Scaling force influence based on particle age

[draxysd]

Hi everybody,

I want to have a bit of control over my simulations (in this case flip, but it would be good to have a general dop workflow).

I want to be able to apply a force based on my particle age (or in general based on a point attribute). What would be the best way to do this? I was thinking of fiddling with popwrangle. If this is the right way, do I affect the velocity or some other attribute of the points?

Thanks in advance

 

[jamesr]

Depending on the type of force you're after, you can make a "pop force", and affect the different parameters in there using VEXpressions if you'd like! 

for instance, to apply an upward force that increases as the particles get older...

force.y = @age * 0.1;

make sure you check the correct "VEXpressions" checkbox though. There's two in there, one for the direction and another for the noise parameters.

[jamesr]

Also, that's not to say you can't do similar things with POP Wrangles. You could write one, but you'd need to affect something like force or velocity .

For instance:

@force += set(0,@age*chf("mult"),0);

Would add to the force each frame the age of the particle * some multiplier value. Keep in mind @force is read automatically in DOPs by the popsolver and integrated into the sim, but if you wanted to do a similar effect in SOPs using a solver SOP, you'd need to do something like accumulate your custom force to the velocity (@v) and finally apply to the point's position (@P) (Look into Euler Integration if you're interested in that).

Edited August 11, 2017 by jamesr

[draxysd]

Thanks for your reply James, very insightful stuff. How about affecting standard dop forces on a per point basis. One thing that comes to mind as a workaround is to make a volume from the attribute on each frame in SOP solver and use that as a mask for the DOP Force. Not as precise but if you don't have much particle interpenetration, should work. I just have to wrap my head around how to build this.

Edited August 11, 2017 by draxysd