# FLIP Energy transfer?

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Is there a way to calculate or obtain the degree of energy imposed onto FLIP particles resulting from collision as either a scalar or vector value?

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If you subtract the velocity of the previous frame from the current frame, that would give you the direction and magnitude of the "force" that affected your sim that frame.

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Ok. That was kind of my plan. I suppose I could use a POP Collision(?) DOP to isolate RBD- collided flip particles ... haven't used that node for a while....

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That would probably work, although I have found the POP collision node to be unreliable with FLIP if your particle count is changing rapidly (like if you have reseed on). You may consider using a sop solver with the "xyz distance" node to make your own collision detection.

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you can do this after simulation also

drop a wrangle, connect the same cache with a 1 frame offset to second input

vector oldspeed = point(1,"v",@id);    \\get the previous frame point velocity vector

float speed1 = length2(@v); \\ measure current speed

float speed2 = length2(oldspeed); \\ measure previous speed

f@ratio = abs(speed1/speed2); \\ get the change ratio

basically, if the ratio is 1 then speed hasn`t changed and vice versa, or sth like that

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Another issue is that this would account for all force, not just collisions... Though this might not be a problem.

And yeah, i would do it in a SOP solver. I want to take a stab at non-Newtonian fluids that change viscosity with force.

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Ahh... For non-Newtonian you may want to look at pressure. You can turn the pressure field into a particle attribute by using the "gas field to particle" gas microsolver. Then use that to drive the viscosity or something.

See attached for a quick example.

pressure.hip

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2 hours ago, KarlRichter said:

Ahh... For non-Newtonian you may want to look at pressure. You can turn the pressure field into a particle attribute by using the "gas field to particle" gas microsolver. Then use that to drive the viscosity or something.

See attached for a quick example.

wait. the what to WHAT?

Oh this is going to get fun. I knew that there was something like this, just wasn't sure how to get to it! THANKS.

Edited by shawn_kearney

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