From 9b2d36df0c9f71602e1ebc5f89cdbf4a7c3b2409 Mon Sep 17 00:00:00 2001
From: rogerman <rogerman@users.sf.net>
Date: Thu, 26 Mar 2015 09:49:56 +0000
Subject: [PATCH] GFX3D: - Do workaround for possible NaN comparisons being
 done when Y-sorting. (Addresses bug #1461.)

---
 desmume/src/gfx3d.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/desmume/src/gfx3d.cpp b/desmume/src/gfx3d.cpp
index 16ddf20d8..276a3bce2 100644
--- a/desmume/src/gfx3d.cpp
+++ b/desmume/src/gfx3d.cpp
@@ -2185,16 +2185,20 @@ static void gfx3d_doFlush()
 	//also the buttons in the knights in the nightmare frontend depend on this
 	for(int i=0; i<polycount; i++)
 	{
+		// TODO: Possible divide by zero with the w-coordinate.
+		// Is the vertex being read correctly? Is 0 a valid value for w?
+		// If both of these questions answer to yes, then how does the NDS handle a NaN?
+		// For now, simply prevent w from being zero.
 		POLY &poly = polylist->list[i];
 		float verty = vertlist->list[poly.vertIndexes[0]].y;
-		float vertw = vertlist->list[poly.vertIndexes[0]].w;
+		float vertw = (vertlist->list[poly.vertIndexes[0]].w != 0.0f) ? vertlist->list[poly.vertIndexes[0]].w : 0.00000001f;
 		verty = 1.0f-(verty+vertw)/(2*vertw);
 		poly.miny = poly.maxy = verty;
 
 		for(int j=1; j<poly.type; j++)
 		{
 			verty = vertlist->list[poly.vertIndexes[j]].y;
-			vertw = vertlist->list[poly.vertIndexes[j]].w;
+			vertw = (vertlist->list[poly.vertIndexes[j]].w != 0.0f) ? vertlist->list[poly.vertIndexes[j]].w : 0.00000001f;
 			verty = 1.0f-(verty+vertw)/(2*vertw);
 			poly.miny = min(poly.miny, verty);
 			poly.maxy = max(poly.maxy, verty);