change signature of refraction to let caller know if refraction occurs or not

include/cglm/call/vec2.h

@@ -202,7 +202,7 @@ void
 glmc_vec2_reflect(vec2 I, vec2 N, vec2 dest);
 
 CGLM_EXPORT
-void
+bool
 glmc_vec2_refract(vec2 I, vec2 N, float eta, vec2 dest);
 
 #ifdef __cplusplus

include/cglm/call/vec3.h

@@ -343,7 +343,7 @@ void
 glmc_vec3_reflect(vec3 I, vec3 N, vec3 dest);
 
 CGLM_EXPORT
-void
+bool
 glmc_vec3_refract(vec3 I, vec3 N, float eta, vec3 dest);
 
 #ifdef __cplusplus

include/cglm/call/vec4.h

@@ -316,7 +316,7 @@ void
 glmc_vec4_reflect(vec4 I, vec4 N, vec4 dest);
 
 CGLM_EXPORT
-void
+bool
 glmc_vec4_refract(vec4 I, vec4 N, float eta, vec4 dest);
 
 #ifdef __cplusplus

include/cglm/struct/vec2.h

@@ -55,7 +55,7 @@
    CGLM_INLINE vec2s glms_vec2_lerp(vec2s from, vec2s to, float t)
    CGLM_INLINE vec2s glms_vec2_make(float * restrict src)
    CGLM_INLINE vec2s glms_vec2_reflect(vec2s I, vec2s N)
-   CGLM_INLINE vec2s glms_vec2_refract(vec2s I, vec2s N, float eta)
+   CGLM_INLINE bool  glms_vec2_refract(vec2s I, vec2s N, float eta, vec2s *dest)
  */
 
 #ifndef cglms_vec2s_h
@@ -709,22 +709,23 @@ glms_vec2_(reflect)(vec2s I, vec2s N) {
 }
 
 /*!
- * @brief refraction vector using entering ray, surface normal and refraction index
+ * @brief computes refraction vector for an incident vector and a surface normal.
  *
- * if the angle between the entering ray I and the surface normal N is too great
- * for a given refraction index, the return value is zero
+ * calculates the refraction vector based on Snell's law. If total internal reflection
+ * occurs (angle too great given eta), dest is set to zero and returns false.
+ * Otherwise, computes refraction vector, stores it in dest, and returns true.
  *
  * @param[in]  I    normalized incident vector
  * @param[in]  N    normalized normal vector
- * @param[in]  eta  ratio of indices of refraction
- * @param[out] dest refraction result
+ * @param[in]  eta  ratio of indices of refraction (incident/transmitted)
+ * @param[out] dest refraction vector if refraction occurs; zero vector otherwise
+ *
+ * @returns true if refraction occurs; false if total internal reflection occurs.
  */
 CGLM_INLINE
-vec2s
-glms_vec2_(refract)(vec2s I, vec2s N, float eta) {
-  vec2s dest;
-  glm_vec2_refract(I.raw, N.raw, eta, dest.raw);
-  return dest;
+bool
+glms_vec2_(refract)(vec2s I, vec2s N, float eta, vec2s * __restrict dest) {
+  return glm_vec2_refract(I.raw, N.raw, eta, dest->raw);
 }
 
 #endif /* cglms_vec2s_h */

include/cglm/struct/vec3.h

@@ -78,7 +78,7 @@
    CGLM_INLINE vec3s glms_vec3_make(float * restrict src);
    CGLM_INLINE vec3s glms_vec3_faceforward(vec3s N, vec3s I, vec3s Nref);
    CGLM_INLINE vec3s glms_vec3_reflect(vec3s I, vec3s N);
-   CGLM_INLINE vec3s glms_vec3_refract(vec3s I, vec3s N, float eta);
+   CGLM_INLINE bool  glms_vec3_refract(vec3s I, vec3s N, float eta, vec3s *dest)
 
  Convenient:
    CGLM_INLINE vec3s glms_cross(vec3s a, vec3s b);
@@ -1120,22 +1120,23 @@ glms_vec3_(reflect)(vec3s I, vec3s N) {
 }
 
