From 52d4c3970e3241a60a61dc5c304f8f425d14d9e2 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@zdoom.fake>
Date: Thu, 22 Sep 2016 10:00:40 +0200
Subject: [PATCH] - use glPOlygonOffset on non-translucent flat and wall
 sprites to avoid z-fighting.

---
 src/gl/scene/gl_sprite.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/gl/scene/gl_sprite.cpp b/src/gl/scene/gl_sprite.cpp
index 720df3b2b..123bf258c 100644
--- a/src/gl/scene/gl_sprite.cpp
+++ b/src/gl/scene/gl_sprite.cpp
@@ -310,6 +310,11 @@ void GLSprite::Draw(int pass)
 			additivefog = true;
 		}
 	}
+	else if (modelframe == nullptr)
+	{
+		glEnable(GL_POLYGON_OFFSET_FILL);
+		glPolygonOffset(-1.0f, -128.0f);
+	}
 	if (RenderStyle.BlendOp!=STYLEOP_Shadow)
 	{
 		if (gl_lights && GLRenderer->mLightCount && !gl_fixedcolormap && !fullbright)
@@ -440,6 +445,11 @@ void GLSprite::Draw(int pass)
 		gl_RenderState.BlendEquation(GL_FUNC_ADD);
 		gl_RenderState.SetTextureMode(TM_MODULATE);
 	}
+	else if (modelframe == nullptr)
+	{
+		glPolygonOffset(0.0f, 0.0f);
+		glDisable(GL_POLYGON_OFFSET_FILL);
+	}
 
 	gl_RenderState.SetObjectColor(0xffffffff);
 	gl_RenderState.EnableTexture(true);