Integrating 2D and 3D

trythil · Post by **trythil** » Sat Jun 07, 2003 5:08 pm

Here's a nice sticky situation.

Ripped DVDs are at 29.97fps. 3D animation generated from Blender and POV-RAY runs at nfps, where n is some integer between 0 and infinity. I would like to have 23.976fps (online distribution) and 29.97fps (everything else) renders as targets.

What's the best way to integrate these two?

Here's two ideas that I've been experimenting with:

Generate the 3D at 24fps, telecine it up to 29.97fps, dump that in a 29.97fps timeline, do all the voodoo in there and then do time base correction to go from 29.97fps interlaced -> 23.97fps pseudo-progressive. I know this keeps audio/video sync, but it's kind of messy, and quite easy to get lost in.

#2: Do all the 3D work at 30fps, reframe to 29.97fps, and then put that in the 29.97fps timeline. That would save me a bit of mess with the telecining, but I'm not sure what that would do to audio/video sync (it shouldn't affect anything as far as I know, but it's not like I know a lot about this stuff...)

I know people have been able to pull off 2D animation and original 3D animation before, so there's got to be an easy way to do this. Any other thoughts?

One condition -- I can't easily turn the DVDs into progressive footage pre-edit. (No AVISynth here.)

koronoru · Post by **koronoru** » Sat Jun 07, 2003 5:34 pm

I don't know Blender, but with POV-Ray I'd just do the rendering twice, with different numbers of frames, always doing the POV rendering at whatever frame rate the final video will be. The usual animation technique with pure POV-Ray is to define a "clock" variable that goes from 0 to 1, or over some other convenient range (I'd probably make it count seconds if I wanted to do a long, complicated animation). When you do the render, you tell POV-Ray how many frames you want, and it calculates the clock value for each one. It shouldn't be hard to use the same scene files to render at multiple frame rates. My latest video starts with about ten seconds of pure-POV animation; I only did render it at 23.976, but if I wanted to I could easily render it at 29.970 by just telling it to render more frames. Just like you don't define individual pixels in POV, you don't define individual frames; you define a model of the world that changes over time, and then when you do an animation rendering, it samples your model at the appropriate moments. (Add-on software might change this model; I've only worked with plain POV.)

If you want to do an interlaced version and get it really right, you could render 59.940 frames per second and use POV-Ray's "field rendering" option - because the second field of a frame is really supposed to be an image from 1/59.940 seconds later than the image in the first field. I'm not sure exactly what the output format is like when you use field rendering (is each frame half height? are the missing lines filled in with black? or what?) but whatever software you use to convert the sequence of images into video should be able to deal with it one way or another.

koronoru · Post by **koronoru** » Sat Jun 07, 2003 5:45 pm

Further to previous - I wouldn't bother trying to do the animation in a nice frame rate like 24 or 30 because I'm not counting frames by hand anyway; I'd render with POV-Ray directly to whichever wacky NTSC frame rate I was using. (In the case of Mothyre, that was 23.976.) Any kind of frame rate conversion is going to be yucky in some way, so why dink around with that when you can freely adjust the source frame rate?

AbsoluteDestiny · Post by **AbsoluteDestiny** » Sat Jun 07, 2003 5:57 pm

OK, trying to simplify it - you want to basically have your 3d at a fractional frame rate, right?

You could make your 3d at 2997 fps, keep every 50th frame and use each frame as a field to make it into pure interlaced 29.97fps footage

trythil · Post by **trythil** » Sat Jun 07, 2003 6:52 pm

AbsoluteDestiny wrote:OK, trying to simplify it - you want to basically have your 3d at a fractional frame rate, right?

You could make your 3d at 2997 fps, keep every 50th frame and use each frame as a field to make it into pure interlaced 29.97fps footage

I might actually have to try that, if nothing else works

Though, just for the hell of it, I rendered out a sequence at 24fps, loaded it into the editor, just bumped the framerate to 29.97fps, and somehow the thing kept perfect audio/video sync for all 700 frames of the animation. I don't know if this is some fluke, but it works...I guess

koronoru: I've actually been tinkering around with POV-RAY as a substitute for Blender's rendering engine, and I'm not quite sure how the Blender -> POV SDL translation works, because I've not gotten it to really work yet

Pure POV isn't too hard, as you've noted; it's just that I could never get the hang of trying to envision a whole scene in scene description language...I'm weak, I need visuals

the Black Monarch · Post by **the Black Monarch** » Mon Jun 09, 2003 5:34 am

I'd just export at 24 FPS... I dunno what this 23.976 bullshit is about...

Tab. · Post by **Tab.** » Mon Jun 09, 2003 12:34 pm

that's cause you're a moron

trythil · Post by **trythil** » Mon Jun 09, 2003 12:57 pm

the Black Monarch wrote:I'd just export at 24 FPS... I dunno what this 23.976 bullshit is about...

Most of us don't have the luxury to work from film, and that extra .024fps really does make a difference stretched out over 5000 frames.

alternatefutures · Post by **alternatefutures** » Mon Jun 09, 2003 3:54 pm

If you export your footage at 24fps and then edit it at 24fps the export of the completed video will synch correctly. That's what I did with Light of Day for reasons you're coming up against (and Bryce is very inflexible when it comes to framerates) and because Premiere 5.1, which I was using, only approximates 23.976 anyway (at least that's what the framerate options would seem to imply). I got to see it later exported to NTSC and it still synched, so I don't see forcing everything into 24fps to be much of a problem.

the Black Monarch · Post by **the Black Monarch** » Mon Jun 09, 2003 5:40 pm

trythil wrote:
the Black Monarch wrote:I'd just export at 24 FPS... I dunno what this 23.976 bullshit is about...
Most of us don't have the luxury to work from film, and that extra .024fps really does make a difference stretched out over 5000 frames.

AssumeFPS(24)

Unless you're trying to export an entire episode or something.