STL rotation

[sree314]

Implement a rotate() method in STLConversionInfo that takes in a CADquery object and rotates it according to the rotation information stored in the STLConversionInfo object.

Also write a test for this. You can use the models in models.py to obtain test cadquery objects.

[redrn]

Did some digging in the rotation issue, looks like Shape.rotate and Shape.translate methods all returns a copy of the object where the rotation/translation is already applied. So, the getting the Location() of rotated parts results in (0, 0, 0) rotation value eventhough the part is correctly rotated as per visually checking the exported stl.

There are two ways to go about this:

1. leaving this at it be since we know the rotation is correct. We just get any meaningful rotation info in code.

2. We can use the Shape.locate(Location) method to set a translation/rotation modifier. This correctly rotates the part in place. Only issue is the each call to locate(Location) overrides the current location with the provided parameter, and constructor for Location only takes rotation for one axis in euler angle, or rotation for all three axis in quaternion. So, If we want correct rotation and access to rotation info in code, we have to create a quaternion based on our euler angles and pass it to Location constructor and call locate(Location), which shouldn't be too hard to do. I'm not sure if I should introduce an extra dependency and use Scipy.quaternion or use OCP.gp_quaternion module whose usage seems more tricky.

I'm currently exploring the second option, but I'm not sure if it is worth the effort.

[sree314]

All the API functions return "copies" of the original object. In-place rotation is neither required nor desired for STL export, so don't do 2.

I believe it should be possible to retrieve "world" rotation if you do 1. But other strategies are possible. For now, as long as the exported STL files are being rotated, we can tackle the test later when we get more familiar with the API.