MEL set attr. but only Z

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Old 03 March 2013   #1
MEL set attr. but only Z

Hi there,

i want to change the z rotation of a particle. But i want to keep the X,Y rotation of each particle as it is.

when i use the following expression:

particle2_grassShape.rotationPP = <<0,0,rand(0,360)>>;

i change the X,Y value to 0, which is not, what i want. But i don´t know, how i can change only the Z value.

any hints?
thank you!
Old 03 March 2013   #2
I think you can do this

vector $rot = particle2_grassShape.rotationPP;
particle2_grassShape.rotationPP = <<$rot.x,$rot.y,rand(0,360)>>;

Old 03 March 2013   #3
thank you for your help. sadly, it doesn´t work, even with a new particle system. Do i anything wrong?

Thank you!!!
Old 03 March 2013   #4
Particles need some special calls, so the best is you use the particle/nParticle command and then query or edit the attributes. You cant change the values relatively, so if you add something on top you need to query the values first:

float $r[] = `particle -attribute rotationPP -id 123 -query particleShape1`;
particle -edit -attribute "rotationPP" -id 123 -vectorValue $r[0] ($r[1] + 5) $r[2] particleShape1;

and note the position of the "-query" flag at the end before the object name
Old 03 March 2013   #5
Hey Toby, I just tested my code and it works here.

vector $rot = particle2_grassShape.rotationPP;
particle2_grassShape.rotationPP = <<$rot.x,$rot.y,rand(0,360)>>;

This expression wil randomly change only the z rotation each sub-step. I'm guessing that is probably not what you want. Are you trying to roll the particles at random speeds maybe? I'm happy to help further, but figure I'd ask what you are trying to achieve first.

@zaskar: This is an expression, not a mel script. You can do things in expressions more directly than in mel. The syntax is slightly different.

Old 03 March 2013   #6
djx, thank you, it works now!!! :-)
Old 03 March 2013   #7
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