From dda43d0adc1fb7323a6578f61565275694364bbd Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Fri, 9 Jul 2010 20:18:25 -0600
Subject: Save some degeneracy tests in ray-AABB intersection tests.

---
 libdimension/prtree.c | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

(limited to 'libdimension/prtree.c')

diff --git a/libdimension/prtree.c b/libdimension/prtree.c
index 04e7de9..e950917 100644
--- a/libdimension/prtree.c
+++ b/libdimension/prtree.c
@@ -529,7 +529,11 @@ dmnsn_ray_box_intersection(dmnsn_line line, dmnsn_bounding_box box, double t)
 {
   double tmin = -INFINITY, tmax = INFINITY;
 
-  if (line.n.x != 0.0 && box.min.x < box.max.x) {
+  /* Detenerate box test */
+  if (box.min.x >= box.max.x)
+    return false;
+
+  if (line.n.x != 0.0) {
     double tx1 = (box.min.x - line.x0.x)/line.n.x;
     double tx2 = (box.max.x - line.x0.x)/line.n.x;
 
@@ -538,12 +542,11 @@ dmnsn_ray_box_intersection(dmnsn_line line, dmnsn_bounding_box box, double t)
 
     if (tmin > tmax)
       return false;
-  } else {
-    if (line.x0.x < box.min.x || line.x0.x > box.max.x)
-      return false;
+  } else if (line.x0.x < box.min.x || line.x0.x > box.max.x) {
+    return false;
   }
 
-  if (line.n.y != 0.0 && box.min.y < box.max.y) {
+  if (line.n.y != 0.0) {
     double ty1 = (box.min.y - line.x0.y)/line.n.y;
     double ty2 = (box.max.y - line.x0.y)/line.n.y;
 
@@ -552,12 +555,11 @@ dmnsn_ray_box_intersection(dmnsn_line line, dmnsn_bounding_box box, double t)
 
     if (tmin > tmax)
       return false;
-  } else {
-    if (line.x0.y < box.min.y || line.x0.y > box.max.y)
-      return false;
+  } else if (line.x0.y < box.min.y || line.x0.y > box.max.y) {
+    return false;
   }
 
-  if (line.n.z != 0.0 && box.min.z < box.max.z) {
+  if (line.n.z != 0.0) {
     double tz1 = (box.min.z - line.x0.z)/line.n.z;
     double tz2 = (box.max.z - line.x0.z)/line.n.z;
 
@@ -566,15 +568,11 @@ dmnsn_ray_box_intersection(dmnsn_line line, dmnsn_bounding_box box, double t)
 
     if (tmin > tmax)
       return false;
-  } else {
-    if (line.x0.z < box.min.z || line.x0.z > box.max.z)
-      return false;
-  }
-
-  if (tmax < 0.0)
+  } else if (line.x0.z < box.min.z || line.x0.z > box.max.z) {
     return false;
+  }
 
-  return tmin < t;
+  return tmax >= 0.0 && tmin < t;
 }
 
 static void
-- 
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