Isotropix Forums

Hi,

I'm trying to get the quaternion of an object from its global matrix.
When I run this code:

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rotMatrix = ix.api.GMathMatrix4x4d()
matrix.extract_rotation(rotMatrix)
rotQuat = ix.api.GMathQuat()
rotQuat.set_rotation(rotMatrix)

I'm getting the following error:

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TypeError: Wrong number or type of arguments for overloaded function 'GMathQuat_set_rotation'.
  Possible C/C++ prototypes are:
    GMathQuaternion< double >::set_rotation(double const &,GMathVec3d const &)
    GMathQuaternion< double >::set_rotation(GMathVec3d const &,GMathVec3d const &

While in the documentation it says that we should be able to do it from a rotation matrix if I'm not wrong:

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set_rotation (const U &m)
U   The type of the input matrix. It's automatically deduced, and works with 3x3 and 4x4 matrices.

I also tried to set the rotation for each angle and rotation axis, but then I'm not quite sure how I could combine them to get the global quaternion of the object:

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rotate = ix.api.GMathVec3d()
matrix.compute_euler_angles(rotate)

xRot = rotate[0]
yRot = rotate[1]
zRot = rotate[2]

xRotAxis = ix.api.GMathVec3d(1,0,0)
yRotAxis = ix.api.GMathVec3d(0,1,0)
zRotAxis = ix.api.GMathVec3d(0,0,1)

rotQuat = ix.api.GMathQuat()
rotQuat.set_rotation(xRot, xRotAxis)
roQquat.set_rotation(yRot, yRotAxis)
roQuat.set_rotation(zRot, zRotAxis)

So i was curious to check on this to see if you would know how to do it.

Thanks,
Jeremy

Hi Jeremy,

There are missing API bindings in Python in 5.0 SP10b, so the C++ SDK documentation is not reliable for GMathQuaternion in Python here.
It seems to be a regression from previous SPs. Sorry about that.
What version are you using?

In the meantime, here is a workaround.

python code

rotMat = ix.api.GMathMatrix4x4d() # for the sake of the example

# Extract Euler angles, default rotation order: ZXY
eulerAngles = ix.api.GMathVec3d()
rotMat.compute_euler_angles(eulerAngles)

# Rotation axes
xRotAxis = ix.api.GMathVec3d(1,0,0)
yRotAxis = ix.api.GMathVec3d(0,1,0)
zRotAxis = ix.api.GMathVec3d(0,0,1)

# Individual rotation quaternions per axis
xQuat = ix.api.GMathQuatd()
xQuat.set_rotation(eulerAngles[0], xRotAxis)
yQuat = ix.api.GMathQuatd()
yQuat.set_rotation(eulerAngles[1], yRotAxis)
zQuat = ix.api.GMathQuatd()
zQuat.set_rotation(eulerAngles[2], zRotAxis)

# Compute the final quaternion by *multiplying* in the same rotation order
rotQuat = zQuat * xQuat * yQuat

We'll fix the bindings.

Thank you for getting back on this Anthony. When I looked into the definition of the set_rotation() method, it seems to only support 3x3 matrices, so I actually tried to create a 3x3 rotation matrix from the 4x4 extracted one as I thought that it would be worth giving it a try but didn't work either after all.

Thanks for the info about the missing bindings in the Python API and for the workaround solution which I ended using, good to know that we can do it this way too as it does work fine.

I'm using Clarisse 5 SP10 by the way.

Thanks,
Jeremy

By the way, the APIs that you tried to use in your original post are now available in 5.0 SP11.
Cheers!

Thanks for the heads up regarding this Anthony. I will definitely give it a try when we update it and let you know how it goes.

Thanks,
Jeremy