From 26abbb2bdae701a6ba090e3156ff0411d0114cbb Mon Sep 17 00:00:00 2001
From: Dominic Masters <dominic@domsplace.com>
Date: Fri, 24 Feb 2023 23:52:58 -0800
Subject: [PATCH] Fixed? Normal calculation on 3D AABB

---
 src/dawn/physics/3d/Ray3D.cpp | 42 +++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 19 deletions(-)

diff --git a/src/dawn/physics/3d/Ray3D.cpp b/src/dawn/physics/3d/Ray3D.cpp
index 99c5bed8..75f7111e 100644
--- a/src/dawn/physics/3d/Ray3D.cpp
+++ b/src/dawn/physics/3d/Ray3D.cpp
@@ -70,7 +70,7 @@ bool_t Dawn::raytestTriangle(
   glm::vec3 n0 = glm::cross(edge0, c0);
   glm::vec3 n1 = glm::cross(edge1, c1);
   glm::vec3 n2 = glm::cross(edge2, c2);
-  if (glm::dot(n0, normal) >= 0 && glm::dot(n1, normal) >= 0 && glm::dot(n2, normal) >= 0) {
+  if(glm::dot(n0, normal) >= 0 && glm::dot(n1, normal) >= 0 && glm::dot(n2, normal) >= 0) {
     // If the intersection point is inside the triangle, set the hit point, normal and distance
     *hitPoint = intersectionPoint;
     *hitNormal = normal;
@@ -89,6 +89,10 @@ bool_t Dawn::raytestAABB(
   glm::vec3 *normal,
   float_t *distance
 ) {
+  assertNotNull(point);
+  assertNotNull(normal);
+  assertNotNull(distance);
+
   // Compute the inverse direction of the ray, for numerical stability
   glm::vec3 invDir(1.0f / ray.direction.x, 1.0f / ray.direction.y, 1.0f / ray.direction.z);
 
@@ -103,7 +107,7 @@ bool_t Dawn::raytestAABB(
   float tFar = glm::compMin(t2);
 
   // If tNear is greater than or equal to tFar, there is no intersection
-  if (tNear >= tFar) return false;
+  if(tNear >= tFar) return false;
 
   // If tFar is negative, the ray is pointing away from the box
   if(tFar < 0.0f) return false;
@@ -111,25 +115,25 @@ bool_t Dawn::raytestAABB(
   // Compute the hit point and normal
   glm::vec3 hitPoint = ray.origin + tNear * ray.direction;
 
-  if(point != nullptr) *point = hitPoint;
-  if(distance != nullptr) *distance = tNear;
-  if(normal != nullptr) {
-    if (hitPoint.x == box.min.x) {
-      *normal = glm::vec3(-1, 0, 0);
-    } else if (hitPoint.x == box.max.x) {
-      *normal = glm::vec3(1, 0, 0);
-    } else if (hitPoint.y == box.min.y) {
-      *normal = glm::vec3(0, -1, 0);
-    } else if (hitPoint.y == box.max.y) {
-      *normal = glm::vec3(0, 1, 0);
-    } else if (hitPoint.z == box.min.z) {
-      *normal = glm::vec3(0, 0, -1);
-    } else if (hitPoint.z == box.max.z) {
-      *normal = glm::vec3(0, 0, 1);
-    }
+  *point = hitPoint;
+  *distance = tNear;
+
+  // Small value to account for floating point imprecision
+  const float epsilon = 0.001f; 
+  if(std::abs(hitPoint.x - box.min.x) < epsilon) {
+    *normal = glm::vec3(-1, 0, 0);
+  } else if(std::abs(hitPoint.x - box.max.x) < epsilon) {
+    *normal = glm::vec3(1, 0, 0);
+  } else if(std::abs(hitPoint.y - box.min.y) < epsilon) {
+    *normal = glm::vec3(0, -1, 0);
+  } else if(std::abs(hitPoint.y - box.max.y) < epsilon) {
+    *normal = glm::vec3(0, 1, 0);
+  } else if(std::abs(hitPoint.z - box.min.z) < epsilon) {
+    *normal = glm::vec3(0, 0, -1);
+  } else if(std::abs(hitPoint.z - box.max.z) < epsilon) {
+    *normal = glm::vec3(0, 0, 1);
   }
 
-  // The ray intersects the box
   return true;
 }