Add mat4_mul_vec3.

__init__.py

@@ -181,6 +181,17 @@ def mat4_lookat(ret, position, lookat):
     assert len(ret) == 16 and len(position) == 3 and len(lookat) == 3
     _mat4_lookat(_mat4(ret), _vec3(position), _vec3(lookat))
 
+_mat4_mul_vec3 = _lib.rk_mat4_mul_vec3
+_mat4_mul_vec3.argtypes = (
+    _vec3_t, # ret
+    _mat4_t, # a
+    _vec3_t, # b
+    ctypes.c_float) # w
+
+def mat4_mul_vec3(ret, a, b, w):
+    assert len(ret) == 3 and len(a) == 16 and len(b) == 3
+    _mat4_mul_vec3(_vec3(ret), _mat4(a), _vec3(b), w)
+
 _mat4_mul_vec4 = _lib.rk_mat4_mul_vec4
 _mat4_mul_vec4.argtypes = (
     _vec4_t, # ret

cpp/math.cpp

@@ -54,6 +54,14 @@ void rk_mat4_lookat(
     ret = glm::lookAtRH(position, lookat, glm::vec3(0.0f, 0.0f, 1.0f));
 }
 
+void rk_mat4_mul_vec3(
+    rk_vec3 & ret,
+    rk_mat4 const & a,
+    rk_vec3 const & b,
+    float const w) {
+    ret = glm::vec3(a * glm::vec4(b, w));
+}
+
 void rk_mat4_mul_vec4(
     rk_vec4 & ret,
     rk_mat4 const & a,

cpp/math.hpp

@@ -53,6 +53,12 @@ RK_EXPORT void rk_mat4_lookat(
     rk_vec3 const & position,
     rk_vec3 const & lookat);
 
+RK_EXPORT void rk_mat4_mul_vec3(
+    rk_vec3 & ret,
+    rk_mat4 const & a,
+    rk_vec3 const & b,
+    float const w);
+
 RK_EXPORT void rk_mat4_mul_vec4(
     rk_vec4 & ret,
     rk_mat4 const & a,