added m4_transform_vec

diff --git a/math_3d.h b/math_3d.h
index 05f71af..2a049fc 100644 (file)
--- a/math_3d.h
+++ b/math_3d.h
@@ -210,7 +210,7 @@ static inline mat4_t m4_mul          (mat4_t a, mat4_t b);
                          mat4_t m4_invert(mat4_t matrix);
               vec3_t m4_mul_pos      (mat4_t matrix, vec3_t position);
               vec3_t m4_mul_dir      (mat4_t matrix, vec3_t direction);
-                         //TODO: implement m4_transform_vec(mat4_t matrix, vec4_t vec);
+                         vec4_t m4_transform_vec(mat4_t matrix, vec4_t vec);
                          //TODO: ref: https://github.com/LWJGL/lwjgl/blob/2df01dd762e20ca0871edb75daf670ccacc89b60/src/java/org/lwjgl/util/vector/Matrix4f.java
 
               void   m4_print        (mat4_t matrix);
@@ -751,4 +751,21 @@ mat4_t m4_invert(mat4_t m)
        return inv;
 }
 
+vec4_t m4_transform_vec(mat4_t m, vec4_t v)
+{
+       vec4_t ret = {0};
+
+       float x = m.m00 * v.x + m.m10 * v.y + m.m20 * v.z + m.m30 * v.w;
+       float y = m.m01 * v.x + m.m11 * v.y + m.m21 * v.z + m.m31 * v.w;
+       float z = m.m02 * v.x + m.m12 * v.y + m.m22 * v.z + m.m32 * v.w;
+       float w = m.m03 * v.x + m.m13 * v.y + m.m23 * v.z + m.m33 * v.w;
+
+       ret.x = x;
+       ret.y = y;
+       ret.z = z;
+       ret.w = w;
+
+       return ret;
+}
+
 #endif // MATH_3D_IMPLEMENTATION