View Full Version : Alpha channel help?

01-02-2010, 08:53 PM
I am having a devil of a time trying to get an image in photoshop, which has an alpha channel, to show up properly when I map it to a plan in Modeler.

What I would like to end up with is this design to appear to be floating in the air, without a rectangle around it (hence the alpha channel), and to play with its opacity, etc..

I need the design to appear to be sort of ghosty.

any suggestions about how best to do this? Formats, etc...

PSD, PNG are not working, nor is EPS, so I'm a little stumped.

thank you for any help!


01-02-2010, 09:50 PM
What you want to do sounds straightforward so a little stumped as to why it's not working. Not trying to dumb things down but:

1. Are you sure you have the image cut out properly in Pshop?
2. When you import your image are you instancing it in the Image Editor window and setting the instance to Alpha Channel Only?
3. You have the Alpha Channel Only instance applied to the transparency channel?

01-02-2010, 09:58 PM
You want the plane to be transparent according to the alpha? You'll want to add the image as a node then and plug its colour into the surface colour, and its alpha into a Math>Scalar>Invert> then plug that into transparency for the Surface.

LW uses alphas normally (in texture layers for example) to make the texture a decal, rather than automatically linking them to transparency like maya does.

01-04-2010, 09:26 PM
thank you guys...

yes, what I want is my art to be visible and the entire rest of the plane it's mapped to to be 100% invisible.

I am really pooped right now, but will try your suggestions first thing in the morning...

thank you


01-05-2010, 01:38 PM
OK...I think I finally have it working, fundamentally...

I got some of the procedural aspects wrong, but thanks to you both, I corrected my mistake.

thank you,


01-07-2010, 08:35 PM
I've been using the clip map technique for things such as this. Am I like old school here? You guys are talking nodes as stuff. Is this better than clip mapping?

01-07-2010, 08:38 PM
it's nothing more than, when you click on the "T" for a node, say, for transparency, you select blending mode>Alpha. then, it makes that object transparent with respect to the alpha channel in your art.


01-07-2010, 11:15 PM
Clip mapping is much faster to render, so it has its uses.

01-08-2010, 06:47 AM
OK, Gotcha. This would also eliminate the need for seperate alpha art since it is apart of the original Pshop artwork. Learn something old everyday!

01-08-2010, 07:15 AM
how is clip mapping done?



01-08-2010, 08:58 AM
Just select the object, hit 'p' for properties. Then go to the Render tab and then click on [T]. Add your texture or procedural setting and you're pretty much done.

01-08-2010, 09:12 AM
...and in so doing, you apply your clipping path to transparency, reflection, color..etc?


01-12-2010, 08:36 AM
Ok, so this issue is all solved and ready to go. However, I'm working on a project where I'm using upwards of 20 images in a single object and all of them need the alpha as well, and need to show in OpenGL. Is there any way to show both the color and alpha in OpenGL without instancing the image and setting it to Alpha Only? If I didn't need it to show in the viewport I would just use nodes but I cant seem to get nodes to show in the viewports.

Any ideas?

Mental note: *being able to group images in the Image Editor would be nice...*