Retargeting research

I wanted to experiment with retargetting motion with constraints from one joint chain to another but as I don't have the motion capture data I'd need yet I've set up some simple tests in Maya.

Firstly I've decided to just try applying movement from one joint to another without any complex rigs in place but then I think it would be a good idea to try and apply the movement to the lamp rig just to check the rig doesn't interfere or vice versa.

I've set up three tests: Uniform movement translation, non-uniform movement and then this multiply node that reverses movement to just double check it does what Norbert says it does (which i don't doubt) but also to check i know how to use it.

First test I've used a parent constraint which seems to work fine so long as you  have the joint chain in the same position as the source but if not then limit the constraints to just the rotation planes, having translation causes the entire joint chain to move and gives undesirable results. And if the joint chain doesn't match the orientation of the joint then again undesirable results are seen in the path of the movement...

I've been reading a paper by Hsieh, Chen and Ouhyoung from Taiwan University:

http://graphics.im.ntu.edu.tw/docs/cadcg05_hsieh.pdf

 Which actually looks at retargetting to different articulated figures and it looks like the best solution they came up with it to make a transition skeleton. This takes away the issues that were had with trying to retarget to a bone with a different orientation. They combat the difference in quantities of bones that make up the skeleton by applying the same motion from one source bone to many target bones. 

They create the skeleton by re positioning each target bone of the transition skeleton to align with each source bone.

While they do align the bones core direction they do not consider the twist in the bones which can lead to some unexpected results.

Mocap Session

I recently had another session in the MoCap suit this time with Charlie in the suit, hoping to be able to get it up and running using a human template I hit some varied success but the new setup of markers was a little problematic and will need remedying. for example the right leg being tied so closely to the left causes a lot of occlusion which made the time for cleanup lengthy however it seemed that this could be fixed with only one set of markers on the leg being used.

As you can see from this screenshot the template itself did take to the markers and was responding in a reasonable manner.

Even if there were a couple of glitches like his right leg becoming detached...

Overall the main problem that kept recurring was how best to limit the movement. The clingfilm was bound around the upper legs and then again separately around the lower legs to allow for movement around the knees but this still seemed to limit the movement a little too much leaving much of the actions stiff which could affect performance. The clingfilm also slipped out of place moving the markers that were on top of it but this was solved using some double sided sticky tape to secure it in place. The feet wouldn't stay together either but binding them together would have made Charlie a little too unstable as he was already a bit shaky. We did place crash mats around in order to protect him a little and Mike was close by to give physical support if he needed it.

If I go with only using the one leg of markers then I wouldn't need to cling film him at all but it may make the balance look a little off... sacrifices sacrifices...

At this rate it seems much less hassle to just keyframe animate the lamp however it may be more worthwhile for more complex characters.. but maybe not.