alpha Question

[xvivo]

i have read through some threads on this topic, and i seem to be still missing something. I am trying to export an image from Zbrush with its corresponding alpha(transparency). It works.. kind of..but the alpha channel in photoshop is full of a seemingly random black and white texture..is there a setting i need to change? what am i doing wrong.

Thanks in advance

mike http://www2.zbrushcentral.com/zbc_uploads/user_image-1030706536ajg.jpg

[banez]

probley just like z brush but not sure but if you export a alpha threw alpha/export thats all you get is a black and white image.

[Mentat7]

That almost looks like it is exporting the alpha with UV Tiling coordinates. Try changing the UV coordinate settings TOOLS>MODIFIERS>TEXTURES

[aurick]

I think I spoke with you on the phone about this issue just this morning. :) But just to be safe, here's the scoop:

It looks like what you have here is an alpha that was grabbed from a painting rather than from 3D objects. As a result, you don't have very much depth variation for the MRGBZGrabber to work with, and the result is that even a slight change in depth becomes a massive change in color value.

For this type of export, you would be better off as a last step before exporting changing your background color. Choose any color that is not present in your picture, then click the Document>Modifiers>Back square. The background color will be changed to the new color. In Photoshop, duplicate the layer and delete the locked background layer. You would then use the Magic Wand to select that color. Enlarge your selection by 1 or 2 pixels to make sure that you've removed all traces of the background color. Feather it slightly if you want. Then press delete to remove the color.

Edit: More info (from "on high") that I just learned is that the alpha created by the MRGBZGrabber is a 16-bit image -- lots more color variations than Photoshop will recognize! Pressing the Alpha>Make TX button converts the alpha to an 8-bit texture, which may also do the trick for you. (thanks, Pixolator!)

For images with quite a bit of depth variation, then you would use the MRGBZGrabber and export both the image and the alpha grabs. The alpha can then be used as an alpha channel in Photoshop. However, you will find it useful to adjust the levels on the alpha in order to turn the gray values to white. Simply drag the right triangle below the histogram all the way to the left.

Hope that helps!

Here are some more links with info on the subject:

Thread 1 (http://www.pixolator.com/zbc-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=004062)
Thread 2 (http://www.pixolator.com/zbc-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=000214)
Thread 3 (http://www.pixolator.com/zbc-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=001531)