Texture/material with one color transparent?

[Jox]

Hi,
How should I use a texture in Maya if I have a picture from which I'd like one color to be transparent when used as a material? Let's say an edited skyline-picture (applied to a plane), where I've edited the sky just one-color-blue. Or another example, a green plant which I've shoot against bluescreen, and would like to use as a 2D plane, with objects from the back shining thru. Any ideas on this?

[natalinow]

You need a transparency map. Having read your examples, I assume that you have a picture file. You've created a shader (e.g. Lambert1) and put the picture file in the color channel (with Lambert1 highlighted: Attribute Editor -> Common Material Attributes -> Color, klick on the checker button on the right: Create Render Node -> Textures -> 2D Textures -> File, back in the Attribute Editor with file1 highlighted: File Attributes -> Image Name -> your Image Path)

Since you want some parts of your plane to be transparent, you do the same thing for the transparency channel of your Shader (Lambert1). But instead of the image, you use its mask. Which is actually another image but in grayscale where white represents 100% transparency and black 0% transparency. So go back to Photoshop (or whatever you use), open your image (e.g. the skyline), make a new layer and select the sky (which you want to have transparent). Fill the selection on your new layer white, invert the selection and fill the rest black (since you don't want these parts to be transparent later on in Maya). You should now see a completely black&white; picture whith a white sky and a black skyline. Save this file with another name than your original and go back to Maya.

Back in Maya, highlight your shader in the Hypershade. Open the Attribute Editor and do the same as above except that you click on the checker button next to the transparency. After your done, don't forget to assign your shader to your plane. That should do the trick. It's not the most elegant method but it works.

[Jox]

Thanks for your help! That should solve my problem.

Now if I only could overcome this next problem of mine... I've set Maya6 to 25fps and render my scene in PAL-resolution, but
the resulting .avi-file is still 30fps video according to all other software?!
It causes great problems when compositing in After Effects, etc.
I will post this as a new message also.
Thanks once again, natalinow,
Jox

[natalinow]

It is not recommendable to let Maya render an avi. Sometimes there can be rendering mistakes: Maya renders a frame which is corrupt. When this happens in an avi file, the whole file i.e. your whole animation is for the birds. It happened to me once: the computer had rendered for 5 days and then it turned out that I could not open that st***p avi file! *Grrrrrr*

So it is always better to render single images (I mostly use .tif). Set the Frame/Animation Ext in the Render Globals Window to "name.#.ext" and let the computer render your animation sequence in single images. With this method, you can also distribute the rendering among several computers. Let them just render different sequences of your animation. Lateron, you import the whole load of images into Adobe Premiere (or whatever program you use) where you can decide on the frames per second and the other stuff.