Render Pass Tutorial

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In the tutorial, I showed how to render with alpha channels, however because I’m showing how to composite online, I have to use jpegs (which do not allow an alpha channel, targa files won’t display online).

So here is how to composite:

You may use any compositing program for this.  Basically, it’s just a matter of changing the blending modes.  You can use photoshop if you are compositing just a still image.  If you use photoshop you will need to open the channels panel, ctrl + click on the alpha channel for the ball, go to Selection>Inverse Selection and then press delete.  This will delete everything except for your object.

For any other compositing program (I used Combustion), you won’t need to do anything with the alpha channel.

First step:

Import all your images into your compositing program.  Layer them like this:

1st Layer - ballPassSpecular

- file name: ballPassSpecular.tga -blend mode: Add/Linear Dodge (Add)/Screen

2nd Layer - ballPassDiffuse

- file name: ballPassDiffuse.tga -blend mode: Normal

3rd Layer - setPassShadow

- file name: setPassShadows.tga -blend mode: Difference

4th Layer - setPassReflection

- file name: setPassReflection.tga -blend mode: Add/Linear Dodge (Add)/Screen

5th Layer - setPassDiffuseNoShadow

- file name: setPassDiffuse.tga -blend mode: Normal

End Result

You should end with something like the above image.

Keep in mind that there are many different ways that you can create render passes.  This is just a nice, quick, and easy way to do it.