Merge branch '26-asset-loading' of...

Merge branch '26-asset-loading' of gitlab.uni-koblenz.de:vulkan2021/vkcv-framework into 26-asset-loading

Signed-off-by: Tobias Frisch <tfrisch@uni-koblenz.de>

modules/asset_loader/include/vkcv/asset/asset_loader.hpp

@@ -52,6 +52,7 @@ typedef struct {
 	// TODO not yet needed for the first (unlit) triangle
 } Material;
 
+/* This struct describes one vertex attribute of a vertex buffer. */
 typedef struct {
 	PrimitiveType type;		// POSITION, NORMAL, ...
 	uint32_t offset;		// offset in bytes
@@ -61,10 +62,25 @@ typedef struct {
 	uint8_t  componentCount;	// eg. 3 for vec3
 } VertexAttribute;
 
+/* This struct represents one (possibly the only) part of a mesh. There is
+ * always one vertexBuffer and zero or one indexBuffer (indexed rendering is
+ * common but not always used). If there is no indexBuffer, this is indicated
+ * by indexBuffer.data being NULL.
+ * Each vertex buffer can have one or more vertex attributes.
+ * Note that the indexBuffer and vertexBuffer might be pointing to the same
+ * block of memory.
+ * 
+ * TODO For now, the caller of loadMesh() has to free this memory when they are
+ * done, but since this is not generally good practice in C++, this behaviour
+ * will likely be changed later. */
 typedef struct {
 	enum PrimitiveMode mode;	// draw as points, lines or triangle?
 	size_t numIndices, numVertices;
-	uint32_t *indexBuffer;		// array of indices for indexed rendering
+	struct {
+		void *data;		// binary data of the index buffer
+		size_t byteLength;	// length of the index buffer
+		uint32_t byteOffset;	// offset into the buffer in bytes
+	} indexBuffer;
 	struct {
 		void *data;		// the binary data of the buffer
 		size_t byteLength;	// the length of the entire buffer in bytes
@@ -75,7 +91,8 @@ typedef struct {
 	uint8_t materialIndex;		// index to one of the meshes materials
 } VertexGroup;
 
-/* This struct represents a single mesh loaded from a glTF file. */
+/* This struct represents a single mesh loaded from a glTF file. It consists of
+ * at least one VertexVroup and any number of Materials. */
 typedef struct {
 	std::string name;
 	std::vector<VertexGroup> vertexGroups;

modules/asset_loader/src/vkcv/asset/asset_loader.cpp

@@ -6,20 +6,40 @@
 namespace vkcv::asset {
 	
 	int loadMesh(const std::string &path, Mesh &mesh) {
-		std::vector<uint8_t> v;
+		// TODO load the gltf file using the library, return 0 if there is an
+		// error.
+		// If the library throws excaptions, catch them and maybe print an
+		// error, but do not pass on the exception to the caller!
+		// Looking at the example code of fx-gltf I would assume that
+		// fx::gltf::LoadFromText(); is a good starting point.
 		
-		if (fx::base64::TryDecode(path, v)) {
-			for (auto& ve : v) {
-				std::cout << ve << " ";
-			}
-			
-			std::cout << std::endl;
-		} else {
-			std::cerr << "Schade!" << std::endl;
-		}
+		// TODO Verify that all required information can be found in the
+		// struct/class returned by fx-gltf (eg. check if there is exactly one
+		// mesh and that it has at least 3 vertices or something like that) and
+		// return 0 if something is missing.
+		// The important thing here is that we don't create an incomplete mesh
+		// because we start copying data before making sure all the required
+		// data is available.
 		
-		// TODO
-		return -1;
+		// TODO Fill the output argument 'mesh' with the data from the loaded
+		// glTF file.
+		// Look at the structs 'Mesh', 'VertexGroup' and 'VertexAttribute'
+		// defined in asset_loader.hpp and compare it to the glTF cheat sheet:
+		// https://raw.githubusercontent.com/KhronosGroup/glTF/master/specification/2.0/figures/gltfOverview-2.0.0b.png
+		//
+		// If the fx::gltf::Document struct/class from the fx-gltf library
+		// don't really match our structs, we may need to re-think how our
+		// structs are defined (they are only based on the glTF specification).
+		//
+		// In the first iteration our goal is to simply load the vertices of a
+		// mesh without textures and materials. (Maybe start with our triangle
+		// since that does not have textures)
+		// Once this works, we can add support for materials/textures, but I
+		// wouldn't include this feature until loading of vertices+indices is
+		// proven to work
+		
+		// Finally return 1 to signal that all is fine
+		return 1;
 	}
 
 }

projects/first_mesh/src/main.cpp

@@ -6,7 +6,7 @@ int main(int argc, const char** argv) {
 	
 	int result = vkcv::asset::loadMesh("test.gltf", mesh);
 	
-	if (result == 0) {
+	if (result == 1) {
 		std::cout << "Mesh loading successful!" << std::endl;
 	} else {
 		std::cout << "Mesh loading failed: " << result << std::endl;