Could someone indicate the exact operations FEMAP does when transforming 3 rotations to a dircos matrix? I can't replicate exactly the calculation...
Do you mean an API for converting a sequence of rotations about the fixed axes X, then Y then Z into direction cosines with respect to the same axes?
The attached link may be useful, if perhaps much more than you need...
Thanks but not quite. I'm aware of the maths, and the API methods already exist in FEMAP, cf app.feRotationToDirCos. What I want is to use these methods to accelerate a process, but I need to check exactly what the API method does. And so far I can't replicate exactly what it does.
Reading the helpl I thought FEMAP started with rotX, then around the rotated Y, then around the doubly rotated Z. But in that case I would expect the term [3,1] to be sin(2nd rotation) and that's not what is returned by the method...
If a developper has an eye on the code and can indicate what calculation is done I would appreciate it;
Nevermind I found my mistake: FEMAP thinks in degrees not radians.
So the 1rst order of calculation for the RotationToDirCos method is simply
[1, sin(Rz),-sin(Ry) ; -sin(Rz), 1, sin(Rx) ; sin(Ry), -sin(Rx), 1]