IsRotate property of Transform reports incorrectly

[csykes]

I’m debugging a plugin and trying to confirm if a transformation is a rotation. I am taking the rotation from DynamicTransform as a result of manipulating the gumball. If I use the rotation parts of the gumball the Transform object doesn’t report IsRotation correctly.

I’ve created a simple Project Example here.
IsRotationExample.zip (141.2 KB)
IsRotationExample.rhp (40.5 KB)

[rajaa (Rajaa Issa)]

I do see that even when running the Rhino Rotate command, the first few mouse locations are confirming a rotation, but then switch to not-rotation. The IsLinear test seems to be failing also.
@mikko can you help clarify this behavior?

[dale (Dale Fugier)]

This seems to work:

var xform = Transform.Rotation(0.401426, Point3d.Origin);
RhinoApp.WriteLine("Transform.IsRotation = {0}", xform.IsRotation);

– Dale

[csykes]

Does this mean IsLinear and IsRotation will only return true if the Transformation was explicitly called as a Rotation or a Translation. And doesn’t actually analyse the Transform to see if it counts as a Translation or Rotation?

[dale (Dale Fugier)]

@csykes

Does this mean IsLinear and IsRotation will only return true if the Transformation was explicitly called as a Rotation or a Translation.

No

@csykes

And doesn’t actually analyse the Transform to see if it counts as a Translation or Rotation?

Yes

mcneel/opennurbs/blob/2b96cf31429dab25bf8a1dbd171227c506b06f88/opennurbs_xform.cpp#L1493

– Dale