Hi,

i'm trying to recreate the comet shown in the picture below using fluids but i am getting nowhere. Can you please assist me?

Thank you,

Paul

why fluids?

Particles, would (in my opinion) be a better solution for something like that.

Will particles be able to have that streak effect?

I come from Maya and I am not that educated with Houdini's dynamics, yet.

Well
- a ball emitting particules, then some houdini magic to make the trail… I think there is a tutorial about missile tail that could be modified to look like a comet.
Fluid looks impressive, but a lot of things can still be made with particles… all my water splash and fire are done with the lovely POP…

Fluids have their uses, but are also used in many instances when they are overkill. Unless you require fluidic motion, you are typically better off trying other methods.

In this case, you could probably get the look with a sphere emitting particles with lifespan. A bit of variance on their emission so that they go off in a cone shape. Use a color pop to control the alpha based on the lifespan, and you could probably layer this to get the different colors, or use some fancy expressions to do it in a single pass.

I do not have to use a certain technique in particular, I just need to be able to achieve that look. If particles is the way to go, I'm up for it. I have some experience in working with POPs. Are there any guide lines I should take into consideration?

Thanks

Here a simple setup in POP.
And as Allegro said use the color ramp in your shader.
I will try to get something in a couple of hours with the shader.

fluids? POPs? why bother with dynamic solvers at all? a nice analytic method is usually waaay better.

The photo looks like it could be recreated with some simple geometry and a decent custom shader. No dynamics needed….

yeah?

I'm with Ivan. Comets don't do much.

Procedurally:
1./ grid sop - poly - divs 8*1 - size 1*1 - center 0.5,0,0
2./ point sop - Use alpha. set to $TX
3./ copy sop - make 20 cumulative copies with random length scaling in X
4./ set up a ramp in COPs. make colors transition like picture
5./ use $TX to index into ramp to get point color
6./ primitive sop - rotate some random amount around z axis
7./ copy spheres to points (pscale (point sop) will effect each scale. transfer attributes (Cd, Alpha)
8./ shader with alpha para/perp (use dot product from I and N to scale opacity)

or something like that.

I would try combining two or three volumetric cone lights, with image based slide projections to shape the streaks, diffferent falloffs etc.. might just work.

note that the stuff that comes off a comet travels in a straight line - no variance at all…