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Best way to test rendering transparency?
I am using Sony Vegas Pro 9 (Windows 7). I am attempting to produce a short clip of a block turning with a transparent background.
I have followed many pieces of advice from this forum and elsewhere – eg render to Quicktime animation 32bit colour, or to uncompressed AVI with Alpha Channel and OpenDML boxes checked, no Field Order etc.
I can verify that the transparency exists BEFORE rendering by placing another track with, say, a checkerboard under it. The block appears perfectly on top of the checkerboard.
Upon rendering (after deleting the checkerboard) the background turns black, and appears black in whatever player I try. I’ve also tried bringing the rendered .mov or .avi back into Vegas and when I do, the background is black, and only a small sliver of checkerboard appears above and below the black.
I’ve also tried a test using the text generators with transparent backgrounds, but they also come back in with a black background.
I would be grateful for any suggestions – including how to verify for certain that there is no transparency. (It’s difficult to tell the difference between a black background and whatever default background players are using to denote transparency.)
I’ve noticed a few others on this forum and elsewhere with what appears to be the same issue – could it be something to do with codecs (apologies if that sounds stupid, I don’t know enough about the subject)?
Many thanks in advance
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8 Replies
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The step that you’re missing is to right-click on the clip and select Properties.
Switch to the Media tab and change the Alpha channel tab to “Straight (unmatted)”.
If that one doesn’t work, there are two other options to try. -
Thank you, Mike. I’ve tried Straight (unmatted) and both the Premul options, which make a slight difference to how the block looks before rendering but don’t change what happens on rendering. In all cases the video comes back in with a black background.
Other things I’ve tried are rendering with an empty video track underneath, and rendering in avi using the Lagarith codec, but neither of those make a difference.
Many thanks for your response
Jenny
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Jenny, how are you creating the block clip?
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Hi Mike
It is a sequence of .png files (generated in Blender 3d).
When I view it in the timeline it looks perfect – the cube sits there on top of a grey and white checkerboard background. But it plays with a black background in the preview pane, unless I put another track underneath it.
Thank you again for your help, I really appreciate it. I wonder if there’s something weird about my setup, or if I am missing some file?
Regards
Jenny
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Jenny, I deal with animation files (mostly TGA) from our animation students so I know that this should work.
Your settings look like they should work which really puzzles me.
Does Blender have an alpha channel option for PNG files?
If yes, did you use it for your renders?
Can you post here or email me one frame from Blender so that I can try it.
My email is mkujbida at gmail dot com -
You should know better, Mike. Keep it here – this is interesting.
Steve Mann
MannMade Digital Video
http://www.mmdv.com -
Hello Mike
Yes, Blender does have an alpha channel option for PNG files which I did use for rendering this sequence. I will attempt to attach one of the pngs here (and in case that doesn’t work I will email you one too). Thank you again for kindly looking at this.
Regards
Jenny
1166_0008.png.zip -
Jenny, it worked here as expected in both Pro 8 and Pro 9.
I suspect that your confusion is when you drop it on a checkerboard background.
That background is also transparent so, without any video information on a lower track, it will always appear black.
You did plan to place the animation over top of something else, didn’t you?BTW, in case you weren’t aware of it, you can import all your animation frames as a single clip into Vegas.
File – Import, browse to the folder containing the animation frames, click on the first image in the sequence, click the “Open still image sequence” box at the bottom of the window, click “Open”, set any desired parameters in the box that comes up and click OK.
The animation is now a single file in your project media tab waiting to be used as desired.
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