From f743b2266198622823163cb6fcfe2c1582287206 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Fri, 3 Jan 2020 18:09:05 +0100
Subject: [PATCH] - render voxels as triangles instead of quads.

Quads are not available in the core profile which is required to run GL 3.3 on macOS.
---
 source/build/src/voxmodel.cpp  | 12 +++++++-----
 source/glbackend/glbackend.cpp |  1 -
 source/glbackend/glbackend.h   |  1 -
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/source/build/src/voxmodel.cpp b/source/build/src/voxmodel.cpp
index 7d666a214..1452c263d 100644
--- a/source/build/src/voxmodel.cpp
+++ b/source/build/src/voxmodel.cpp
@@ -1137,7 +1137,7 @@ int32_t polymost_voxdraw(voxmodel_t *m, tspriteptr_t const tspr)
 	GLInterface.UseDetailMapping(false);
 #endif
 
-	auto data = GLInterface.AllocVertices(m->qcnt * 4);
+	auto data = GLInterface.AllocVertices(m->qcnt * 6);
 	auto vt = data.second;
 
 	int qstart = 0;
@@ -1149,8 +1149,8 @@ int32_t polymost_voxdraw(voxmodel_t *m, tspriteptr_t const tspr)
             f = 1 /*clut[fi++]*/;
 			if (qdone > 0)
 			{
-				GLInterface.Draw(DT_QUADS, qstart, qdone * 4);
-				qstart += qdone * 4;
+				GLInterface.Draw(DT_TRIANGLES, qstart, qdone * 6);
+				qstart += qdone * 6;
 				qdone = 0;
 			}
             GLInterface.SetColor(pc[0]*f, pc[1]*f, pc[2]*f, pc[3]*f);
@@ -1162,8 +1162,10 @@ int32_t polymost_voxdraw(voxmodel_t *m, tspriteptr_t const tspr)
         const int32_t yy = vptr[0].y + vptr[2].y;
         const int32_t zz = vptr[0].z + vptr[2].z;
 
-        for (bssize_t j=0; j<4; j++, vt++)
+        for (bssize_t jj=0; jj<6; jj++, vt++)
         {
+            static uint8_t trix[] = { 0, 1, 2, 0, 2, 3 };
+            int j = trix[jj];
 #if (VOXBORDWIDTH == 0)
 			vt->SetTexCoord(((float)vptr[j].u)*ru + uhack[vptr[j].u!=vptr[0].u],
                           ((float)vptr[j].v)*rv + vhack[vptr[j].v!=vptr[0].v]);
@@ -1177,7 +1179,7 @@ int32_t polymost_voxdraw(voxmodel_t *m, tspriteptr_t const tspr)
 		qdone++;
     }
 
-	GLInterface.Draw(DT_QUADS, qstart, qdone * 4);
+	GLInterface.Draw(DT_TRIANGLES, qstart, qdone * 6);
 	GLInterface.SetClamp(prevClamp);
     //------------
 	GLInterface.SetCull(Cull_None);
diff --git a/source/glbackend/glbackend.cpp b/source/glbackend/glbackend.cpp
index 69f8e4525..da80b54fb 100644
--- a/source/glbackend/glbackend.cpp
+++ b/source/glbackend/glbackend.cpp
@@ -225,7 +225,6 @@ static GLint primtypes[] =
 	GL_TRIANGLES,
 	GL_TRIANGLE_STRIP,
 	GL_TRIANGLE_FAN,
-	GL_QUADS,
 	GL_LINES
 };
 	
diff --git a/source/glbackend/glbackend.h b/source/glbackend/glbackend.h
index ba5415efc..0625e668d 100644
--- a/source/glbackend/glbackend.h
+++ b/source/glbackend/glbackend.h
@@ -128,7 +128,6 @@ enum EDrawType
 	DT_TRIANGLES,
 	DT_TRIANGLE_STRIP,
 	DT_TRIANGLE_FAN,
-	DT_QUADS,
 	DT_LINES
 };