View Full Version : strange alpha problem for mask

12-18-2005, 02:42 PM
hello, I've a strange problem

I've to do a render with tree as mask, and I can't have a correct alpha for the leaves
I don't know how to use a useBackground shader with an alpha to make a good mask.

So I use a trick, that I often use, but this time it make very strange result :
I use my black and white file to make the transparency of my shader (a simpe lambert)
then I set the mate opacity to zero.
so nothing special there....

but when I do a render here is what I have:
the color first

then the alpha

so the problem is that the alpha view is more contract.
but the file is ok , I test with all format, I redo my map 3 or 4 time....but it's wrong every time...
I don't use an alpha to make the transparency but juste the inverted color of the map
a screenShoot (http://homepage.mac.com/icevalley/.Pictures/Photo%20Album%20Pictures/2005-12-18%2006.54.58%20-0800/Image-AADA71106FD511DA.jpg)
so the transparency must be the same of the color....just?

the more funny thing is when I make a farest render, the color still ok but the alpha disappear

here is an exemple:

and alpha

I never had something like that and don't know what is the problem.

somebody have an idea where the problem come from, or already have this problem?
moreover is someone know how to use a useBackground shader with an alpha mask?

thanks in advance ;)

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12-18-2005, 02:42 PM
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