From 4f951ffd8e368e4bc20fbd1fae84da59a86e00a8 Mon Sep 17 00:00:00 2001
From: gm-matthew <108370479+gm-matthew@users.noreply.github.com>
Date: Mon, 27 Oct 2025 12:47:31 +0000
Subject: [PATCH] sega/model2: fix textured mesh polygons

Need to double all the increment values
---
 src/mame/sega/model2rd.ipp | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/mame/sega/model2rd.ipp b/src/mame/sega/model2rd.ipp
index 6f0887ca17671..233a0707e7996 100644
--- a/src/mame/sega/model2rd.ipp
+++ b/src/mame/sega/model2rd.ipp
@@ -178,9 +178,16 @@ void model2_renderer::draw_scanline_tex(int32_t scanline, const extent_t &extent
 	colortable_b += ((colorbase >> 10) & 0x1f) << 8;
 
 	int x = extent.startx;
-	int dx = checker ? 2 : 1;
-	if (checker && !((x ^ scanline) & 1))
-		x++;
+	int dx = 1;
+	if (checker)
+	{
+		// if the first pixel is transparent, skip to the next one
+		if (!((x ^ scanline) & 1))
+			x++, ooz += dooz, uoz += dudxoz, voz += dvdxoz;
+
+		// increment by 2 pixels each time, skipping every other pixel
+		dx = 2, dooz *= 2.0f, dudxoz *= 2.0f, dvdxoz *= 2.0f;
+	}
 
 	for (; x < extent.stopx; x += dx, uoz += dudxoz, voz += dvdxoz, ooz += dooz)
 	{