diff --git a/zscript/firetexture_m/ft_baseclass.zsc b/zscript/firetexture_m/ft_baseclass.zsc
index 0a60ea6..6917857 100644
--- a/zscript/firetexture_m/ft_baseclass.zsc
+++ b/zscript/firetexture_m/ft_baseclass.zsc
@@ -232,8 +232,8 @@ class FireTexture
 			// prepare the lut
 			for ( int i=0; i<256; i++ )
 			{
-				double x = pal[i].r+((pal[i].g/16)*256)%4096;
-				double y = (pal[i].g/16)+(pal[i].b*16);
+				double x = pal[i].r+((pal[i].g>>4)<<8)&4095;
+				double y = (pal[i].g>>4)+(pal[i].b<<4);
 				blitterlut[i] = (x,y)/4096.+(1.,1.)/8192.;
 			}
 		}
diff --git a/zscript/firetexture_m/ft_pixel.zsc b/zscript/firetexture_m/ft_pixel.zsc
index 625c443..d96705f 100644
--- a/zscript/firetexture_m/ft_pixel.zsc
+++ b/zscript/firetexture_m/ft_pixel.zsc
@@ -13,6 +13,7 @@ extend class FireTexture
 	private int renderheat;		// overall intensity
 
 	// direct pixel access wrapper functions
+	// not used by the Calc code, would reduce performance
 	private uint GetPixel( uint x, uint y )
 	{
 		// ensure coords are wrapped
@@ -27,33 +28,74 @@ extend class FireTexture
 		y &= vmask;
 		pixels[x+y*width] = c;
 	}
-	private Color GetPixelRGB( uint x, uint y )
-	{
-		// ensure coords are wrapped
-		x &= umask;
-		y &= vmask;
-		return pal[pixels[x+y*width]];
-	}
-
-	private uint LookupFiretable( uint a, uint b, uint c, uint d )
-	{
-		return firetable[min(a+b+c+d,1023)];
-	}
 
 	// heat propagation with bRising (triangle shifted two pixels down)
 	private void CalcWrapFire()
 	{
 		uint mid, left, right, up;
-		for ( uint y=0; y<height; y++ )
+		uint y;
+		for ( y=0; y<height-2; y++ )
 		{
-			for ( uint x=0; x<width; x++ )
+			mid = pixels[(y+1)*width];
+			left = pixels[(width-1)+(y+1)*width];
+			right = pixels[1+(y+1)*width];
+			up = pixels[(y+2)*width];
+			pixels[y*width] = firetable[mid+left+right+up];
+			for ( uint x=1; x<width-1; x++ )
 			{
-				mid = GetPixel(x,y+1);
-				left = GetPixel(x-1,y+1);
-				right = GetPixel(x+1,y+1);
-				up = GetPixel(x,y+2);
-				PutPixel(x,y,LookupFiretable(mid,left,right,up));
+				mid = pixels[x+(y+1)*width];
+				left = pixels[(x-1)+(y+1)*width];
+				right = pixels[(x+1)+(y+1)*width];
+				up = pixels[x+(y+2)*width];
+				pixels[x+y*width] = firetable[mid+left+right+up];
 			}
+			mid = pixels[(width-1)+(y+1)*width];
+			left = pixels[(width-2)+(y+1)*width];
+			right = pixels[(y+1)*width];
+			up = pixels[(width-1)+(y+2)*width];
+			pixels[(width-1)+y*width] = firetable[mid+left+right+up];
+		}
+		y = height-2;
+		{
+			mid = pixels[(y+1)*width];
+			left = pixels[(width-1)+(y+1)*width];
+			right = pixels[1+(y+1)*width];
+			up = pixels[0];
+			pixels[y*width] = firetable[mid+left+right+up];
+			for ( uint x=1; x<width-1; x++ )
+			{
+				mid = pixels[x+(y+1)*width];
+				left = pixels[(x-1)+(y+1)*width];
+				right = pixels[(x+1)+(y+1)*width];
+				up = pixels[x];
+				pixels[x+y*width] = firetable[mid+left+right+up];
+			}
+			mid = pixels[(width-1)+(y+1)*width];
+			left = pixels[(width-2)+(y+1)*width];
+			right = pixels[(y+1)*width];
+			up = pixels[(width-1)];
+			pixels[(width-1)+y*width] = firetable[mid+left+right+up];
+		}
+		y = height-1;
+		{
+			mid = pixels[width];
+			left = pixels[(width-1)];
+			right = pixels[1];
+			up = pixels[2*width];
+			pixels[y*width] = firetable[mid+left+right+up];
+			for ( uint x=1; x<width-1; x++ )
+			{
+				mid = pixels[x+width];
+				left = pixels[(x-1)+width];
+				right = pixels[(x+1)+width];
+				up = pixels[x+2*width];
+				pixels[x+y*width] = firetable[mid+left+right+up];
+			}
+			mid = pixels[(width-1)+width];
+			left = pixels[(width-2)+width];
+			right = pixels[width];
+			up = pixels[(width-1)+2*width];
+			pixels[(width-1)+y*width] = firetable[mid+left+right+up];
 		}
 	}
 	// ... without bRising (triangle shifted one pixel down)
@@ -64,16 +106,48 @@ extend class FireTexture
 		uint temp[256];
 		for ( uint i=0; i<width; i++ ) temp[i] = pixels[i];
 		uint mid, left, right, up;
-		for ( uint y=0; y<height; y++ )
+		uint y;
+		for ( y=0; y<height-1; y++ )
 		{
-			for ( uint x=0; x<width; x++ )
+			mid = pixels[y*width];
+			left = pixels[(width-1)+y*width];
+			right = pixels[1+y*width];
+			up = pixels[(y+1)*width];
+			pixels[y*width] = firetable[mid+left+right+up];
+			for ( uint x=1; x<width-1; x++ )
 			{
-				mid = GetPixel(x,y);
-				left = GetPixel(x-1,y);
-				right = GetPixel(x+1,y);
-				up = (y==height-1)?temp[x&255]:GetPixel(x,y+1);
-				PutPixel(x,y,LookupFiretable(mid,left,right,up));
+				mid = pixels[x+y*width];
+				left = pixels[(x-1)+y*width];
+				right = pixels[(x+1)+y*width];
+				up = pixels[x+(y+1)*width];
+				pixels[x+y*width] = firetable[mid+left+right+up];
 			}
+			mid = pixels[(width-1)+y*width];
+			left = pixels[(width-2)+y*width];
+			right = pixels[y*width];
+			up = pixels[(width-1)+(y+1)*width];
+			pixels[(width-1)+y*width] = firetable[mid+left+right+up];
+		}
+		y = height-1;
+		{
+			mid = pixels[y*width];
+			left = pixels[(width-1)+y*width];
+			right = pixels[1+y*width];
+			up = temp[0];
+			pixels[y*width] = firetable[mid+left+right+up];
+			for ( uint x=1; x<width-1; x++ )
+			{
+				mid = pixels[x+y*width];
+				left = pixels[(x-1)+y*width];
+				right = pixels[(x+1)+y*width];
+				up = temp[x];
+				pixels[x+y*width] = firetable[mid+left+right+up];
+			}
+			mid = pixels[(width-1)+y*width];
+			left = pixels[(width-2)+y*width];
+			right = pixels[y*width];
+			up = temp[width-1];
+			pixels[(width-1)+y*width] = firetable[mid+left+right+up];
 		}
 	}
 }