# another particle velocity question

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hello! another problem:

if i use:

location pop --> wind pop - everything is OK.

if i use:

location pop --> velocity (or position) pop --> wind pop,

wind node is 'ignored', there is no effect of the force, as 'velocity' node is much stronger)

how can i apply forces to the particles, which move using 'manually' entered position or velocity?

Edited by mic
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hello! another problem:

if i use:

location pop --> wind pop - everything is OK.

if i use:

location pop --> velocity (or position) pop --> wind pop,

wind node is 'ignored', there is no effect of the force, as 'velocity' node is much stronger)

how can i apply forces to the particles, which move using 'manually' entered position or velocity?

I kind of not understands your question properly, but if you just wanted to control the movement of the way particles are moving, then right after your wind node, apply speedlimit node to control the min and max value of particles.

Is this what you are looking for..?

Cheers,

Junaid

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I kind of not understands your question properly, but if you just wanted to control the movement of the way particles are moving, then right after your wind node, apply speedlimit node to control the min and max value of particles.

Is this what you are looking for..?

Cheers,

Junaid

thank you, Junaid, but that's not i want.. My question is very simple: if i have velocity node, for example v = (1, 1, 0) - that means that NO force will change these values! if i apply any force after velocity POP, for example, wind POP with some direction - it won't change the behavior of particles! the velocity and position POP locks the further changing the position of particles!

and in my network, the motion was set using velocity POP. now i eant to add some turbulence and as i see i can't do it.

the only solution i have - to change velocity POP to wind POP with the same expressions. That's not very bad)

if you don't still get a point of what i mean i can post the scene.. maybe i'm somewhere awfully wrong..

(funny - at last topic i changed type from position to velocity for motion-blur render, and now i am changing velocity to wind for applying turbulence))

Edited by mic
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thank you, Junaid, but that's not i want.. My question is very simple: if i have velocity node, for example v = (1, 1, 0) - that means that NO force will change these values! if i apply any force after velocity POP, for example, wind POP with some direction - it won't change the behavior of particles! the velocity and position POP locks the further changing the position of particles!

and in my network, the motion was set using velocity POP. now i eant to add some turbulence and as i see i can't do it.

the only solution i have - to change velocity POP to wind POP with the same expressions. That's not very bad)

if you don't still get a point of what i mean i can post the scene.. maybe i'm somewhere awfully wrong..

(funny - at last topic i changed type from position to velocity for motion-blur render, and now i am changing velocity to wind for applying turbulence))

The Velocity and Position POP override any existing velocity or position attributes. POPs is a simulation, so it takes into account every node first, then performs the simulation. Generally, the order in which the POPs are in does not matter (unless its a split/soucre/collect POP...etc). One way to solve your problem would be keep \$VX, \$VY, \$VZ in your Velocity POP and add whatever your are currently using so it would be something like this \$VX + 1, \$VY + 1, \$VZ + 0. This allows it to take into account any additional or existing velocity.

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aha, thank you, Spencer, that's idea!)

can't check it right now (rendering=)) but as you said i can use wind POP first (turbulence) and AFTER it drop velocity POP with my super-artful-expressions added to \$VX, \$VY, \$VZ!))

Edited by mic
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aha, thank you, Spencer, that's idea!)

can't check it right now (rendering=)) but as you said i can use wind POP first (turbulence) and AFTER it drop velocity POP with my super-artful-expressions added to \$VX, \$VY, \$VZ!))

No problem, but I just want to reiterate that it does NOT matter the order your POPs are placed in your network, unless its a split, source, collect, etc... since it evaluates them all before actually moving the particle so you could have your Velocity POP before or after the Wind POP. It will have the same result. Visually, for you, it may make more sense to have it in one order vs another but in the end Houdini does not care either way.

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thanks, Spencer, that's important for understanding, indeed.

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hi Spencer, sorry for the delay - only now i could try your suggestions, and maybe we are somewhere mistaken..

please look at the scene attached..

as you see, velocity POP overrides all, as you said..

upd.

SORRY-SORRY, everything is ok! the reason was the velocity values are very large - and turbulence is very small, so the result wasn't seen) and detail view shows everything)

so, the problem solved, thanks to all, especially to Spencer)

particle_velocity_test_v01.hip

Edited by mic

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