Slightly confused about exporting a sim

[stelees]

Hey there,

My daughter wants me to do a little render for her that is basically her name filling with a different coloured liquid in each letter and with foam.

What I want to do is each letter separately and then just import it back in to max to render out. I can see a few different articles about exports.. do I need to follow the Export to OpenVDB approach?

I was thinking I can use this also if I ever get the waterfall working properly where I can sim out single instances of multiple falls along a cliff face, then import them all back in and render.

Appreciate the help.

[joconnell]

Nope, the good bit about phoenix is that it'll just work with whatever is visible in the viewport. What you'd do is make the letters as individual objects, do a separate phoenix grid and fluid emitter for each and then sim them individually. Each grid you sim will only make use of emitters that are inside the grid so if there's letters that overlap you can use the scene interaction section to control which objects in your max scene are used. For your waterfall, you can do one sim and then either duplicate your phoenix grid like a regular max object or use the vray volume grid object to load in a copy of the phoenix sequence cache files.

Edit: Open vdb is if you want to transfer your sim to a different program, it's a universal file format for anything volumetric, like alembic for geometry or exr for images.

[stelees]

ok thanks for that. In relation to the rendering though. With the waterfall one.. Are you saying I just have one main phoenix source, then as many grids and emitters as I need.. i.e like you said.. sim one copy the grid and the emitter and move it down the cliff face and then sim that one.. when I render it all out they all just play back at once due to each grid have a different output?

[joconnell]

Yep - A phoenix grid is both a simulator and a loader - it'll keep sim settings for your scene and also shader settings to render with. When it's done simming, the results are saved as a single cache file per frame of your sim (.aur files = phoenix used to be called aura) in a folder beside your max file. Once these are on disk, the phoenix grid is just reading those files and rendering them. The phoenix grid becomes an object that you can move around your scene, each copy of it is going to load in the same cache files.

Another option is the vray volume grid (https://docs.chaosgroup.com/display/...VRayVolumeGrid) - it's the same as the phoenix grid except with no simulation features. It'll allow you to load in a phoenix sim cache and render it the same way, using the same shader settings you have in your phoenix grid too. You can mess around with the playback easily too so if you want to have your cache play earlier or later, you can set a different frame of your scene for it to start playing at.

[stelees]

ah yeh, the volume grid sounds the way. When I am rendering I just want the playback so wont need to tinker with anything and I am assuming the volumegrid will be a little faster also?

[Svetlin.Nikolov]

The volume grid is the exact same thing as the Phoenix Simulator, but with less settings - the speed would be exactly the same, and there are only a few defaults that differ (e.g. in the Atmosphere settings, probabilistic rendering is enabled for the volume grid by default but disabled for Phoenix).

[stelees]

ok so one last dumb question. Obviously it is too much of a drain to sim 4 different grids at once. So is the workflow here.. have a single phoenix source. first grid and emitter then sim. Copy that grid over to the next part on the cliff and rename the emitter and add to the source, then sim that one also. Once I am done with the grids, then basically just render away and let it churn?

[georgi.zhekov]

You can use either one big grid or a few smaller ones - no problem at all. One grid can work with many sources and emitters without a problem. Everything that is inside the dimensions of the grid will be simulated by default.

You can render even during simulation for testing purposes, if you press render while the sim is still running, the simulation will be paused until the render is finished and then continue from there.

Cheers,

[Svetlin.Nikolov]

Note that several separate simulators will interact with one another by default, so if you don't want that, you can go to the Interaction rollout and exclude them from one another, or even switch to include list and pick only the sources and obstacles a sim interacts with, so Max won't throw a circular reference error if you try to mutually put two simulators in each other's exclude list.

If you choose to go with one big grid, it's gonna eat up more RAM. The empty space in Phoenix liquid sims is not gonna take much extra time to simulate, unless you have air effects enabled under Dynamics - in that case, all voxels will be calculated no matter if they contain liquid particles, much like the way the grid fire/smoke solver works, where the velocities are crucial, no matter if there is any visible matter over them

[stelees]

Nah I wasn't going to go one big grid. I don't have the oomf to get that over the line anyway. I just want to do them one by one as they are pretty spaced out along a cliff face in this example, just want not kill my machine