# Farmfield

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1. ## Particles trail from moving object (coming from 3ds Max)

You are thinking all wrong here. You're not emitting a trail, you are emitting particles that fly away with random directions and then adding a trail to those. If you want a trail from something, you can actually just ad the trail SOP, no need for particles at all. SOP.trails.hiplc
2. ## How to dampen FLIP particles using a falloff?

To keep it fluid-looking/behaving, viscosity would work well over the transitions and it's pretty easy to setup with a SOP solver and an attribute transfer.
3. ## Pyro - colour smoke by age

As smoke diffuses, age is basically the lessening of density, else I would presume you would have to use an intermediary for storing it, like a particle.
4. ## Small scale FEM

Yeah, this is probably one of those situations where simulating at the correct scale might be impossible and you have to sim it at a larger scale, tweak the time factor to get it looking the right scale... You know the drill, in the end it's all about how you/director/producer want it to look, not how it would look if it was real.
5. ## Ship Wave Trail

A ship wake is due to a combination of things, but as there is a low pressure zone behind the ship, the velocity is not directed backwards but inwards, downwards, behind the ship. Then you have layers of waves on top of that. Here's an illustration showing the main components in the wake.
6. ## Wax melting, candle burning

You gotta up the values, this is a flip sim.
7. ## Wax melting, candle burning

For the base you just need to up vescosity untill you get a solid, but for the melting part, you probably need to do a setup where the vax melts later, but faster, but make it solidify later, slower... That's the weird thing with candlewax, it's hard all the way up to the point where it just melts and becomes almost like water, but then it takes a long time to cool down. It's basically a bad heat exchanger.
8. ## Working on a nuclear explosion..need pointers, file and pic included

There is absolutely no need to do that high res simulations for good results and I'm pretty certain those 9 TB is the total disk space used including RnD and tests, not just for the final sim...
9. ## Working on a nuclear explosion..need pointers, file and pic included

I'm in no way critiquing any work shown in this thread, I just wanted to share what I believe is the best CG reference out there. As you should, imo, at least for the main explosion and the ground effects. Setting it up as one sim will force you into tweaking hell, as well as being less controllable, in production you would never do a setup like this as one simulation, it would be a disaster.
10. ## oil fire

One of the "problems" with the PyroFX solver is, it really, really enjoys looking like an oil fire, so this is likely one of the easiest looks to achieve with Houdini... And this tutorial from Carlos Parmentier is a good place to start in regard to messing with the PyroFX shader.
11. ## Working on a nuclear explosion..need pointers, file and pic included

So I just ran across this on Vimeo. This is about as good a setup I ever seen. Before this one, the setup used done for the Russian film "Ispytanie" ("The Test") was my personal Houdini-nuke favourite... Oh, and on a sidenote, "Ispytanie" is pretty cool as it's a 1 hour, 46 minute movie, but has no dialogue at all. But it's at least has a big boom.
12. ## How can I get Velocity Point run around the line

I did this setup and there's a link to the scenefile in the Vimeo description. Edit: Here's the direct link to the scene: http://www.dropbox.com/s/97ono7u8qq7zmm0/simple_vortex.hiplc

14. ## cracking a ground

@op For the ground breaking, I would go for a non simulated setup as in a real world situation, that's likely something the supervisor/producer/director will want to have complete control over, so I'd go for a map based approach for the growing cracks and for the main pieces I would animate manually. Then I'd do a separate secondary simulation for the crack center and finally a sim for pieces breaking off the edges. And I'd have that completely set up, simmed and baked out before I got started on the house, vegetation, etc...
15. ## cracking a ground

Hehe, how can you do that in reverse? The ground movement is what drives the house tearing apart, so you really can't do that backwards, unless I missed a workaround for that type of thing in some temporal mechanics course back in the day...
16. ## Viscosity "Shell" - Don't update attribute

Note you have to change the FLIP source type to particle field when you do the setup as I have now, converting it to a point cloud (as the FLIP source is defaulting to SOP surface). Also, though I didn't do that now, you should copy/paste relative reference between the points from volume and FLIP object particle separation, then the FLIP source will just use the input points without having to resample the source point cloud.
17. ## Viscosity "Shell" - Don't update attribute

Just create the viscosity before the sim. Viscosity_Shell_fix.hiplc
18. ## flip fluit to ice frost

There are a multitude of ways to achieve different types of growth type effects in Houdini, particles and/or SOP solvers are the first to come to mind. Here's a breakdown to get you started. http://ihoudini.blogspot.se/2009/05/growing-objects.html
19. ## cracking a ground

@OP Doing a setup like this in one go will guarantee you getting stuck in tweaking hell, so you'd split it up and do it in "layers". What you split into layers and in what order you simulate it depends on the scene, but here's an example based on the clip you linked to. And for every step here, you'd of course bake the animation/simulation for the previous layer. First you set up your foundation for the ground cracking, moving, be it animation or simulation. Next you simulate the secondary effects for the edges, etc.. Now you simulate the house on top of that setup. Finally you simulate additional objects like vegetation and such.
20. ## Cloth + RBD Interaction - Is it possible?

Also, for some solvers you gotta set it up for correct two way interactions, like, say you want FLIP fluids to not only collide with but be able to knock over a RBD object, in the FLIP solver -> volume motion -> solver tab, you need to set the feedback scale to 1 - the default setting is 0 - else it will not calculate the particle collisions from the RBD side in the DOP. And this is of course to save calculation time when doing simulations, no need to calculate this type of interactions as, most of the time, these effects are either not something you want/need or you'll set it up in layers and sim one thing after another, for control. In the end, having this type of interactivity between the solvers is cool, but it's often very hard to control the end result and you'll end up in tweaking hell...
21. ## Houdini -> V-Ray

There's a lot of VRay bugfixes popping up in the Houdini journals (the changelog) nowadays, so no question it's under heavy development.
22. ## Is it possible to implement full GPU based solvers inside Houdini?

Another issue with GPU acceleration is VRAM, I mean, in my experience (running a GTX970, 4Gb), you really don't need to run that big a FLIP sim's before you get out-of-memory issues, same with grains... But all this talk might be redundant anyways, a few weeks back I tweeted Gridmarkets asking them about supporting the H15 distributed simulations and I got a message back saying it was an awesome idea and that they would look into it directly - that would be a game changer for freelancers like me, having the possibility to do distributed simulations in the cloud. I used cloud rendering for years and nowadays I couldn't live without it.
23. ## Is it possible to implement full GPU based solvers inside Houdini?

I think this is in part about OpenCL being a mess while CUDA is unpopular to use. And I think it was Jeff Lait who wrote here a year back or two that there really wasn't much possible to GPU accelerate in the current solvers and that even the current OpenCL acceleration really only helps on a small part of the calculations in FLIP and grains...
24. ## get rid of mushroom effect in explosion and add details in the opening

Awesome share, Pavel. Much appreciated.
25. ## Exporting Houdini Particles to Maya

WTF is this BS? So Nuke and Fusion opens the Houdini (particles/points only) alembic files without any issues but Maya just don't import particles/points it seems. Also tried cleaning the attributes - and when that didn't work - even tried copying an add node point onto each particle so it's really stripped of all particle related attributes, but no difference. No clue what is going on. Importing Alembic meshes works great though.
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