctual,                Extensions::KHR_lights_punctual },

diff --git a/include/fastgltf/types.hpp b/include/fastgltf/types.hpp
@@ -1309,8 +1309,29 @@ namespace fastgltf {
          */
         std::variant<TRS, TransformMatrix> transform;
 
+        /**
+         * Only ever non-empty when EXT_mesh_gpu_instancing is enabled and used by the asset.
+         */
+        std::pmr::vector<std::pair<std::pmr::string, std::size_t>> instancingAttributes;
+
         std::pmr::string name;
-    };
+
+        [[nodiscard]] auto findInstancingAttribute(std::string_view name) noexcept {
+            for (decltype(instancingAttributes)::iterator it = instancingAttributes.begin(); it != instancingAttributes.end(); ++it) {
+                if (it->first == name)
+                    return it;
+            }
+            return instancingAttributes.end();
+        }
+
+        [[nodiscard]] auto findInstancingAttribute(std::string_view name) const noexcept {
+            for (decltype(instancingAttributes)::const_iterator it = instancingAttributes.cbegin(); it != instancingAttributes.cend(); ++it) {
+                if (it->first == name)
+                    return it;
+            }
+            return instancingAttributes.cend();
+        }
+   };
 
     struct Primitive {
 		using attribute_type = std::pair<std::pmr::string, std::size_t>;
@@ -1325,23 +1346,23 @@ namespace fastgltf {
         Optional<std::size_t> indicesAccessor;
         Optional<std::size_t> materialIndex;
 
-		[[nodiscard]] auto findAttribute(std::string_view name) {
+		[[nodiscard]] auto findAttribute(std::string_view name) noexcept {
 			for (decltype(attributes)::iterator it = attributes.begin(); it != attributes.end(); ++it) {
 				if (it->first == name)
 					return it;
 			}
 			return attributes.end();
 		}
 
-		[[nodiscard]] auto findAttribute(std::string_view name) const {
+		[[nodiscard]] auto findAttribute(std::string_view name) const noexcept {
 			for (decltype(attributes)::const_iterator it = attributes.cbegin(); it != attributes.cend(); ++it) {
 				if (it->first == name)
 					return it;
 			}
 			return attributes.cend();
 		}
 
-		[[nodiscard]] auto findTargetAttribute(std::size_t targetIndex, std::string_view name) {
+		[[nodiscard]] auto findTargetAttribute(std::size_t targetIndex, std::string_view name) noexcept {
 			auto& targetAttributes = targets[targetIndex];
 			for (std::remove_reference_t<decltype(targetAttributes)>::iterator it = targetAttributes.begin(); it != targetAttributes.end(); ++it) {
 				if (it->first == name)
@@ -1350,7 +1371,7 @@ namespace fastgltf {
 			return targetAttributes.end();
 		}
 
-		[[nodiscard]] auto findTargetAttribute(std::size_t targetIndex, std::string_view name) const {
+		[[nodiscard]] auto findTargetAttribute(std::size_t targetIndex, std::string_view name) const noexcept {
 			const auto& targetAttributes = targets[targetIndex];
 			for (std::remove_reference_t<decltype(targetAttributes)>::const_iterator it = targetAttributes.cbegin(); it != targetAttributes.cend(); ++it) {
 				if (it->first == name)

diff --git a/src/fastgltf.cpp b/src/fastgltf.cpp
@@ -2737,6 +2737,31 @@ fg::Error fg::Parser::parseNodes(simdjson::dom::array& nodes, Asset& asset) {
                     node.lightIndex = static_cast<std::size_t>(light);
                 }
             }
+
+            dom::object gpuInstancingObject;
+            if (extensionsObject[extensions::EXT_mesh_gpu_instancing].get_object().get(gpuInstancingObject) == SUCCESS) {
+                dom::object attributesObject;
+                if (gpuInstancingObject["attributes"].get_object().get(attributesObject) == SUCCESS) {
+                    auto parseAttributes = [this](dom::object& object, decltype(node.instancingAttributes)& attributes) -> auto {
+                        // We iterate through the JSON object and write each key/pair value into the
+                        // attribute map. The keys are only validated in the validate() method.
+                        attributes = decltype(node.instancingAttributes)(0, resourceAllocator.get());
+                        attributes.reserve(object.size());
+                        for (const auto& field : object) {
+                            const auto key = field.key;
+
+                            std::uint64_t attributeIndex;
+                            if (field.value.get_uint64().get(attributeIndex) != SUCCESS) {
+                                return Error::InvalidGltf;
+                            }
+                            attributes.emplace_back(
+                                std::make_pair(std::pmr::string(key, resourceAllocator.get()), static_cast<std::size_t>(attributeIndex)));
+                        }
+                        return Error::None;
+                    };
+                    parseAttributes(attributesObject, node.instancingAttributes);
+                }
+            }
         }
 
         std::string_view name;

diff --git a/tests/extension_tests.cpp b/tests/extension_tests.cpp
@@ -197,3 +197,23 @@ TEST_CASE("Test KHR_materials_clearcoat", "[gltf-loader]") {
     REQUIRE(materials[7].clearcoat->clearcoatRoughnessTexture->textureIndex == 2);
     REQUIRE(materials[7].clearcoat->clearcoatRoughnessTexture->texCoordIndex == 0);
 }
+
+TEST_CASE("Test EXT_mesh_gpu_instancing", "[gltf-loader]") {
+    auto simpleInstancingTest = sampleModels / "2.0" / "SimpleInstancing" / "glTF";
+    fastgltf::GltfDataBuffer jsonData;
+    REQUIRE(jsonData.loadFromFile(simpleInstancingTest / "SimpleInstancing.gltf"));
+
+    fastgltf::Parser parser(fastgltf::Extensions::EXT_mesh_gpu_instancing);
+    auto asset = parser.loadGLTF(&jsonData, simpleInstancingTest, fastgltf::Options::None, fastgltf::Category::Accessors | fastgltf::Category::Nodes);
+    REQUIRE(asset.error() == fastgltf::Error::None);
+    REQUIRE(fastgltf::validate(asset.get()) == fastgltf::Error::None);
+
+    REQUIRE(asset->accessors.size() >= 6);
+    REQUIRE(asset->nodes.size() >= 1);
+
+    auto& nodes = asset->nodes;
+    REQUIRE(nodes[0].instancingAttributes.size() == 3u);
+    REQUIRE(nodes[0].findInstancingAttribute("TRANSLATION") != nodes[0].instancingAttributes.cend());
+    REQUIRE(nodes[0].findInstancingAttribute("SCALE") != nodes[0].instancingAttributes.cend());
+    REQUIRE(nodes[0].findInstancingAttribute("ROTATION") != nodes[0].instancingAttributes.cend());
+}