Rotate from (0,1,0) to (0,-1,0) with dihedral

[Alexey Vanzhula]

There is dihedral vex and hscriptExpression functions to calculate rotations.

How to rotate for example from (0,-1,0) to (0,1,0), when angle between vectors is 180°.

I can parse vangle hscriptExpression function result with if statement, but what is correct decision ?

Edited July 31, 2014 by Alexey Vanzhula

[anim]

dihedral will compute rotation from {0,-1,0} to {0,1,0} with no problems

the only catch is that there is infinite number of possible rotations between opposite vectors as there is no rotation axis strictly defined as in the case when those vectors are not parallel

so you need to define perpendicular axis to these vectors to rotate about if you really care about exact rotation

 

so once you have your perpendicular axis you can just use

rotaxis() expression function

or

quaternion(angleaxis) or quaternion(angle, axis) or rotate() VEX functions

 

to get your desired rotation

[Alexey Vanzhula]

Thank you very much!