Particle rotation driven by chops

[Lukich]

Hi. I am trying to control the particle rotation using chops, by exporting the rotx, roty, rotz, and rotangle to chops and adding to them a Ramp wave. It works, but for some reason instead of a uniform motion that I'd expect from a Ramp, I get a faster movement at the beginning, which drastically slows down towards the end. I have no idea why it'd behave like that, maybe you guys can point me in the right direction?

I'm attaching an example file.

Thanks,

Luka

chopRotation.hip.zip

[stabby]

The 'rot' attribute is a quaternion, and the 4 numbers don't correspond directly to $rotx, $roty, $rotz and $rota. The actual equations are:

rot[0] = rotx * sin(rota/2)

rot[1] = roty * sin(rota/2)

rot[2] = rotz * sin(rota/2)

rot[3] = cos(rota/2)

(this is assuming your axis is already normalized)

Hi. I am trying to control the particle rotation using chops, by exporting the rotx, roty, rotz, and rotangle to chops and adding to them a Ramp wave. It works, but for some reason instead of a uniform motion that I'd expect from a Ramp, I get a faster movement at the beginning, which drastically slows down towards the end. I have no idea why it'd behave like that, maybe you guys can point me in the right direction?

I'm attaching an example file.

Thanks,

Luka

[Lukich]

I eventually figured out how to do it with chops, but thanks a lot for your response, it's good to know this math, will come in handy. Thanks!