Unit Setup

[psychoo]

Hello folks,

I have a noob question, does the system unit setup matter? My experience is, that when I use meters in system unit setup the simulation is quicker and more stable than when I do it in millimeters, regardless of the amount of cells and grid size. Is that plausible or just black magic?

Thanks
Barns

[flipbook]

Unit size is very important. I generally stick to CM and real world grid size. When I want to fake the scale I will switch to maybe 4m per unit or so for higher feeling scale stuff. All depends on the scale you are trying to get so that value is totally changeable for your individual scene.

Small scale liquid scenes do struggle as it is FLIP particles so I normally fake the unit scale but also steps per frame need increasing and introduction of surface tension helps.

It is all specific to the effect you are trying to achieve though.

[psychoo]

Thanks for your reply! I understand that unit setup is important but I wasn't sure how does it affect the parameters in the simulator. Apparently if you set your system units to milimeters, you have to increase your decimal precision to around 9 digits to start getting good results with foam, because you have to set your foam particle birth rate to 0,000000001. I think it is a pity, the simulator parameters should somehow convert internally to mean always the same for the simulation.

[Svetlin.Nikolov]

Hey

(This topic has been discussed many times here)
Basically, it's does not matter how you view your units - we should not be talking cm, meters, inches, etc. It matters if your simulator is as big as the thing you simulate. In the Simulation or the Grid panels of Phoenix you can check the dimensions of the container. If you simulate a camp fire, you should have a simulator that is a couple of meters wide. Or a couple thousand millimeters - it doesn't matter how you view it but what actual size it represents. If you put a volcano or a huge waterfall in a simulator a couple of meters big, it will not behave properly - you need to make the container several hundred meters long in order to it to look properly. Or this could read several hundred thousand millimeters - again, there is no difference - as you pointed out, the simulator should and does represent dimensions internally as world-space units, so what matters is how big a 3ds max unit is and how big the Phoenix container is - the way you choose to display the length is irrelevant.

Cheers!

[psychoo]

Thanks for your explanation. My problem now is that the faster moving parts of the boat generate too many foam particles, while other parts where the particle birth conditions are not met so easily produce too little foam. Maybe it would be nice to implement a limit to maximum number of foam particles generated in a cell. Maybe that would make it possible to fake the desired result.

[Ivaylo Katev]

can you share build details?

[psychoo]

Hi, of course:
2.25.01 Nightly Build ID: 1606046804

I managed to get quite good results btw, so it's problems due to lack of experience on my side.

[psychoo]

The hardest part for me is to make the seam disappear between the capped ocean geometry and the rest of the ocean surface. I use capped ocean geometry+a big, displaced ocean surface because then the reflections and GI is not messed up by the lack of ocean geometry behind the camera. Is there a good way to make the seam disappear? A setting to flatten out the simulated surface towards the edges of the simulator box would be nice for example.

[Svetlin.Nikolov]

This should happen automatically, can you share a screenshot of how it looks?

[psychoo]

Here you go

[Svetlin.Nikolov]

Ah, I see now. Will think about such setting, yes - it does happen with the regular ocean, so we have it as an available tool.

[Ivaylo Katev]

perhaps we have to add a checkbox "force dome camera", many users are rendering with cap+plane because the reflections and the consequent inability to use the regular ocean mode.
since we have dome camera support this should be easy to resolve

[psychoo]

That would be amazing!

[psychoo]

Fantastic software btw! I love it! Can't wait for the next version.

[psychoo]

I wonder why these waves appear on the sides? How can I get rid of them?