FBXSDK, using Quaternions to set rotation keys? - c++

Question

I am trying to write a file save application using the Autodesk FBXSDK. I have this working fine using Euler rotations, but I need to update it to use quaternions.
The relevant function is:
bool CreateScene(FbxScene* pScene, double lFocalLength, int startFrame)
{
//Create Camera
FbxNode* lMyCameraNode = FbxNode::Create(pScene, "p_camera");
//connect camera node to root node
FbxNode* lRootNode = pScene->GetRootNode();
lRootNode->ConnectSrcObject(lMyCameraNode);
FbxCamera* lMyCamera = FbxCamera::Create(pScene, "Root_camera");
lMyCameraNode->SetNodeAttribute(lMyCamera);
// Create an animation stack
FbxAnimStack* myAnimStack = FbxAnimStack::Create(pScene, "My stack");
// Create the base layer (this is mandatory)
FbxAnimLayer* pAnimLayer = FbxAnimLayer::Create(pScene, "Layer0");
myAnimStack->AddMember(pAnimLayer);
// Get the camera’s curve node for local translation.
FbxAnimCurveNode* myAnimCurveNodeRot = lMyCameraNode->LclRotation.GetCurveNode(pAnimLayer, true);
//create curve nodes
FbxAnimCurve* myRotXCurve = NULL;
FbxAnimCurve* myRotYCurve = NULL;
FbxAnimCurve* myRotZCurve = NULL;
FbxTime lTime; // For the start and stop keys. int lKeyIndex = 0; // Index for the keys that define the curve
// Get the animation curve for local rotation of the camera.
myRotXCurve = lMyCameraNode->LclRotation.GetCurve(pAnimLayer, FBXSDK_CURVENODE_COMPONENT_X, true);
myRotYCurve = lMyCameraNode->LclRotation.GetCurve(pAnimLayer, FBXSDK_CURVENODE_COMPONENT_Y, true);
myRotZCurve = lMyCameraNode->LclRotation.GetCurve(pAnimLayer, FBXSDK_CURVENODE_COMPONENT_Z, true);
//This to add keys, per frame.
float frameNumber = startFrame;
for (int i = 0; i < rec.size(); i++)
{
lTime.SetFrame(frameNumber); //frame number
//rx
lKeyIndex = myRotXCurve->KeyAdd(lTime);
myRotXCurve->KeySet(lKeyIndex, lTime, recRotX[i], FbxAnimCurveDef::eInterpolationLinear);
//ry
lKeyIndex = myRotYCurve->KeyAdd(lTime);
myRotYCurve->KeySet(lKeyIndex, lTime, recRotY[i], FbxAnimCurveDef::eInterpolationLinear);
//rz
lKeyIndex = myRotZCurve->KeyAdd(lTime);
myRotZCurve->KeySet(lKeyIndex, lTime, recRotZ[i], FbxAnimCurveDef::eInterpolationLinear);
frameNumber += 1;
}
return true;
}
I would ideally like to pass in quaternion data here, instead of the euler x,y,z values. Is this possible with the fbxsdk? or do I need to convert my quaternion data first, and continue to pass in eulers?
Thank you.

Answer 1

You always need to go back to Euler angles, as you can only get animation curves for the XYZ rotation. The only thing you have control over is the rotation order.
However, you can use FbxQuaternion for your calculations, then use .DecomposeSphericalXYZ() to get XYZ Euler angles.

Answer 2

The accepted answer does not work. Although the documentation definitely implies it should,
Create an Euler XYZ equivalent to the current quaternion.
An Autodesk employee claims that it does not
DecomposeSphericalXYZ does not convert to Euler angles
and this is borne out by my testing. In the current FBX SDK, there are at least two relatively easy ways you can convert a quat to what they call an euler, or to something suitable for LclRotation. First is via FbxAMatrix
FbxQuaternion fq = ...;
FbxAMatrix fa;
fa.SetQ(fq);
FbxVector4 fe = fa.GetR();
Second is via FbxVector::SetXYZ
FbxVector4 fe2;
fe2.SetXYZ(fq);
I've successfully gone from an XYZ rotation sequence → quaternion → euler from both methods, and retrieved the same rotation sequence. When I use DecomposeSphericalXYZ I get a slightly different FbxVector4. I haven't tried to figure out what they mean by "euler in spherical coordinates".

Answer 3

Years later, I hit this issue again, and found a simple answer.
After you have set all the keys that you need, just use this filter:
FbxAnimCurveFilterUnroll filter;
filter.Apply(*myAnimCurveNodeRot);
This seems to function the same as the 'Euler Filter' in Maya, or the 'Gimbal Killer' filter in Motionbuilder.