Implement linear interpolation between animation keyframes

linear_alg.h

@@ -71,12 +71,18 @@ typedef struct {
 	}
 // clang-format on
 
+vec3_t vec3_add(vec3_t v, vec3_t u);
 vec3_t vec3_sub(vec3_t v, vec3_t u);
+vec3_t vec3_scale(float s, vec3_t v);
 float vec3_len(vec3_t v);
 vec3_t vec3_norm(vec3_t v);
 float vec3_dot(vec3_t v, vec3_t u);
 vec3_t vec3_cross(vec3_t v, vec3_t u);
 
+vec4_t vec4_add(vec4_t v, vec4_t u);
+vec4_t vec4_scale(float s, vec4_t v);
+float vec4_dot(vec4_t v, vec4_t u);
+
 mat4_t mat4_mul(mat4_t m, mat4_t n);
 mat4_t mat4_lookat(vec3_t camera, vec3_t target, vec3_t up);
 mat4_t mat4_perspective(float aspect, float fov, float near, float far);