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dr_bob
05-26-2002, 04:17 PM
Hi

I'm trying to apply a non-rectangular label to a bottle in Maya.

I've created a label in Photoshop - with an alpha channel - and applied this texture to the colour channel of a blinn material.

In the hypershade, I've connected the outAlpha of the image file to the RGB transparency of the blinn material - this uses the alpha to cut out the portions of the label I don't want to see.

If I now apply this material to the bottle, the alpha acts as expected. So far so good. The problem arises if I resize the label on the bottle - the alpha does NOT resize, resulting in the color map and the alpha getting out of sync.

Does anyone have any suggestions as to how I can force the alpha channel to resize with the RGB channels? I would have thought this would happen automatically, given that the alpha and colour channels are parts of the same file, but apparently not.

Thanks in advance.
svenip
05-26-2002, 04:27 PM
uhh that sounds strange. but there seems to be always a problem in using this technique with an inside alpha. make the alpha map just as an extra image and apply then nothing strange will happen. also you can apply the same alpha map to the specular color if you wanna make objects with a shader different to lambert transparent.

did you used projections ??
dr_bob
05-26-2002, 04:32 PM
Originally posted by svenip


did you used projections ??

Yes, I was using planar projection.
svenip
05-26-2002, 04:50 PM
then actually the problem is clear. the shader gets the color not directly from the file. he gets the color from the projection. if you now connect the out_alpha of the texture directly to the shader you don't go with the projection. you just created a UV Mapping (standard if you just put the file to the color swatch).

so you really need to save the alpha to a seperate file and then create another projection for the transparency. you can easily do a connection from the color-projection to the transparency-projection then. go into the connection editor and connect the rotate/translate/and scale. now you can always be sure that the projection of the transparency follows the projection of the color.
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