From 8c81443f24478ce08ce57b97a7ee57c1106f7072 Mon Sep 17 00:00:00 2001
From: Recep Aslantas <info@recp.me>
Date: Thu, 21 Mar 2024 00:18:02 +0300
Subject: [PATCH] reflect

---
 include/cglm/vec2.h | 17 ++++++++++++++++-
 include/cglm/vec3.h | 16 ++++++++++++++++
 include/cglm/vec4.h | 20 ++++++++++++++++++++
 3 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/include/cglm/vec2.h b/include/cglm/vec2.h
index 5abf616..98e540b 100644
--- a/include/cglm/vec2.h
+++ b/include/cglm/vec2.h
@@ -55,7 +55,7 @@
    CGLM_INLINE void  glm_vec2_clamp(vec2 v, float minVal, float maxVal)
    CGLM_INLINE void  glm_vec2_lerp(vec2 from, vec2 to, float t, vec2 dest)
    CGLM_INLINE void  glm_vec2_make(float * restrict src, vec2 dest)
-
+   CGLM_INLINE void  glm_vec2_reflect(vec2 I, vec2 N, vec2 dest)
  */
 
 #ifndef cglm_vec2_h
@@ -712,4 +712,19 @@ glm_vec2_make(const float * __restrict src, vec2 dest) {
   dest[0] = src[0]; dest[1] = src[1];
 }
 
+/*!
+ * @brief reflection vector using an incident ray and a surface normal
+ *
+ * @param[in]  I    incident vector
+ * @param[in]  N    normalized normal vector
+ * @param[out] dest destination vector for the reflection result
+ */
+CGLM_INLINE
+void
+glm_vec2_reflect(vec2 I, vec2 N, vec2 dest) {
+  vec2 temp;
+  glm_vec2_scale(N, 2.0f * glm_vec2_dot(I, N), temp);
+  glm_vec2_sub(I, temp, dest);
+}
+
 #endif /* cglm_vec2_h */
diff --git a/include/cglm/vec3.h b/include/cglm/vec3.h
index a53cd28..017d1bd 100644
--- a/include/cglm/vec3.h
+++ b/include/cglm/vec3.h
@@ -80,6 +80,7 @@
    CGLM_INLINE void  glm_vec3_smoothinterpc(vec3 from, vec3 to, float t, vec3 dest);
    CGLM_INLINE void  glm_vec3_swizzle(vec3 v, int mask, vec3 dest);
    CGLM_INLINE void  glm_vec3_make(float * restrict src, vec3 dest);
+   CGLM_INLINE void  glm_vec3_reflect(vec3 I, vec3 N, vec3 dest);
 
  Convenient:
    CGLM_INLINE void  glm_cross(vec3 a, vec3 b, vec3 d);
@@ -1202,4 +1203,19 @@ glm_vec3_make(const float * __restrict src, vec3 dest) {
   dest[2] = src[2];
 }
 
+/*!
+ * @brief reflection vector using an incident ray and a surface normal
+ *
+ * @param[in]  I    incident vector
+ * @param[in]  N    normalized normal vector
+ * @param[out] dest reflection result
+ */
+CGLM_INLINE
+void
+glm_vec3_reflect(vec3 I, vec3 N, vec3 dest) {
+  vec3 temp;
+  glm_vec3_scale(N, 2.0f * glm_vec3_dot(I, N), temp);
+  glm_vec3_sub(I, temp, dest);
+}
+
 #endif /* cglm_vec3_h */
diff --git a/include/cglm/vec4.h b/include/cglm/vec4.h
index 8dd5b85..db1bd9c 100644
--- a/include/cglm/vec4.h
+++ b/include/cglm/vec4.h
@@ -65,6 +65,7 @@
    CGLM_INLINE void  glm_vec4_smoothinterpc(vec4 from, vec4 to, float t, vec4 dest);
    CGLM_INLINE void  glm_vec4_swizzle(vec4 v, int mask, vec4 dest);
    CGLM_INLINE void  glm_vec4_make(float * restrict src, vec4 dest);
+   CGLM_INLINE void  glm_vec4_reflect(vec4 I, vec4 N, vec4 dest);
 
  DEPRECATED:
    glm_vec4_dup
@@ -1304,4 +1305,23 @@ glm_vec4_make(const float * __restrict src, vec4 dest) {
   dest[2] = src[2]; dest[3] = src[3];
 }
 
+/*!
+ * @brief reflection vector using an incident ray and a surface normal
+ *
+ * @param[in]  I    incident vector
+ * @param[in]  N    normalized normal vector
+ * @param[out] dest destination vector for the reflection result
+ */
+CGLM_INLINE
+void
+glm_vec4_reflect(vec4 I, vec4 N, vec4 dest) {
+  vec4 temp;
+
+  /* TODO: direct simd touch */
+  glm_vec4_scale(N, 2.0f * glm_vec4_dot(I, N), temp);
+  glm_vec4_sub(I, temp, dest);
+
+  dest[3] = I[3];
+}
+
 #endif /* cglm_vec4_h */