trackball rotation

[Jonathan Lettvin]

Normally, rotation of an object is around the object's already rotated axes.

Objects tumble unintuitively (i.e. down 90, then left 90 rotates the wrong axis).

I am planning to copy the axes out of the object, rotating using different math,

and copying the rotated axes back into the object.

Has this already been done in vpython, and how do I use it?

[Bruce Sherwood]

Not sure I understand the question, but maybe this page on rotations in the documentation  may be helpful:

   https://www.glowscript.org/docs/VPythonDocs/rotation.html

Bruce

[Jonathan Lettvin]

Thank you, I have scrutinized that page much, and glad you sent the reference.  f3d offers an option to rotate objects as if mounted on your trackball.  Vpython does not.  If useful, I will write a MWE.py to illustrate. 

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[Jonathan Lettvin]

f3d offers an option to rotate objects as if mounted on your trackball.  Vpython does not.

Download f3d and use the following command line to see f3d at work:

Specifically, try rotation before and after toggling trackball mode using the 'k' key.

One mode tumbles unintuitively, the other mode feels natural.

I want Vpython to support the natural feeling one.

f3d paraboloid.obj \
--camera-position=0,10,0 \
--camera-focal-point=0,0,0 \
--camera-view-angle=45 \
--point-sprites-size=40 \
--point-sprites=true \
--background-color=0.5,0.5,0.5 \
-k

Contents of the file paraboloid.obj

# paraboloid.obj

o paraboloid

v +0 +0 +0 255 255 255

v +1 +0 +1 1 0 0
v +0 +1 +1 1 0 0
v -1 +0 +1 1 0 0
v +0 -1 +1 1 0 0

v +1 +1 +2 0 1 0
v +1 -1 +2 0 1 0
v -1 +1 +2 0 1 0
v -1 -1 +2 0 1 0