From 93f273bf840730931ce7afa1cb4e838d2f2b4eb9 Mon Sep 17 00:00:00 2001
From: Bigfoot71 <victor.lejuez@protonmail.ch>
Date: Sat, 18 Jul 2026 14:36:40 +0200
Subject: [PATCH] check whether vertex colors should be interpolated

---
 src/external/rlsw.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/external/rlsw.h b/src/external/rlsw.h
index 491e33996..c27fab8f9 100644
--- a/src/external/rlsw.h
+++ b/src/external/rlsw.h
@@ -3783,7 +3783,6 @@ static void sw_immediate_set_color(const float color[4])
     RLSW.primitive.color[1] = color[1];
     RLSW.primitive.color[2] = color[2];
     RLSW.primitive.color[3] = color[3];
-
 }
 
 static void sw_immediate_set_texcoord(const float texcoord[2])
@@ -3840,6 +3839,18 @@ static void sw_immediate_push_vertex(const float position[4])
             }
         }
 
+        // Determine whether colors should be interpolated
+        const float *ref = RLSW.primitive.buffer[0].color;
+        for (int i = 1; i < RLSW.primitive.vertexCount; ++i)
+        {
+            const float *c = RLSW.primitive.buffer[i].color;
+            if (c[0] != ref[0] || c[1] != ref[1] || c[2] != ref[2] || c[3] != ref[3])
+            {
+                state |= SW_STATE_COLOR_INTERP;
+                break;
+            }
+        }
+
         switch (RLSW.polyMode)
         {
             case SW_FILL: sw_poly_fill_render(state); break;