[#57] Define Material, Texture and Sampler struct.

This commit only defines the structs and makes sure that the
construction is still valid, but does not implement the usage of the new
structs.

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

@@ -50,11 +50,51 @@ enum PrimitiveMode {
 	POINTS=0, LINES, LINELOOP, LINESTRIP, TRIANGLES, TRIANGLESTRIP,
 	TRIANGLEFAN
 };
+
 /* The indices in the index buffer can be of different bit width. */
 enum IndexType { UINT32=0, UINT16=1, UINT8=2 };
 
+/* Flags for the bit-mask in the Material struct. Use the bitof() macro to
+ * translate the enums value when checking a flag of the mask:
+ * Material mat = ...;
+ * if (mat.textureMask & bitflag(PBRTextureTarget::baseColor)) {...} */
+// TODO Maybe it's easier to replace the bitflag() macro with a "hasTexture()"
+// macro that already combines the logical AND with the bitflag?
+enum class PBRTextureTarget {
+	baseColor=1, metalRough=2, normal=4, occlusion=8, emissive=16
+};
+
+/* This macro translates the index of an enum in the defined order to an
+ * integer with a single bit set in the corresponding place. */
+#define bitflag(ENUM) (0x1u << (ENUM))
+
+typedef struct {
+	// TODO define struct for samplers (low priority)
+} Sampler;
+
+typedef struct {
+	uint8_t sampler;	// index into the Meshes samplers array
+	uint8_t channels;	// number of channels
+	uint16_t w, h;		// width and height of the texture
+	std::vector<uint8_t> data;	// binary data of the decoded texture
+} Texture;
+
+/* The asset loader module only supports the PBR-MetallicRoughness model for
+ * materials.
+ * NOTE: Only a single UV-texture is currently supported to reduce the
+ * complexity at first. Later, there will need to be an association between
+ * each of the texture targets in the Material struct and a VertexAttribute of
+ * a VertexBuffer that defines the UV coordinates for that texture. */
 typedef struct {
-	// TODO not yet needed for the first (unlit) triangle
+	uint8_t textureMask;	// bit mask with active texture targets
+	// Indices into the Mesh.textures array
+	uint8_t baseColor, metalRough, normal, occlusion, emissive;
+	// Scaling factors for each texture target
+	struct { float r, g, b, a; } baseColorFactor;
+	float metallicFactor, roughnessFactor;
+	float normalScale;
+	float occlusionStrength;
+	struct { float r, g, b; } emissiveFactor;
 } Material;
 
 /* This struct represents one (possibly the only) part of a mesh. There is
@@ -84,6 +124,10 @@ typedef struct {
 	std::string name;
 	std::vector<VertexGroup> vertexGroups;
 	std::vector<Material> materials;
+	std::vector<Texture> textures;
+	std::vector<Sampler> samplers;
+	// TODO Replace usage of the texture_hack everywhere with use of the
+	// textures, materials and sampler-arrays.
 	// FIXME Dirty hack to get one(!) texture for our cube demo
 	// hardcoded to always have RGBA channel layout
 	struct {

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

@@ -173,11 +173,15 @@ int loadMesh(const std::string &path, Mesh &mesh) {
 	});
 	
 	std::vector<Material> materials;
+	std::vector<Texture> textures;
+	std::vector<Sampler> samplers;
 
 	mesh = {
 		object.meshes[0].name,
 		vertexGroups,
 		materials,
+		textures,
+		samplers,
 		0, 0, 0, NULL
 	};