Sinkhole with dirt on top

[reelinspirations]

I'm wanting to create a sinkhole effect, but not only use fractured geo, but I want to put a layer of sand/dirt on top so it looks more 'realistic.'

What would be a good way to approach this?

 

Thanks,

 

Jim

[anim]

sounds like a job for grain solver, or RBD + Grains together

[reelinspirations]

OK, that's what I thought, but I'm clueless as how to pull it off.

How do I set up a 'layer' of 'dirt' above my RBD fractured object?

I have a large area where I am creating several sinkholes. We're talking about 120 x 260 meters with sinkholes that range in size from 2-3 meters in diameter to around 20 meters in diameter.

I also have a ground plate (.jpg image) that I am 'flying' my virtual camera over. I know how to put a material on a piece of geometry, but how do I do that with grains?
Also, having a grain sim that large is going to kill my computer for a week :-) How do I only sim the sinkholes while keeping everything on the same level?

Thanks,

Jim

 

[anim]

you really need to start with small steps, get some reference of the effect you want to do and analyze what element it contains and how you can make them without necessarily going for the heaviest sim from the start

it's important to know the size of the effect in camera, if you will see 20m sinkhole just from far, then there is no need to go for Grain sim, just RBD for big chunks + lots of plain particles should be enough, maybe even just some geo deformation, with top layer of particles will look good

if you see closeup of the effect, then you probably not see whole 20m at the same time, so upressed grain may be ok, but still underlying deforming surface for the mass of sand may be very useful, so that only top layer is simmed

particles are no different from normal geometry so you can project uvs on them or rest attribute and texture as normal geo

 

[reelinspirations]

Good point Tomas,

The camera will be about 300' above the various sinkholes, so detail isn't as important.

So where do I find out how to create a 'layer' of particles 6" or so deep above my fractured GEO? 
Not sure a FLIP tank is appropriate. I'm quite new to Houdini, just a few months in.

I have the fracturing down and glue networks, etc. But it's the sand/dirt with particles portion I'm having trouble with.

I've included a portion of my 'background' plate that I need to use to create this effect.

How can I 'stick' this surface to grains for particles and how should I approach this.
Right now, I'm working on just a single sinkhole and trying to get the look down I want and be able to control it. But once I have that figured out, I'll need to figure out how to surface the entire thing with the background plate.

I know how to stick a surface on a box and fracture it, etc. But the layer of dirt on top makes things a little more complicated.

Thanks,

Jim

Edited May 16, 2016 by reelinspirations

[Adam Ferestad]

My personal favorite way of placing points like you are describing is to use a points from volume.  Just pass a closed mesh or volume to it and it will fill it with an array of ordered points.  If you need to randomize their positions, you can use the jitter in the node or a point wrangle to add noise to the positions in a more controlled way.  So basically you just make box that is over your fractured geometry, then convert the volume of said box to points.  I would assume that you would just pass the points to whatever solver you need.

I have not used the sand solver enough to be able to give you a good work flow with it just yet, but I would be really interested to see what you come up with.

Also, are you looking into using Pyro to make the dust clouds?  A friend and I came up with an interesting way of controlling pyro vortexes which I have been itching to use to drive some particles with.

[reelinspirations]

Thanks Adam,

I understand how to do the part up to the passing of the points to the solver. I am clueless on how to do that. I'd be using the pop solver because I really don't need grains unless I'm doing a CU shot.

Yes, I will be using Pyro for dust once I have the sim going. Would love to see your method.

Jim

[Adam Ferestad]

Jim,

Oh, that is actually fairly straight forward.  Here is a quick setup.

popFromPointsExample.hipnc

[reelinspirations]

OK, cool.
I'm wondering if I should approach this differently. What if I emitted a lot of particles from the broken pieces and copied some fractured geo to the particles and made them really small so they aren't just balls. Would something like that work?

I'm still trying to figure out how to have a layer of 'something' that will look like smooth dirt from 300' away and then be dynamic and fall away with the broken pieces.

Thanks again,

Jim

[carlo_c]

I had a go at the same effect you are trying to do (you can find it on my vimeo if you are curious to see it), I basically did what has been mentioned above. 

My process was to take the top layer geo, extrude it up, make a volume, fill it with particles, sim them to "settle", transfer my ground texture colour to it and then I simmed them with the collapsing geo. My PC at home could only handle so much so I used the upres tool after to get more particles.

I think if I wanted a thicker layer of dirt, I'd possibly try having my dirt layer as very small fractured geo pieces and then like you said emit lots of particles from those as they fall. That way I imagine you'd get a more interesting look of larger/smaller pieces.