From 48839a38a14a653c233693fa911348ce58d57167 Mon Sep 17 00:00:00 2001
From: Recep Aslantas <info@recp.me>
Date: Mon, 15 Jul 2024 12:41:23 +0300
Subject: [PATCH] fix refract

---
 include/cglm/vec2.h  | 2 +-
 include/cglm/vec3.h  | 2 +-
 include/cglm/vec4.h  | 2 +-
 test/src/test_vec2.h | 4 ++--
 test/src/test_vec3.h | 4 ++--
 test/src/test_vec4.h | 4 ++--
 6 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/cglm/vec2.h b/include/cglm/vec2.h
index aaac759f..98cd4df1 100644
--- a/include/cglm/vec2.h
+++ b/include/cglm/vec2.h
@@ -749,7 +749,7 @@ glm_vec2_refract(vec2 v, vec2 n, float eta, vec2 dest) {
 
   ndi = glm_vec2_dot(n, v);
   eni = eta * ndi;
-  k   = 1.0f + eta * eta - eni * eni;
+  k   = 1.0f - eta * eta + eni * eni;
 
   if (k < 0.0f) {
     glm_vec2_zero(dest);
diff --git a/include/cglm/vec3.h b/include/cglm/vec3.h
index be4029b4..e6a98984 100644
--- a/include/cglm/vec3.h
+++ b/include/cglm/vec3.h
@@ -1263,7 +1263,7 @@ glm_vec3_refract(vec3 v, vec3 n, float eta, vec3 dest) {
 
   ndi = glm_vec3_dot(n, v);
   eni = eta * ndi;
-  k   = 1.0f + eta * eta - eni * eni;
+  k   = 1.0f - eta * eta + eni * eni;
 
   if (k < 0.0f) {
     glm_vec3_zero(dest);
diff --git a/include/cglm/vec4.h b/include/cglm/vec4.h
index e24675fc..b259235a 100644
--- a/include/cglm/vec4.h
+++ b/include/cglm/vec4.h
@@ -1350,7 +1350,7 @@ glm_vec4_refract(vec4 v, vec4 n, float eta, vec4 dest) {
 
   ndi = glm_vec4_dot(n, v);
   eni = eta * ndi;
-  k   = 1.0f + eta * eta - eni * eni;
+  k   = 1.0f - eta * eta + eni * eni;
 
   if (k < 0.0f) {
     glm_vec4_zero(dest);
diff --git a/test/src/test_vec2.h b/test/src/test_vec2.h
index e7bfe884..966847b7 100644
--- a/test/src/test_vec2.h
+++ b/test/src/test_vec2.h
@@ -792,7 +792,7 @@ TEST_IMPL(GLM_PREFIX, vec2_refract) {
   r = GLM(vec2_refract)(v, N, eta, dest);
   // In 2D, we expect a similar bending behavior as in 3D, so we check dest[1]
   if (!(dest[0] == 0.0f && dest[1] == 0.0f)) {
-    ASSERT(dest[1] < -sqrtf(0.5f)); // Refracted ray bends away from the normal
+    ASSERT(dest[1] < -0.3f); // Refracted ray bends away from the normal
     ASSERT(r == true);
   } else {
     ASSERT(dest[0] == 0.0f && dest[1] == 0.0f); // Total internal reflection
@@ -809,7 +809,7 @@ TEST_IMPL(GLM_PREFIX, vec2_refract) {
   eta = 1.5f / 1.33f;
   r = GLM(vec2_refract)(v, N, eta, dest);
   ASSERT(r == true);
-  ASSERT(dest[1] < -sqrtf(0.5f)); // Expect bending towards the normal, less bending than air to glass
+  ASSERT(dest[1] < -0.6f); // Expect bending towards the normal, less bending than air to glass
 
   /* Diamond to Air (eta = 2.42 / 1.0) */
   eta = 2.42f / 1.0f;
diff --git a/test/src/test_vec3.h b/test/src/test_vec3.h
index 7c057f30..ac504739 100644
--- a/test/src/test_vec3.h
+++ b/test/src/test_vec3.h
@@ -1901,7 +1901,7 @@ TEST_IMPL(GLM_PREFIX, vec3_refract) {
   eta = 1.33f / 1.0f;
   r = GLM(vec3_refract)(v, N, eta, dest);
   if (!(dest[0] == 0.0f && dest[1] == 0.0f && dest[2] == 0.0f)) {
-    ASSERT(dest[1] < -sqrtf(0.5f));
+    ASSERT(dest[1] < -0.3f);
     ASSERT(r == true);
   } else {
     ASSERT(dest[0] == 0.0f && dest[1] == 0.0f && dest[2] == 0.0f);
@@ -1922,7 +1922,7 @@ TEST_IMPL(GLM_PREFIX, vec3_refract) {
 
   /* Expect bending towards the normal, less bending than air to glass */
   ASSERT(r == true);
-  ASSERT(dest[1] < -sqrtf(0.5f));
+  ASSERT(dest[1] < -0.6f);
 
   /* Diamond to Air (eta = 2.42 / 1.0) */
   eta = 2.42f / 1.0f;
diff --git a/test/src/test_vec4.h b/test/src/test_vec4.h
index 435c7005..90122f2d 100644
--- a/test/src/test_vec4.h
+++ b/test/src/test_vec4.h
@@ -1586,7 +1586,7 @@ TEST_IMPL(GLM_PREFIX, vec4_refract) {
   eta = 1.33f / 1.0f;
   r = GLM(vec4_refract)(v, N, eta, dest);
   if (!(dest[0] == 0.0f && dest[1] == 0.0f && dest[2] == 0.0f && dest[3] == 0.0f)) {
-    ASSERT(dest[1] < -sqrtf(0.5f));
+    ASSERT(dest[1] < -0.3f);
     ASSERT(r == true);
   } else {
     ASSERT(dest[0] == 0.0f && dest[1] == 0.0f && dest[2] == 0.0f && dest[3] == 0.0f);
@@ -1603,7 +1603,7 @@ TEST_IMPL(GLM_PREFIX, vec4_refract) {
   eta = 1.5f / 1.33f;
   r = GLM(vec4_refract)(v, N, eta, dest);
   ASSERT(r == true);
-  ASSERT(dest[1] < -sqrtf(0.5f)); // Expect bending towards the normal, less bending than air to glass
+  ASSERT(dest[1] < -0.6f); // Expect bending towards the normal, less bending than air to glass
 
   /* Diamond to Air (eta = 2.42 / 1.0) */
   eta = 2.42f / 1.0f;