Scene Scale

[hunter_williams]

I just wanted to confirm that if I am simulating something (water) and my boat is in the correct scale (whether it's meters or centimeters), the Grid Scene Scale value of 1 would be correct?

[hunter_williams]

I guess it does make a difference:

Grid scene scale: 0.118 (meters is unit in Maya)


Grid Scene Scale 1.0 (meters again):

[Svetlin.Nikolov]

Hey,

Check the info on Scene Scale here: https://docs.chaos.com/display/PHX4MAYA/Grid

This is the important part that concerns your question:



To put it in other words - as you change the Scene Scale, this info in the Total Cells box would update - check if the sizes there correspond to the real world size of the simulation that you'd expect - if not, then adjust the Scene Scale until you get the size you know is correct.

Cheers!

[hunter_williams]

The Rough Sea example had the scene scale at 0.118 (21.87m x 37.7m)

I created a plane with those same dimensions (much smaller)


If I change scene scale to 1.0 (186m x 320.9m)

Plane is now the correct scale to the ocean:


So, if I change the scene scale to 1, would I have to make some adjustments to Sim settings to make the water look like it is with scene scale 0.118?

Does it even matter?

Maybe I'm just being too anal about scene scale thing (I just like everything being real world scale).

[Svetlin.Nikolov]

So when you create a brand new simulator, the Scene Scale option is 1.0.

This means that everything in the simulation would react according to the real-world dimensions of the simulator in the scene.

However, if for some reason you need to cheat this, you can use the Scene Scale option to make the simulator THINK it's larger or smaller than it actually is.

For example, when imported geometry is not the correct scale and the scene is already built around it and can't change, you could use the Scene Scale option to correct this and make the simulator behave appropriately.
Or, as another example, in order to make a shot more epic, with slower motion and a more cinematic feel, you could also artificially raise the Scene Scale option.

As you change this option, the label in the Grid rollout updates with the grid dimensions the simulator thinks it has, so as you adjust the Scene Scale, you can keep an eye on these dimensions and make them the way you want. For example, if you have a scene which is 1m x 1m wide, but you want to have a volcano simulated in these confines, you could increase the Scene Scale option until the Grid rollout label shows that the Simulator thinks it's 400 meters tall

Does it make sense?

[Svetlin.Nikolov]

If we need to go into more details, the Scene Scale affects the gravity, and most of the other options it affects are more relevant to the Fire/Smoke simulations - for example, with higher scale the Temperature Cooling acts more slowly, the Smoke Buoyancy and the Fuel Buoyancy are slower, etc.

However, options that are in some world units in the user interface, such as the Foam Rising Speed, or the Foam Size - they will not be affected by the Scene Scale cheat - they will be just as large as the option says, otherwise it would be confusing to have to go through the multiplication in your head for each of these.

[hunter_williams]

I understand now. Higher values will produce slower looking simulations and vice versa. Scale of 1 is real world scale.


My question is, if I want to have the scene scale of 1 on this Rough Sea example, what values do I need to change to get it to look correct?

Is it the Ocean texture connected to the wave force? The displacement Ocean texture?

There are so many settings!

[georgi.zhekov]

Ah, as Sveltin mentioned - make sure that the simulator size is in the correct scale.
From then on there are two ocean textures - one for the WaveForce that will control how the simulated waves will look and another one hooked to Displacement that will give you the finer detail over the liquid mesh.
You can adjust the Ocean texture scale either though the Placement node or through the Wind Speed parameter in the Ocean tex options. So both should be in the correct scale and this should be it more or less.