Implement bone matrix computation

animation.c

@@ -0,0 +1,50 @@
+#include "animation.h"
+
+#include <assert.h>
+#include <stdlib.h>
+
+static mat4_t bone_transform(bone_t bone)
+{
+	return mat4_mul(
+	    mat4_translate_vec3(bone.translation),
+	    mat4_mul(
+	        mat4_rotate_quaternion(bone.rotation),
+	        mat4_scale_vec3(bone.scale)));
+}
+
+static void compute_bone_matrices(
+    size_t bone_count, const bone_t *bones,
+    const mat4_t *inverse_bind_matrices, mat4_t *matrices)
+{
+	matrices[0] = bone_transform(bones[0]);
+	for (unsigned i = 1; i < bone_count; ++i) {
+		const mat4_t transform = bone_transform(bones[i]);
+		assert(bones[i].parent < bone_count);
+		matrices[i] = mat4_mul(matrices[bones[i].parent], transform);
+	}
+
+	for (unsigned i = 0; i < bone_count; ++i)
+		matrices[i] = mat4_mul(matrices[i], inverse_bind_matrices[i]);
+}
+
+animation_state_t animation_init(const model_t *model)
+{
+	mat4_t *bone_matrices = calloc(model->bone_count, sizeof(mat4_t));
+	assert(bone_matrices != nullptr);
+	return (animation_state_t) { .bone_matrices = bone_matrices };
+}
+
+void animation_cleanup(animation_state_t *state)
+{
+	if (state->bone_matrices != nullptr) {
+		free(state->bone_matrices);
+		state->bone_matrices = nullptr;
+	}
+}
+
+void animation_update(animation_state_t state, const model_t *model)
+{
+	compute_bone_matrices(
+	    model->bone_count, model->bones, model->inverse_bind_matrices,
+	    state.bone_matrices);
+}