Rendering fixes ahoy!

- Fix squished sky in Software 3P/4P
- Fix reversed sky in OpenGL Mirror Mode
- Fix MD2 culling in Mirror Mode

src/hardware/hw_main.c

@@ -5433,9 +5433,14 @@ static void HWR_DrawSkyBackground(player_t *player)
 	// The only time this will probably be an issue is when a sky wider than 1024 is used as a sky AND a regular wall texture
 
 	angle = (dup_viewangle + gr_xtoviewangle[0]);
-
 	dimensionmultiply = ((float)textures[skytexture]->width/256.0f);
 
+	if (atransform.mirror)
+	{
+		angle = InvAngle(angle);
+		dimensionmultiply *= -1;
+	}
+
 	v[0].sow = v[3].sow = ((float) angle / ((ANGLE_90-1)*dimensionmultiply));
 	v[2].sow = v[1].sow = (-1.0f/dimensionmultiply)+((float) angle / ((ANGLE_90-1)*dimensionmultiply));
 

src/hardware/hw_md2.c

@@ -1523,6 +1523,7 @@ void HWR_DrawMD2(gr_vissprite_t *spr)
 		finalscale *= FIXED_TO_FLOAT(spr->mobj->scale);
 
 		p.flip = atransform.flip;
+		p.mirror = atransform.mirror;
 
 		HWD.pfnDrawMD2i(buff, curr, durs, tics, next, &p, finalscale, flip, color);
 	}

src/hardware/r_opengl/r_opengl.c

@@ -1874,14 +1874,16 @@ static  void DrawMD2Ex(INT32 *gl_cmd_buffer, md2_frame_t *frame, INT32 duration,
 
 	pglEnable(GL_CULL_FACE);
 
-	// pos->flip is if the screen is flipped too
-	if (flipped != pos->flip) // If either are active, but not both, invert the model's culling
+	// flipped is if the object is flipped
+	// pos->flip is if the screen is flipped vertically
+	// pos->mirror is if the screen is flipped horizontally
+	// XOR all the flips together to figure out what culling to use!
 	{
-		pglCullFace(GL_FRONT);
-	}
-	else
-	{
-		pglCullFace(GL_BACK);
+		boolean reversecull = (flipped ^ pos->flip ^ pos->mirror);
+		if (reversecull)
+			pglCullFace(GL_FRONT);
+		else
+			pglCullFace(GL_BACK);
 	}
 
 #ifndef KOS_GL_COMPATIBILITY

src/r_sky.c

@@ -80,5 +80,8 @@ void R_SetupSkyDraw(void)
 void R_SetSkyScale(void)
 {
 	fixed_t difference = vid.fdupx-(vid.dupx<<FRACBITS);
-	skyscale = FixedDiv(FRACUNIT, vid.fdupx+difference);
+	fixed_t scr = FRACUNIT;
+	if (splitscreen > 1)
+		scr *= 2;
+	skyscale = FixedDiv(scr, vid.fdupx+difference);
 }