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| A subtle but important point in CS6 with ray tracing is to distinguish between Opacity and Transparency. Opacity alters the alpha channel for a layer; Transparency does not. If you create some extruded text in an otherwise blank comp, and either move the cursor across it while watching the RGBA values in the Info panel (or simply toggle on the Transparency Grid), you'll observe that a fully-transparent object with Opacity = 100% has an alpha value of 100% and does not pass the transparency grid through. Now, an admittedly confusing (but often desirable) quirk in CS6 is that if you place a 2D layer behind this transparent 3D layer _inside the same composition_, you can "look through" the transparent-but-opaque 3D layer and see the 2D layer. (It won't be refracted - only 3D layers get refracted by other 3D layers - but you'll see it.) So if you want to create a transparent object in AE, and render with an alpha that represents this "transparency", you'll need to fake it. What I used to do in dedicated 3D programs (which often have the same quirk) is render a second alpha-only pass and reduce the opacity of the semi-transparent objects just for that pass. You might get a better fake by placing a black solid behind, rendering the RGB, and converting that RGB pass into a grayscale alpha channel; this will show the effects of Transparency Rolloff. But I agree that it would be a nice feature request for AE to allow exporting of an alpha channel that matches what it does internally if there is a 2D layer behind in the same composition. In the meantime, think of it as being like exporting a layer with a blending mode: The blending mode only interacts with layers inside the same composition; not with layers composited outside the program. hope that helps - Chris On Jul 20, 2012, at 8:31 AM, mylenium@mylenium.de wrote:
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