topic Re: Interpolating Quaternions in MotionBuilder Forum

Interpolating Quaternions

Anonymous — Tue, 26 May 2015 16:31:02 GMT

Hello,

I am using the FBX SDK to export data from a motion sensor in FBX format, and I am currently loading it in MotionBuilder.

My original data is provided in quaternions, and then I create keyframes based on my joint information. The problem is that it does not seem to be possible to create these keyframes from quaternions. First, I have to convert them to euler angles before that. Please correct me if I am wrong.

The problem is that I am getting these Gimbal lock effects when I do that. The animation looks fine after using Motionbuilder's GimbalKiller filter, but for my application I might not be able to use these kind of post-processing filters. It also does not seem like an optimal solution. I don't even want to convert to Euler in the first place, but I did not find a way around this.

I noticed the SDK has a constant to set the rotation type :"FbxLimitsUtilities::ERotationType::eQuaternion", but I am not sure how to use it.

Whenever I create a new key, it seems to expect Euler angles, no matter what.

Is it possible to use quaternions at all?

Re: Interpolating Quaternions

Anonymous — Wed, 27 May 2015 16:08:20 GMT

Hi Marco,

Maybe you can try FBGetContinuousRotation() after converting your rotation in euler.

http://docs.autodesk.com/MB/2014/ENU/MotionBuilder-SDK-Documentation/index.html?url=py_ref/group__pyfbsdk.html,topicNumber=py_ref_group__pyfbsdk_htmlb6a2c985-343d-49a1-bb10-0b41e9cee488,hash=gace04bc6ca4ab90cc95c9d9214522a5ff

http://docs.autodesk.com/MB/2014/ENU/MotionBuilder-SDK-Documentation/py_ref/_samples_2_math_2_math_utilities_8py-example.html

Good luck

Re: Interpolating Quaternions

Anonymous — Thu, 28 May 2015 04:41:13 GMT

Thanks bujinkan

I was thinking about the FBX C++ SDK, I did not find the equivalent of FBGetContinuousRotation() there.

I decided to use, at least for now, the class FbxAnimCurveFilterUnroll, which does the job. I run it as a post-processing step, after all keys have been exported.