How does ZED CHOP convert from quaternions to Euler angles?

YumaTaesu_td · February 7, 2024, 7:34am

I’m attempting to create a simple motion capture viewer using ZED CHOP. I’m testing with UE5’s Manny imported into TouchDesigner, but I’m having trouble with the rotations.

ZED CHOP has a “Relative, with Orientation” mode in JointMode, which returns Euler angles.

It seems like ZED CHOP internally converts quaternions to Euler angles, but how does it perform this conversion?

Originally, the ZED SDK seems to return quaternions as “Local orientation per joint.” In ZED’s UE Animation Blueprint, it simply applies this local orientation per joint. The motion capture example for zed-UE5 works perfectly with same Manny.

github.com

stereolabs/zed-UE5/blob/main/Plugins/Stereolabs/Source/ZED/Private/Core/AnimNode_ZEDPose.cpp#L301-L320


      
              Rotation = FQuat::Slerp(
                  PreviousRotations[idx],
                  BodyData.LocalOrientationPerJoint[idx],
                  FMath::Clamp(RotationSlerpIntensity, 0.0f, 1.0f)
              );
              PreviousRotations[idx] = Rotation;
          
              Translation = OutPose[CPIndex].GetTranslation();
              if (Translation.ContainsNaN())
              {
                  Translation = FVector::ZeroVector;
              }
          }
          
          if (bMirrorOnZAxis) {
              Rotation.W *= -1.f;
              Rotation.Y *= -1.f;
          }
          
          FQuat FinalRotation = Rotation * OutPose[CPIndex].GetRotation();

malcolm · February 8, 2024, 9:09pm

How is your object COMP hierarchy setup? We leave the values as relative, so you need to have your hierarchy setup with relative transforms via wires as well.
We extract the rotates into eulers directly and output those, they are not combined with any other transform before we output them.

YumaTaesu_td · February 9, 2024, 1:02am

Thank you for your help !
I’ll check it later.