View Full Version : Compositing Transparent Objects from LW

08 August 2005, 01:34 AM
Okay, in my latest project I thought I could composite renders from LW of transparent objects into a previously rendered background sequence, but I found that the transparency had no where near the same crisp look as when the object and background were rendered together straight out of LW.

So, what methods are used to seamlessly composite foreground LW renders that include transparencies into a background as though they had been rendered together in first place?


08 August 2005, 01:36 PM

Some stuff just never works as well because of reflections and refractions that can only happen because the elements are "seeing" eachother in the scene.

I'm no expert but, when I composite stuff in After Effects, the 1st thing that I do is put the transparent image in a layer on top of the background with a "transfer mode" applied. "Add" usually works well, though "soft light" can give a more subtle result. Try others and see what looks best.

The other thing that can affect the compositing is the way you specify the Alpha channel to be used. Switching between "straight (unmatted)" or "premultiplied with color" can give dramatically different results. "Ignore" can also work with the "add" transfer mode depending on the footage.

I'm sure that there are multipass rendering methods that work even better.

When all is said and done, rendering it all together is the most foolproof way. :)

08 August 2005, 07:14 PM
Alright, at one level it's a relief to know that it wasn't totally my lack of technique, but on the other hand, I had actually been using Photoshop on a couple images, instead of AE. So, I'll be checking out your suggestions on the transfer modes to see if I can get any closer to the appearance of a fully internal LW render.

I guess there are other apps out there that work the "multi pass" side of things. Any suggestions on that front? And why haven't I heard much about a plug-in that came out for just such an occasion a few months back.... unfortunately I forget the name, but it seemed rather advanced and was intially drawing raves, but went silent.


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08 August 2005, 07:14 PM
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