From 649a57f188e8545977eb60b7576398232e5be09a Mon Sep 17 00:00:00 2001
From: SomaZ <17459161+SomaZ@users.noreply.github.com>
Date: Fri, 3 May 2024 22:00:24 +0200
Subject: [PATCH] [rend2] Fix vertex lit shaders with lightmap stage

---
 shared/rd-rend2/tr_shader.cpp | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/shared/rd-rend2/tr_shader.cpp b/shared/rd-rend2/tr_shader.cpp
index 309312fe6b..cce8e5dd61 100644
--- a/shared/rd-rend2/tr_shader.cpp
+++ b/shared/rd-rend2/tr_shader.cpp
@@ -3375,8 +3375,9 @@ static qboolean CollapseStagesToGLSL(void)
 			diffuse  = pStage;
 			parallax = qfalse;
 			lightmap = NULL;
+			vertexlit = qfalse;
 
-			// we have a diffuse map, find matching lightmap
+			// we have a diffuse map, find matching lightmap or vertex lit stage
 			for (j = i + 1; j < MAX_SHADER_STAGES; j++)
 			{
 				shaderStage_t *pStage2 = &stages[j];
@@ -3396,6 +3397,16 @@ static qboolean CollapseStagesToGLSL(void)
 					lightmaps[j] = NULL;
 					break;
 				}
+
+				if (pStage2->bundle[0].isLightmap &&
+					pStage2->bundle[0].image[0] == tr.whiteImage &&
+					pStage2->rgbGen == CGEN_EXACT_VERTEX)
+				{
+					int blendBits = pStage2->stateBits & (GLS_DSTBLEND_BITS | GLS_SRCBLEND_BITS);
+					if (blendBits == (GLS_DSTBLEND_SRC_COLOR | GLS_SRCBLEND_ZERO) ||
+						blendBits == (GLS_DSTBLEND_ZERO | GLS_SRCBLEND_DST_COLOR))
+						vertexlit = qtrue;
+				}
 			}
 
 			tcgen = qfalse;
@@ -3415,7 +3426,6 @@ static qboolean CollapseStagesToGLSL(void)
 				diffuselit = qtrue;
 			}
 
-			vertexlit = qfalse;
 			if (diffuse->rgbGen == CGEN_VERTEX_LIT || diffuse->rgbGen == CGEN_EXACT_VERTEX_LIT || diffuse->rgbGen == CGEN_VERTEX || diffuse->rgbGen == CGEN_EXACT_VERTEX)
 			{
 				vertexlit = qtrue;