Python transform.GetYawPitchRoll() returns weirdness (Trying to get transform data-> CSV)

Context (in case there’s an obvious easier way to achieve what I want):
I’m ultimately trying to get transform numbers from a list of geometries and export it as CSV: 3 translation numbers (x,y,z), 3 rotation numbers (yaw, pitch, roll) and 3 scale numbers (x, y, z).

E.g. I need a string like this for each piece of geometry:

1, 2, 1, 45, 0, 0, 40, 20, 35

representing Translate(1,2,1), Rotate(45, 0, 0), and Scale(40,20,35)

Current tactic:
I’m sending transforms into a GHPython node and parsing them into the string I want.

Current problem:
For rotations, I’m using the transform.GetYawPitchRoll() method, which returns a bool of whether the input transform represents a rotation along with the 3 angles. When it works, it should look like this:
(True, 1.5707963267948966, 0.0, 0.0)

But for certain uses of the Rotate3D node around e.g. the shape’s centroid, something is breaking and returning:
(False, -1.2343210123432101e+308, -1.2343210123432101e+308, -1.2343210123432101e+308)
(These look to me like the largest negative 64bit double values the system can create… aka ~Infinity)

The only case I’ve found where Rotate3D provides a transform that python interprets as rotation is when the center is the origin (0,0,0).

Anyone have any idea why this would be happening? Is there a better way to do what I want?

Update: Just realized I could be looking at the transform matrices, and it appears that the afflicted rotations have values in the 4th column, where translation data is stored. I don’t recognize the numbers there. Any clues what this is for? (30.1 KB)

This is what Rhino uses internally for “unset-value”, it is a special constant (and not negative infinity).

As for your transformations, you could be experiencing gimbal lock, i.e. where yaw/pitch/roll cannot be determined.

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My solution was to DecomposeAffine the rotation transform (which was unexpectedly complicated) to get the pure rotation matrix without the extra values in the 4th column, and only THEN GetYawPitchRoll() (24.4 KB)

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I’ve only applied one rotation (I mean, around one axis) so I don’t think gimbal lock applies here.

But good to know about that unset-value constant! Thanks

Did you try:

print rot1.ToFloatArray(False)