From 6ac852d45b3a53dc51414773454e6bae7126fe33 Mon Sep 17 00:00:00 2001
From: Brian Paul <brian.paul@tungstengraphics.com>
Date: Tue, 10 Apr 2001 15:46:51 +0000
Subject: fixed some divide by zero conformance problems

---
 src/mesa/swrast/s_aaline.c     | 27 +++++++++++++++++++--------
 src/mesa/swrast/s_aatriangle.c | 11 +++++++----
 2 files changed, 26 insertions(+), 12 deletions(-)

(limited to 'src/mesa')

diff --git a/src/mesa/swrast/s_aaline.c b/src/mesa/swrast/s_aaline.c
index 89df853233..f60233c3ac 100644
--- a/src/mesa/swrast/s_aaline.c
+++ b/src/mesa/swrast/s_aaline.c
@@ -1,4 +1,4 @@
-/* $Id: s_aaline.c,v 1.7 2001/03/28 21:37:24 brianp Exp $ */
+/* $Id: s_aaline.c,v 1.8 2001/04/10 15:46:51 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -120,10 +120,18 @@ compute_plane(GLfloat x0, GLfloat y0, GLfloat x1, GLfloat y1,
    const GLfloat b = pz * py;
    const GLfloat c = px * px + py * py;
    const GLfloat d = -(a * x0 + b * y0 + c * z0);
-   plane[0] = a;
-   plane[1] = b;
-   plane[2] = c;
-   plane[3] = d;
+   if (a == 0.0 && b == 0.0 && c == 0.0 && d == 0.0) {
+      plane[0] = 0.0;
+      plane[1] = 0.0;
+      plane[2] = 1.0;
+      plane[3] = 0.0;
+   }
+   else {
+      plane[0] = a;
+      plane[1] = b;
+      plane[2] = c;
+      plane[3] = d;
+   }
 #endif
 }
 
@@ -141,7 +149,7 @@ constant_plane(GLfloat value, GLfloat plane[4])
 static INLINE GLfloat
 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 {
-   GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
+   const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
    return z;
 }
 
@@ -155,8 +163,11 @@ solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 static INLINE GLfloat
 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 {
-   GLfloat z = -plane[2] / (plane[3] + plane[0] * x + plane[1] * y);
-   return z;
+   const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
+   if (denom == 0.0)
+      return 0.0;
+   else
+      return -plane[2] / denom;
 }
 
 
diff --git a/src/mesa/swrast/s_aatriangle.c b/src/mesa/swrast/s_aatriangle.c
index 93f65b826c..8235e957e3 100644
--- a/src/mesa/swrast/s_aatriangle.c
+++ b/src/mesa/swrast/s_aatriangle.c
@@ -1,4 +1,4 @@
-/* $Id: s_aatriangle.c,v 1.12 2001/03/29 16:50:32 brianp Exp $ */
+/* $Id: s_aatriangle.c,v 1.13 2001/04/10 15:46:51 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -92,7 +92,7 @@ do {					\
 static INLINE GLfloat
 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 {
-   GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
+   const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
    return z;
 }
 
@@ -107,8 +107,11 @@ solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 static INLINE GLfloat
 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 {
-   GLfloat z = -plane[2] / (plane[3] + plane[0] * x + plane[1] * y);
-   return z;
+   const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
+   if (denom == 0.0F)
+      return 0.0F;
+   else
+      return -plane[2] / denom;
 }
 
 
-- 
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