- Fix pixel center sampling bug in SWCanvas::DrawTexture

src/swrenderer/r_swcanvas.cpp

@@ -128,7 +128,7 @@ void SWCanvas::DrawTexture(DCanvas *canvas, FTexture *img, DrawParms &parms)
 		// There is not enough precision in the drawing routines to keep the full
 		// precision for y0. :(
 		double sprtopscreen;
-		modf(y0, &sprtopscreen);
+		modf(y0 + 0.5, &sprtopscreen);
 
 		double yscale = parms.destheight / img->GetHeight();
 		double iyscale = 1 / yscale;
@@ -192,6 +192,8 @@ void SWCanvas::DrawTexture(DCanvas *canvas, FTexture *img, DrawParms &parms)
 		int x2_i = int(x2);
 		fixed_t xiscale_i = FLOAT2FIXED(xiscale);
 
+		frac += xiscale_i / 2;
+
 		while (x < x2_i)
 		{
 			drawerargs.DrawMaskedColumn(&thread, x, iscale, img, frac, spryscale, sprtopscreen, sprflipvert, mfloorclip, mceilingclip, !parms.masked);