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# Particle physics

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### #1IForgot  Members

Posted 10 December 2012 - 11:15 AM

Hi all!

This is my first post on this forum so sorry if this is in the wrong place :/

I am starting a hobby project before I graduate and have to start actually acting like an adult. I want to make a "wisp" effect. I am familiar with particles and I know what I want to do with lighting, cel shading and whatnot but my main problem is that I am not sure how to attack making a "trail".
Now I am sorry if I fail at describing this, but if you think about letting an imaginary particle outside move on a path it would have tails (on its trail) not just going right in back of it but also branching out left and right and swirling around. I am by no means a super great math/physics guy so I am kind of stuck on how to make the particles behave like this. If I do random wind values I am afraid that it might look sort of sporadic and less flowing.

Well once again, sorry if this is in the wrong board or if I missed a previous topic on it. Thanks in advance everyone!

### #2deftware  Prime Members

Posted 12 December 2012 - 02:18 AM

you want fluid dynamics.. basically, you set up a grid of velocities. the object emitting particles affects the velocities of these grid squares/cubes as it moves through them (depending on whether you're creating a 2D or 3D simulation) which in-turn affect eachother, not forgetting to incorporate a friction function that dampens the velocities over time..

the trick is knowing how the velocities should affect eachother. they shouldn't necessarily average-together as the actual physics are a bit more complicated. i'm no expert on fluid dynamics, but I know that this is the general approach - defining the motion of individual units of space. how the grid-squares affect eachother over time is what you want to read up on.

at the end of the day what you are doing is creating particles that are affected by the 'velocity' of the grid squares/cubes they are in.. the coarser your velocity grid resolution, the faster your simulation will run, but the less realistic-looking the simulation will be..

i'm sure there are other tricks to optimize such a setup, perhaps the use of a quad/oct tree, so that only areas of high-variance in velocities are considered as many small nodes, and large stationary areas consist of a few large nodes.

good luck.

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