View Full Version : dirtmap and alpha. HELP.

09 September 2004, 07:52 AM
Ok I (in fact, we) have got a little problem with the dirtmap. It has a really cool effect for what we do...but it destroy the alpha channel of the image, preferring using the luminance, that the real alpha.
Is there a way to change it in the dirtmap property ??
The dirtmap is a node connect to the camera, so is there a way to have the alpha not affect by the dirtmap in the render tree ( I don't to have to render an special alpha pass which will give us too much compositing work )

09 September 2004, 08:00 AM
What do you mean exactly by it destroys the alpha? You mean the alpha turns white? If so, try connecting your dirtmap shader in transparency.


09 September 2004, 09:19 AM
Ok we find the solution. In fact the dirtmap was mix with the "classical" color in a complicated way. So we find how take the alpha of the image and disable it to the dirtmap.

Anyway. Thanks Bernard.

09 September 2004, 12:30 PM
Maybe you can share your solution , it's a good place here for that.



09 September 2004, 01:34 PM
Ok an image of the render tree will make it clearer

The toon node is the "classical" render (necessary with dirtmap). We plug it with the dirtmap in the mix2color (official method for the dirtmap). Then to have a good aplha despite the mix method in the mix2colors we transform the alpha of the toon as his color with the pick channel node. Then we plug it in the color2alpha to adjust the weight of the dirtmap and then plug it in the weight panel. And so the dirtmap is no use for alpha black and use at the weight of the color 2alpha in the other part of the picture.
It's a little complicated to explain but it works

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