 /*!
- * @brief refraction vector using entering ray, surface normal and refraction index
+ * @brief computes refraction vector for an incident vector and a surface normal.
  *
- * if the angle between the entering ray I and the surface normal N is too great
- * for a given refraction index, the return value is zero
+ * calculates the refraction vector based on Snell's law. If total internal reflection
+ * occurs (angle too great given eta), dest is set to zero and returns false.
+ * Otherwise, computes refraction vector, stores it in dest, and returns true.
  *
  * @param[in]  I    normalized incident vector
  * @param[in]  N    normalized normal vector
- * @param[in]  eta  ratio of indices of refraction
- * @returns refraction result
+ * @param[in]  eta  ratio of indices of refraction (incident/transmitted)
+ * @param[out] dest refraction vector if refraction occurs; zero vector otherwise
+ *
+ * @returns true if refraction occurs; false if total internal reflection occurs.
  */
 CGLM_INLINE
-vec3s
-glms_vec3_(refract)(vec3s I, vec3s N, float eta) {
-  vec3s dest;
-  glm_vec3_refract(I.raw, N.raw, eta, dest.raw);
-  return dest;
+bool
+glms_vec3_(refract)(vec3s I, vec3s N, float eta, vec3s * __restrict dest) {
+  return glm_vec3_refract(I.raw, N.raw, eta, dest->raw);
 }
 
 #endif /* cglms_vec3s_h */

include/cglm/struct/vec4.h

@@ -68,7 +68,7 @@
    CGLM_INLINE vec4s glms_vec4_swizzle(vec4s v, int mask);
    CGLM_INLINE vec4s glms_vec4_make(float * restrict src);
    CGLM_INLINE vec4s glms_vec4_reflect(vec4s I, vec4s N);
-   CGLM_INLINE vec4s glms_vec4_refract(vec4s I, vec4s N, float eta);
+   CGLM_INLINE bool  glms_vec4_refract(vec4s I, vec4s N, float eta, vec4s *dest)
  */
 
 #ifndef cglms_vec4s_h
@@ -945,10 +945,11 @@ glms_vec4_(reflect)(vec4s I, vec4s N) {
 }
 
 /*!
- * @brief refraction vector using entering ray, surface normal and refraction index
+ * @brief computes refraction vector for an incident vector and a surface normal.
  *
- * if the angle between the entering ray I and the surface normal N is too great
- * for a given refraction index, the return value is zero
+ * calculates the refraction vector based on Snell's law. If total internal reflection
+ * occurs (angle too great given eta), dest is set to zero and returns false.
+ * Otherwise, computes refraction vector, stores it in dest, and returns true.
  *
  * this implementation does not explicitly preserve the 'w' component of the
  * incident vector 'I' in the output 'dest', users requiring the preservation of
@@ -956,15 +957,15 @@ glms_vec4_(reflect)(vec4s I, vec4s N) {
  *
  * @param[in]  I    normalized incident vector
  * @param[in]  N    normalized normal vector
- * @param[in]  eta  ratio of indices of refraction
- * @returns refraction result
+ * @param[in]  eta  ratio of indices of refraction (incident/transmitted)
+ * @param[out] dest refraction vector if refraction occurs; zero vector otherwise
+ *
+ * @returns true if refraction occurs; false if total internal reflection occurs.
  */
 CGLM_INLINE
-vec4s
-glms_vec4_(refract)(vec4s I, vec4s N, float eta) {
-  vec4s dest;
-  glm_vec4_refract(I.raw, N.raw, eta, dest.raw);
-  return dest;
+bool
+glms_vec4_(refract)(vec4s I, vec4s N, float eta, vec4s * __restrict dest) {
+  return glm_vec4_refract(I.raw, N.raw, eta, dest->raw);
 }
 
 #endif /* cglms_vec4s_h */

include/cglm/vec2.h

@@ -729,18 +729,21 @@ glm_vec2_reflect(vec2 I, vec2 N, vec2 dest) {
 }
 
 /*!
- * @brief refraction vector using entering ray, surface normal and refraction index
+ * @brief computes refraction vector for an incident vector and a surface normal.
  *
- * if the angle between the entering ray I and the surface normal N is too great
- * for a given refraction index, the return value is zero
+ * calculates the refraction vector based on Snell's law. If total internal reflection
+ * occurs (angle too great given eta), dest is set to zero and returns false.
+ * Otherwise, computes refraction vector, stores it in dest, and returns true.
  *
  * @param[in]  I    normalized incident vector
  * @param[in]  N    normalized normal vector
- * @param[in]  eta  ratio of indices of refraction
- * @param[out] dest refraction result
+ * @param[in]  eta  ratio of indices of refraction (incident/transmitted)
+ * @param[out] dest refraction vector if refraction occurs; zero vector otherwise
+ *
+ * @returns true if refraction occurs; false if total internal reflection occurs.
  */
 CGLM_INLINE
-void 
+bool
 glm_vec2_refract(vec2 I, vec2 N, float eta, vec2 dest) {
   float ndi, eni, k;
 
