Load inverse bind matrices into model

model.c

@@ -29,6 +29,10 @@ void model_cleanup(model_t *m)
 	if (m->bones != nullptr) {
 		free(m->bones);
 		m->bones = nullptr;
-		m->bone_count = 0;
 	}
+	if (m->inverse_bind_matrices != nullptr) {
+		free(m->inverse_bind_matrices);
+		m->inverse_bind_matrices = nullptr;
+	}
+    m->vertex_count = m->index_count = m->bone_count = 0;
 }

model.h

@@ -26,6 +26,7 @@ typedef struct {
 	vertex_t *vertices;
 	index_t *indices;
 	bone_t *bones;
+	mat4_t *inverse_bind_matrices;
 	size_t vertex_count;
 	size_t index_count;
 	size_t bone_count;

model_format_glb.c

@@ -98,6 +98,7 @@ typedef struct {
 	accessor_t bone_indices;
 	accessor_t weights;
 	accessor_t indices;
+	accessor_t inverse_bind_matrices;
 } accessors_t;
 
 typedef struct {
@@ -112,6 +113,7 @@ typedef struct {
 	view_t bone_indices;
 	view_t weights;
 	view_t indices;
+	view_t inverse_bind_matrices;
 } views_t;
 
 typedef struct {
@@ -126,6 +128,7 @@ typedef struct {
 	gltf_info_member_t bone_indices;
 	gltf_info_member_t weights;
 	gltf_info_member_t indices;
+	gltf_info_member_t inverse_bind_matrices;
 	size_t vertex_count, index_count, bone_count;
 } gltf_info_t;
 
@@ -580,7 +583,7 @@ static accessor_t read_accessor(const uint8_t **p)
 	return accessor;
 }
 
-static accessors_t read_accessors(const uint8_t *p, mesh_t mesh)
+static accessors_t read_accessors(const uint8_t *p, mesh_t mesh, skin_t skin)
 {
 	accessors_t accessors = {};
 	assert(*p == '[');
@@ -596,11 +599,20 @@ static accessors_t read_accessors(const uint8_t *p, mesh_t mesh)
 			accessors.weights = read_accessor(&p);
 		else if (i == mesh.indices)
 			accessors.indices = read_accessor(&p);
+		else if (i == skin.inverse_bind_matrices)
+			accessors.inverse_bind_matrices = read_accessor(&p);
 		else
 			skip_value(&p);
 		if (*p == ',')
 			++p;
 	}
+
+	assert(accessors.normals.count != 0);
+	assert(accessors.positions.count != 0);
+	assert(accessors.bone_indices.count != 0);
+	assert(accessors.weights.count != 0);
+	assert(accessors.indices.count != 0);
+	assert(accessors.inverse_bind_matrices.count != 0);
 	return accessors;
 }
 
@@ -652,6 +664,8 @@ static views_t read_views(const uint8_t *p, accessors_t accessors)
 			views.weights = read_view(&p);
 		else if (i == accessors.indices.view)
 			views.indices = read_view(&p);
+		else if (i == accessors.inverse_bind_matrices.view)
+			views.inverse_bind_matrices = read_view(&p);
 		else
 			skip_value(&p);
 
@@ -667,6 +681,7 @@ static views_t read_views(const uint8_t *p, accessors_t accessors)
 	assert(views.bone_indices.len != 0);
 	assert(views.weights.len != 0);
 	assert(views.indices.len != 0);
+	assert(views.inverse_bind_matrices.len != 0);
 	return views;
 }
 
@@ -728,7 +743,7 @@ static gltf_info_t read_json(const uint8_t *json)
 	assert(bones != nullptr);
 	read_joints(nodes_json, skin, bones);
 
-	const accessors_t accessors = read_accessors(accessors_json, mesh);
+	const accessors_t accessors = read_accessors(accessors_json, mesh, skin);
 	const views_t views = read_views(views_json, accessors);
 
 	// Verify data types
@@ -747,6 +762,9 @@ static gltf_info_t read_json(const uint8_t *json)
 	assert(
 	    accessors.indices.component == COMPONENT_TYPE_U16
 	    && accessors.indices.type == ACCESSOR_TYPE_SCALAR);
+	assert(
+	    accessors.inverse_bind_matrices.component == COMPONENT_TYPE_F32
+	    && accessors.inverse_bind_matrices.type == ACCESSOR_TYPE_MAT4);
 
 	// Ensure the vertex count is consistent
 	assert(
@@ -754,6 +772,9 @@ static gltf_info_t read_json(const uint8_t *json)
 	    && accessors.positions.count == accessors.bone_indices.count
 	    && accessors.positions.count == accessors.weights.count);
 
+	// Ensure the joint count is consistent
+	assert(accessors.inverse_bind_matrices.count == skin.joint_count);
+
 	return (gltf_info_t) {
 		.bones = bones,
 		.positions = info_member(accessors.positions, views.positions),
@@ -764,6 +785,8 @@ static gltf_info_t read_json(const uint8_t *json)
 		.indices = info_member(accessors.indices, views.indices),
 		.vertex_count = accessors.positions.count,
 		.index_count = accessors.indices.count,
+		.inverse_bind_matrices = info_member(
+		    accessors.inverse_bind_matrices, views.inverse_bind_matrices),
 		.bone_count = skin.joint_count,
 	};
 }
@@ -817,6 +840,12 @@ model_t model_format_glb_read(const char *path)
 	    (const u16_vec4_t *)(bin_data + info.bone_indices.offset),
 	    (const vec4_t *)(bin_data + info.weights.offset), info.vertex_count);
 	memcpy(model.indices, bin_data + info.indices.offset, info.indices.len);
+	model.inverse_bind_matrices = calloc(info.bone_count, sizeof(mat4_t));
+	assert(model.inverse_bind_matrices != nullptr);
+	memcpy(
+	    model.inverse_bind_matrices,
+	    bin_data + info.inverse_bind_matrices.offset,
+	    info.inverse_bind_matrices.len);
 
 	munmap(file, len);
 	return model;