From 7a4ca89b14b98bc672d75ef76d905659073210dd Mon Sep 17 00:00:00 2001
From: Wellinator <wellcoj@gmail.com>
Date: Sun, 14 Aug 2022 16:52:06 -0300
Subject: [PATCH] refactor: implroves ray box collision accuracy

---
 engine/src/physics/ray.cpp | 55 +++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 27 deletions(-)

diff --git a/engine/src/physics/ray.cpp b/engine/src/physics/ray.cpp
index 6fafbaa..94430ab 100644
--- a/engine/src/physics/ray.cpp
+++ b/engine/src/physics/ray.cpp
@@ -33,41 +33,42 @@ float Ray::distanceToPoint(const Vec4& point) const {
 
 bool Ray::intersectBox(const Vec4& minCorner, const Vec4& maxCorner,
                        float* outputDistance) const {
-  auto inv = invDir();
-  inv.normalize();
+  float t1 = (min->x - origin->x) / dir->x;
+  float t2 = (max->x - origin->x) / dir->x;
+  float t3 = (min->y - origin->y) / dir->y;
+  float t4 = (max->y - origin->y) / dir->y;
+  float t5 = (min->z - origin->z) / dir->z;
+  float t6 = (max->z - origin->z) / dir->z;
 
-  float tmin = (minCorner.x - this->origin.x) * inv.x;
-  float tmax = (maxCorner.x - this->origin.x) * inv.x;
-  float tymin = (minCorner.y - this->origin.y) * inv.y;
-  float tymax = (maxCorner.y - this->origin.y) * inv.y;
-
-  if ((tmin > tymax) || (tymin > tmax)) {
-    return false;
-  }
-
-  if (tymin > tmin) tmin = tymin;
-
-  if (tymax < tmax) tmax = tymax;
-
-  float tzmin = (minCorner.z - this->origin.z) * inv.z;
-  float tzmax = (maxCorner.z - this->origin.z) * inv.z;
-
-  if ((tmin > tzmax) || (tzmin > tmax)) {
-    return false;
-  }
-
-  if (tzmin > tmin) tmin = tzmin;
-
-  if (tzmax < tmax) tmax = tzmax;
+  float tmin = MAX(MAX(MIN(t1, t2), MIN(t3, t4)), MIN(t5, t6));
+  float tmax = MIN(MIN(MAX(t1, t2), MAX(t3, t4)), MAX(t5, t6));
 
+  // if tmax < 0, ray (line) is intersecting AABB, but whole AABB is behing us
   if (tmax < 0) {
+    if (outputDistance != nullptr) {
+      *outputDistance = -1.0f;
+    }
     return false;
   }
 
+  // if tmin > tmax, ray doesn't intersect AABB
+  if (tmin > tmax) {
+    if (outputDistance != nullptr) {
+      *outputDistance = -1.0f;
+    }
+    return false;
+  }
+
+  if (tmin < 0) {
+    if (outputDistance != nullptr) {
+      *outputDistance = tmax;
+    }
+    return true;
+  }
+
   if (outputDistance != nullptr) {
-    *outputDistance = tmin >= 0 ? tmin : tmax;
+    *outputDistance = tmin;
   }
-
   return true;
 }