Slowing And Stopping Instance Rotation

[bjohnston]

I want to slow down my instance random rotation as my particle velocity decreases. I would also like to stop the veloity below a certain value. Does anyone know the most efficient way to create an expression for this?

Thanks!

[duncanbrinsmead]

You could simply add the velocity times some factor to your per particle rotation attribute in a runtime expression(the instancer rotations would need to also be set to use your per particle rotation attribute). As the velocity goes to zero the rate of rotation change would as well.

Duncan

[chartt]

What about using a reverse linstep based on the velocity. If the particle/instance is moving along quickly, you want fast rotation. Then you want to slow the rotation with reduced velocity.

The velocity will all have to be changed to magnitude numbers:

float $slow = you enter the lowest speed of where rotation will stop (value)
float $fast = you enter the fastest speed where rotation is full on (value)
float $vel = mag(velocity);

Then you multiple your rotation by:

(1-linstep($slow, $fast, $vel)

Chris