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View Full Version : From AE to Lightwave: Alpha channel is not my friend



Sebasvideo
01-07-2013, 05:17 AM
I'm trying to import a video or sequence into Lightwave that has an alpha channel from a mask done in After Effects CS6. First I exported it as a totally uncompressed RGB AVI (no codec) and it gave me a full black frame. I made sure RGB+Alpha was selected in the export module. Then I tried image sequences with other formats, TGA, TIFF and PNG, always making sure that RGB+Alpha was selected, and also tried other things, like straight unmatted and premultiplied matted. I also tried exporting as two sets, one just the alpha channel and one the RGB, to then open the compositing options and set the foreground image and foreground alpha to the two sets respectively. And while they appear in the small preview right there, what I see in camera view with VPR enabled is not what I intended.

This is a simple take of the front of my house, with the sky removed so I can put a sky made with Skytracer 2 as a background, and then a spaceship flying above my house (this is part of my learning experience-gotta make it fun). The exported images are fine, since they open in Photoshop and show the area I cut out as transparent. But when I load them in Lightwave as foreground and alpha they load, but the removed sky doesn't even show as all black. Instead, part of it shows as black, but only as a rectangle, down to the top of the house, then it shows the full picture, including some of the areas I cut out.

I think I tried every export option I could find, is there a specific way to do this? I googled this and I couldn't find anything, and the manual doesn't make it clear either for me.

Thanks,

Sebastian

short223
01-07-2013, 09:58 AM
Maybe try this; Don't use the foreground/ background method but make a plane that is the same proportionate dimensions as the video and surface the video to that (Luminosity at 100, Diffuse 0, turn off shadows for the geometry). Then on the transparency surface, map an instance of your image (in Image panel make a duplicate and change the setting to ALPHA only) and apply that to make the area above the sky invisible. Make sure the camera is perpendicular to the plane and the the skytracer results should show up behind.

BigHache
01-07-2013, 10:06 AM
What you see in VPR and what you get from say an F9 render are not always a 1:1 relationship. That could be a factor.

While there are compositing options in LW, from a production standpoint I don't think it makes sense to use them, especially in this example and especially if you have After Effects. Now you might say, "that's not what I asked and not the way I want to do it," I think this is similar to the argument of rendering movies out of LW versus images sequences. You can but you probably shouldn't. FWIW

Sebasvideo
01-07-2013, 06:11 PM
While there are compositing options in LW, from a production standpoint I don't think it makes sense to use them, especially in this example and especially if you have After Effects. Now you might say, "that's not what I asked and not the way I want to do it," I think this is similar to the argument of rendering movies out of LW versus images sequences. You can but you probably shouldn't. FWIW

No, actually I don't mind you telling me how it's normally done, I would prefer to stick to the standards. But I thought that the normal way was to do the compositing in Lightwave.

LW_Will
01-07-2013, 11:48 PM
There are several different ways to do this, but the easiest is to do the compositing in AFX.

There is no "correct" way to do it... there is only the way either you figure it out or someone tells you.

The background/foreground was used heavily in the early days of LW. That was when the was no After Effects, and Chalice was a gleam in a programmer's eye.

BTW, never ever use the AVI uncompressed output from AFX. Usually doesn't work (as you saw).

I usually come out if AFX with MP4/h.264 files. Good balance of small compression and speed. If I was worried about Alphas, I'd use PNG32, recompile in Premiere Pro or AFX.

And you do know never output Animation files from Lightwave, right? Only frames... (PNG32 as well...)

jeric_synergy
01-08-2013, 01:14 AM
AND, if one really expects useful help, posting a sample image in the format in question goes a long way.

This thread made me learn that LightWave 3D predates AE by three years! Color me surprised!

djwaterman
01-08-2013, 02:20 AM
If your already using AE, then do the final composite there as well, so in LW you only need the house sequence as a background reference to line your shot up for generating your sky and spaceship against. Then those rendered sequences would be exported into AE for final composite. That's the normal way, yes you could do it all in LW but you can't really experiment with the fast feed back and massaging of elements like in AE. Learning some good basics of compositing will also bring about the understanding of just how much you can get away with in your 3D renders, good luck with it.