View Full Version : UV with decal textures - howto?

11-10-2005, 08:06 AM
I'm texturing a character, and I wanted to use decal-like textures for the lips, tatoos, etc., but somehow, it's not so easy. The texture itself with alpha channel works fine, but I have strange sawtooth-like render errors on the border of the decal - UV (the decal texture has it's own UV, but is on the general skin surface). My second attempt was to use two UVs, one for the texture and one for the alpha channel, where the UV for the alpha channel is a copy of the texture UV, but includes more polygons / patches on the surface. This works better, but seen from some camera angles, there appear small black spots (just one pixel) on the skin.

what am I missing? Is there a tutorial somewhere that deal with this decal stuff? Or do I need to create a UV map + texture for the whole body (which sems excessive to me)?

thanks in advance.

11-10-2005, 08:27 AM
Be sure your texture have enough color pixel spreading under the alpha for the mipmaping and antialias. The color must spread arround. Same for discontinious UVs. Make sure there are spreading color pixels arround borders.
This colors must be as close as possible as the pixels border.
You can check as well if you don't have polygons island too close from borders of your texture. With texture mipmaping and antialias, the left border spread on the right border and the top border on the bottom border.

11-10-2005, 07:26 PM
Are you saying that only straight alpha will work for this application and premultiplied alpha will not?


11-11-2005, 12:57 AM
I use a weightmap as a alpha to block out the sawtooth pattern. You could also just select all of the polys that you left out of your UV and add it to the same UV map , shrink them to a little point and leave this spot of the UV transparent.

11-11-2005, 03:43 PM
Thanks guys. I'll consider that weightmap solution

11-11-2005, 05:29 PM
Here is a very simple sample of usual alpha mistake.
You will not have black pixels arround your decal with this technic.

11-11-2005, 05:45 PM
And whith a more complicated spreading alpha gradiant.