Revert "Avoid batching skybox and horizon lines"

This reverts commit fc1e8fb5.

src/hardware/hw_batching.c

@@ -78,9 +78,7 @@ void HWR_SetCurrentTexture(GLMipmap_t *texture)
 // render the polygon immediately.
 void HWR_ProcessPolygon(FSurfaceInfo *pSurf, FOutVector *pOutVerts, FUINT iNumPts, FBITFIELD PolyFlags, int shader, boolean horizonSpecial)
 {
-	// draw skybox and horizon lines immediately so they don't bloat the polygon buffer.
-	// this is important for performance since horizon lines are order-sensitive and can't easily be batched.
-	if (currently_batching && !(PolyFlags & PF_NoTexture) && !horizonSpecial)
+    if (currently_batching)
 	{
 		if (!pSurf)
 			I_Error("Got a null FSurfaceInfo in batching");// nulls should not come in the stuff that batching currently applies to
@@ -117,25 +115,36 @@ void HWR_ProcessPolygon(FSurfaceInfo *pSurf, FOutVector *pOutVerts, FUINT iNumPt
 		polygonArray[polygonArraySize].polyFlags = PolyFlags;
 		polygonArray[polygonArraySize].texture = current_texture;
 		polygonArray[polygonArraySize].shader = shader;
+		polygonArray[polygonArraySize].horizonSpecial = horizonSpecial;
+		// default to polygonArraySize so we don't lose order on horizon lines
+		// (yes, it's supposed to be negative, since we're sorting in that direction)
+		polygonArray[polygonArraySize].hash = -polygonArraySize;
 		polygonArraySize++;
 
-		// use FNV-1a to hash polygons for later sorting.
-		INT32 hash = 0x811c9dc5;
-#define DIGEST(h, x) h ^= (x); h *= 0x01000193
-		DIGEST(hash, current_texture->downloaded);
-		DIGEST(hash, PolyFlags);
-		DIGEST(hash, pSurf->PolyColor.rgba);
-		if (cv_glshaders.value && gl_shadersavailable)
+		if (!(PolyFlags & PF_NoTexture) && !horizonSpecial)
 		{
-			DIGEST(hash, shader);
-			DIGEST(hash, pSurf->TintColor.rgba);
-			DIGEST(hash, pSurf->FadeColor.rgba);
-			DIGEST(hash, pSurf->LightInfo.light_level);
-			DIGEST(hash, pSurf->LightInfo.fade_start);
-			DIGEST(hash, pSurf->LightInfo.fade_end);
-		}
+			// use FNV-1a to hash polygons for later sorting.
+			INT32 hash = 0x811c9dc5;
+#define DIGEST(h, x) h ^= (x); h *= 0x01000193
+			if (current_texture)
+			{
+				DIGEST(hash, current_texture->downloaded);
+			}
+			DIGEST(hash, PolyFlags);
+			DIGEST(hash, pSurf->PolyColor.rgba);
+			if (cv_glshaders.value && gl_shadersavailable)
+			{
+				DIGEST(hash, shader);
+				DIGEST(hash, pSurf->TintColor.rgba);
+				DIGEST(hash, pSurf->FadeColor.rgba);
+				DIGEST(hash, pSurf->LightInfo.light_level);
+				DIGEST(hash, pSurf->LightInfo.fade_start);
+				DIGEST(hash, pSurf->LightInfo.fade_end);
+			}
 #undef DIGEST
-		polygonArray[polygonArraySize-1].hash = hash;
+			// remove the sign bit to ensure that skybox and horizon line comes first.
+			polygonArray[polygonArraySize-1].hash = (hash & INT32_MAX);
+		}
 
 		memcpy(&unsortedVertexArray[unsortedVertexArraySize], pOutVerts, iNumPts * sizeof(FOutVector));
 		unsortedVertexArraySize += iNumPts;
@@ -230,7 +239,10 @@ void HWR_RenderBatches(void)
 		HWD.pfnSetShader(currentShader);
 	}
 
-	HWD.pfnSetTexture(currentTexture);
+	if (currentPolyFlags & PF_NoTexture)
+		currentTexture = NULL;
+    else
+	    HWD.pfnSetTexture(currentTexture);
 
 	while (1)// note: remember handling notexture polyflag as having texture number 0 (also in comparePolygons)
 	{
@@ -302,6 +314,8 @@ void HWR_RenderBatches(void)
 			nextTexture = polygonArray[nextIndex].texture;
 			nextPolyFlags = polygonArray[nextIndex].polyFlags;
 			nextSurfaceInfo = polygonArray[nextIndex].surf;
+			if (nextPolyFlags & PF_NoTexture)
+				nextTexture = 0;
 			if (currentShader != nextShader && cv_glshaders.value && gl_shadersavailable)
 			{
 				changeState = true;

src/hardware/hw_batching.h

@@ -24,6 +24,8 @@ typedef struct
 	FBITFIELD polyFlags;
 	GLMipmap_t *texture;
 	int shader;
+	// this tells batching that the plane belongs to a horizon line and must be drawn in correct order with the skywalls
+	boolean horizonSpecial;
 	INT32 hash;
 } PolygonArrayEntry;