How do I match "Rotate Axis" with object rotation?

[naughty]

This is a maths question I guess, as I don't understand how cumulative angles(?) or rotation matrices(?) or whatever(!) works..?

I want to rotate an objects rotation pivot so that it matches the rotation of a second object.. And I have no idea how to do it. I can do it roughly by eye but that's no good, and I can't make sense of the angles or results I get returned when I do do it this way.

say I have a locator with a rotation of: -45 30 -4 and I want pCube1's rotation axis (pCube1.rotateAxis) aligned to exactly the same angles/direction... ..eeugh..how?

Am I being really thick here? or is this really complicated?

:nathaN

[joojaa]

it is realy complicated!

[naughty]

HahAHahahah! thanks, I was kind of hoping that was the case!.. but now I'm stuck with how to actually do what I want to do..

is the problem simply retrieving individual X, Y and Z rotations from a clumped XYZ rotation? that is the complicated bit isn't it..?

[joojaa]

no seriously make a locator and orient contrain it and read the values form there, saves you some work.

But yeah working with angles is a bit tricky.

[naughty]

hmm.. that approach doesn't seem to work.. I don't want the locator to drive the object's rotation, which is what it seems to do when I orient Constraint it.. I want the locator to drive the objects PIVOT rotation, so the object doesn't appear to move or rotate when I rotate the locator..

is this possible?

I tried:

orientConstraint locator1 pCube1.rotateAxis;

and this just rotates the cube to match the locator, and then I tried:

connectAttr locator1.r pCube1.rotateAxis;

but this does exactly the same as the above (even though different attributes get connected)

any ideas?

:nathaN

[joojaa]

i was under the impression you wnated to get rotation form one space to another.

Okay anyway, group the object rotate the group and counterrotate the object. (or if you want permanent cahge rotat freeze couter rotate) Or the other way around depending on wich you want to use local or parent space.

But truth to be told maya cant rotate the pivot in any other way realy well.

[failure]

Of you only need to rotate local rotation axis you can:

float $rot[] = getAttr locator1.rotate;
$rot[0] = -$rot[0];
$rot[1] = -$rot[1];
$rot[2] = -$rot[2];
xform -ra $rot[0] $rot[1] $rot[2] pCube1;

[naughty]

cool! I've just tried that and I think it's exactly what I'm lookng for! thanks failure.

is there a way I can connect these values together like you can with connectAttr..? so that when I rotate the locator, the pCube's rotateAxis is also dynamically updated? I've not done much with attr connecting and nothing with expressions, but I'm guessing the latter is maybe the way to achieve this (if it is even possible)

:nathaN

[failure]

You must do this with expression