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View Full Version : Motion Baker: What's the frakking problem?!



WShawn
01-23-2006, 02:01 PM
Greetings:

I'm attempting to motion bake the motion of a null that has been parented to the camera to faciliate bringing the 3D camera data into After Effects using the Transmotion POI plugin. It's a scene which has the camera coming around the moon, flying towards Earth, pausing to show a satellite in orbit, then flying down towards the surface.

The null is parented 2Mm in front of the camera so it's always smack in the middle of the screen.

Here's the process. I select the motion options for the null and add the Motion Baker modifier. New Key Mode is set to Use Existing with the Position.X, Y, & Z enabled. As soon as I start to drag the time slider the null jumps 40Mm away from the camera. As I continue to drag, the null traces out a roughly pentagonal path with a 40Mm diameter, spiraling upwards. I've attached a screen grab showing the top view of the result.

I can't motion bake this in the graph editor because the null has no independent motion.

Any thoughts as to why this won't work? Any alternate solutions?

Here's the reason I'm trying to do this. I set up the above scene first and got it the way I wanted it to look. Once the camera flys towards the Earth I wanted to layer in some clouds to transition to 2D satellite images of a city. I originally was going to try to do the clouds in LW using hypervoxels but the renders were going to be interminable. I was able to create pretty good 3D clouds using the Particular plugin in After Effects, but I was having no success trying to match them to the dynamic camera move. I tried using RPF data to match the LW camera move to AE but that wasn't working. After much experimentation I found that the Transmotion POI plugin from Al Steet gave me the closest results, but the camera was unacceptably shaky. I think it's because the virtual target the plugin creates (to simulate AE's 3D camera point of interest parameter) is only around 20m in front of the camera. My camera is moving 1000's of kilometers over the course of the scene, and when the point of interest is that close there aren't enough decimal places to make smooth motion. I thought that if I moved the target much farther away that would smooth the motion. My idea was to create this target null in LW, parent it 2Mm in front of the camera, bake that motion, unparent the null from the camera, set the camera to point at that null, then run the plugin using the null to generate the point of interest data.

But, as usual, it doesn't work.

LW 8.3, Mac OS 10.3.5, 6GB RAM

Thanks.

Shawn Marshall
Marshall Arts Motion Graphics

Dodgy
01-23-2006, 05:13 PM
It looks like the baked motion is being added onto itself...

WShawn
01-23-2006, 08:06 PM
Has this actually worked for anybody in LW 8.3?

I thought the problem might be that I was working at these huge scales, but that doesn't seem to be the problem. I created a test scene in which I parented a null to the camera, positioned 2m in front of the camera, and animated the camera. I added the motion baker in the motion option panel and as soon as I started dragging the time slider the fun began. The null object spiraled outwards in all sorts of weird patterns.

I then simplified the scene. I parented the null to another null that had no keyframes. If I had the parent null at 0,0,0 HPB, then run Motion Baker on the child null, the child null would start to drift, even though its parent wasn't moving at all.

If I set the initial heading of the parent null to 27 degrees (no other keyframes), then start motion baker on the child null, the child null starts orbiting the parent null. If you add tilt to the parent null and motion bake the child null the child null spirals up.

For the love of Jeebus, I wish these things would work properly.

I've attached a test scene. Select the child null, hit "m" to open the motion options, activate the Motion Baker and drag the time slider. Does the child null start to orbit the parent null? It does for me.

Thanks

Shawn Marshall
Marshall Arts Motion Graphics

jeremyhardin
01-24-2006, 12:03 AM
yeah, motion baker sucks. just tested it and had the same problem.

a better way to bake motion (assuming you have LW8) is to parent your null as you want and open up the dope track. right click select the range you want to bake and select Baking >> Bake Keyframes.

Works like a charm.

jeremyhardin
01-24-2006, 10:20 AM
yeah, the above method doesn't work. null snaps back to it's position when it's unparented.

but... i found a workaround solution.

use motion baker.
set it to not use existing channels (so it creates new channels called AfterIK.Null.X or something like that)
play your timeline and let it bake on every frame.
open graph editor and doubleclick on your null's name in the bottom left box.
the new channels are now under the old ones. copy and paste AfterIK's X to X, etc.
do this with all your baked channels.
remove motion baker.

voila! :D

WShawn
01-24-2006, 01:54 PM
Jeremy:

YOU DA MAN!

That's a great solution, and it worked perfectly with my scene. This helps open up a whole new world of possibilities for me to integrate Lightwave renders into the After Effects 3D realm.

I looked at the Extra Channels option in the manual, but the description "Places the keys in a special AfterIK channel group—you might use these with expressions" wasn't very illuminating.

I think the strange results I was getting when I selected Use Existing was due to a sort of feedback loop, as Dodgy mentioned above. Motion Baker would create a new frame, then add that to the position of the parent object, create a new frame and add it to that new position, etc.

Thank you so much for taking the time to help troubleshoot and solve this problem. I really appreciate it.

Shawn Marshall
Marshall Arts Motion Graphics