@@ -750,11 +753,12 @@ glm_vec2_refract(vec2 I, vec2 N, float eta, vec2 dest) {
 
   if (k < 0.0f) {
     glm_vec2_zero(dest);
-    return;
+    return false;
   }
 
   glm_vec2_scale(I, eta, dest);
   glm_vec2_mulsubs(N, eni + sqrtf(k), dest);
+  return true;
 }
 
 #endif /* cglm_vec2_h */

include/cglm/vec3.h

@@ -1243,18 +1243,21 @@ glm_vec3_reflect(vec3 I, vec3 N, vec3 dest) {
 }
 
 /*!
- * @brief refraction vector using entering ray, surface normal and refraction index
+ * @brief computes refraction vector for an incident vector and a surface normal.
  *
- * if the angle between the entering ray I and the surface normal N is too great
- * for a given refraction index, the return value is zero
+ * calculates the refraction vector based on Snell's law. If total internal reflection
+ * occurs (angle too great given eta), dest is set to zero and returns false.
+ * Otherwise, computes refraction vector, stores it in dest, and returns true.
  *
  * @param[in]  I    normalized incident vector
  * @param[in]  N    normalized normal vector
- * @param[in]  eta  ratio of indices of refraction
- * @param[out] dest refraction result
+ * @param[in]  eta  ratio of indices of refraction (incident/transmitted)
+ * @param[out] dest refraction vector if refraction occurs; zero vector otherwise
+ *
+ * @returns true if refraction occurs; false if total internal reflection occurs.
  */
 CGLM_INLINE
-void
+bool
 glm_vec3_refract(vec3 I, vec3 N, float eta, vec3 dest) {
   float ndi, eni, k;
 
@@ -1264,11 +1267,12 @@ glm_vec3_refract(vec3 I, vec3 N, float eta, vec3 dest) {
 
   if (k < 0.0f) {
     glm_vec3_zero(dest);
-    return;
+    return false;
   }
 
   glm_vec3_scale(I, eta, dest);
   glm_vec3_mulsubs(N, eni + sqrtf(k), dest);
+  return true;
 }
 
 #endif /* cglm_vec3_h */

include/cglm/vec4.h

@@ -1326,10 +1326,11 @@ glm_vec4_reflect(vec4 I, vec4 N, vec4 dest) {
 }
 
 /*!
- * @brief refraction vector using entering ray, surface normal and refraction index
+ * @brief computes refraction vector for an incident vector and a surface normal.
  *
- * if the angle between the entering ray I and the surface normal N is too great
- * for a given refraction index, the return value is zero
+ * calculates the refraction vector based on Snell's law. If total internal reflection
+ * occurs (angle too great given eta), dest is set to zero and returns false.
+ * Otherwise, computes refraction vector, stores it in dest, and returns true.
  *
  * this implementation does not explicitly preserve the 'w' component of the
  * incident vector 'I' in the output 'dest', users requiring the preservation of
@@ -1337,11 +1338,13 @@ glm_vec4_reflect(vec4 I, vec4 N, vec4 dest) {
  *
  * @param[in]  I    normalized incident vector
  * @param[in]  N    normalized normal vector
- * @param[in]  eta  ratio of indices of refraction
- * @param[out] dest refraction result
+ * @param[in]  eta  ratio of indices of refraction (incident/transmitted)
+ * @param[out] dest refraction vector if refraction occurs; zero vector otherwise
+ *
+ * @returns true if refraction occurs; false if total internal reflection occurs.
  */
 CGLM_INLINE
-void 
+bool
 glm_vec4_refract(vec4 I, vec4 N, float eta, vec4 dest) {
   float ndi, eni, k;
 
@@ -1351,11 +1354,12 @@ glm_vec4_refract(vec4 I, vec4 N, float eta, vec4 dest) {
 
   if (k < 0.0f) {
     glm_vec4_zero(dest);
-    return;
+    return false;
   }
 
   glm_vec4_scale(I, eta, dest);
   glm_vec4_mulsubs(N, eni + sqrtf(k), dest);
+  return true;
 }
 
 #endif /* cglm_vec4_h */