Howdy -
I thought this would be easy to do in CHOPS but it turned out to be a bit more challenging than expected.

The objects in my scene are animated to a static camera. I want to be able to take the transformations in one object, solve for the inverse and apply them back on to the camera such that the camera is animated, not the object.

In CHOPS I was able create an inverse matrix in a VOPS network. I solved for the translations no problem. The rotations are turning into a beast. Not only is constructing the rotational matrix ugly, but extracting the euler angles from the inverse matrix is monstrous (It involves ATans and what not).

Before I get too deep into this, can anyone suggest a better strategy for solving this problem?

Thanks!

This might be of use. It doesn't use CHOPs, but it takes whatever input object you give it and using a simple Python call outputs the inverse of that objects transform.

http://houdinitoolbox.com/houdini.php?asset=51 [houdinitoolbox.com]

hi, someone asked how to do the inverse thing on odfoce, here's the thread

http://forums.odforce.net/index.php?/topic/12964-inverting-camerascene-transformations/ [forums.odforce.net]


here's using that same technique to do what you're trying to do - using inverted object xformations to animate the camera. i imagine this is really similar to what you're already doing, but getting the rotations out of the inverted xform is pretty easy - just using the extract xform vop.

the nice thing about doing this type of thing this way with chops + vex is that you can use the transform chop to filter out any euiler angle flipping. other techniques make it tough to check for temporal coherence.

Thanks Guys!

These solutions totally rock and pretty much do exactly what I need to do.

I haven't been able to play around with the solutions much but it looks like I have a great head start!

Cheers!

Doesn't the Object CHOP work?