Dumb one - collision objects trapping fluid voxels - best method / settings?

[joconnell]

Heya Folks!

Apologies for some dumb simple questions, I'm only really on day 2 of phoenix so there's probably some silly stuff here. I've got a setup where I'm making a small blood emitter object, I've tried keeping it within another object so it can't leak out the wrong way, then I'm animating a collision object through both to push the fluid out. I'm animating the discharge of the fluid on one frame only so it's acting like a "fill" command the frame before my impact happens. Everything is set up similar to real world size so the physics behave.

I'm getting issues where the fluid voxels are getting trapped inside the collision object which I've cleared by using the clear inside command in my collision object properties, this however ends up killing off a lot of my fluid too. I'm using inscribed mode for the collider which is a sealed, solid object. I've tried upping my voxel count in the grid so that the spacing is fine enough for the gaps between emitter and colliders to work fine, I've also tried upping the steps per frame to 8 to get more subframe accuracy. The advection method seems to make the results different but none are error free.

I could be trying to go about this the entirely wrong way, what would you guys do if you wanted to have small blood impacts react to scene objects and have some interesting splats? I've attached a really simple max 2014 file if you've got time to look at it, hopefully there's a dumb basic in there I'm missing that's causing the fluid to trap.

Phoenix_splat_001_max_2014.zip

Cheers!

John

[Ivaylo Katev]

well, this is a very common issue in the grid based core, do you have nightly access?

[joconnell]

Not for phoenix no, there seems to be some great stuff going on there so I'll definitely jump in. Reading strob's thread on a liquid emitting character I might be better off using some simple polygons and animating them forward to "throw" fluid rather than push it. Which other core is in the nightlies? Would it be more suitable for small level details like stringy splats of blood?

Cheers!

[Ivaylo Katev]

better ask the support for nightly build access, the problem you have just is not happening when you use the particle based solver. the reason for the trapped liquid is the voxelization of the geometry, the gird based simulation sees the objects like made of boxes, and the liquid is always trapped in the steps of the inclined surfaces. the particle based core does not produce this problem, because the particles are sliding on the geometry, there are no voxels and steps.

[joconnell]

On the nightlies now, is the particle core the new default when you make a liquid sim object? Is the beta forum the best place to ask questions about the nightlies? The nightlies docs don't seem to be totally up to speed with all the leaps in development you've made!

[Svetlin.Nikolov]

True, the FLIP solver is the default for the Liquid sim. Only old scenes which contain the mixed simulator (PHXSimulator) will have the ability to use the old solver.

The new help is still being prepared and the nightly help is only up-to-date mostly regarding fire/smoke.

[joconnell]

I've got a very specific need to use phoenix for some blood bits, particle based emission seems like a better idea than what I was doing originally but there's some odd things here too, largely down to me being very new to the product. Can I set up a post on the beta forum to keep all the nightly stuff there or is it better somewhere else?

[Svetlin.Nikolov]

Yup - beta forum is the more proper place, although quite often nightlies are discussed here too.

[joconnell]

Off we go then