How to create a simulation grid with custom obstacles?

[sambaPython24]

Hey, thank you for your work and for your support on github!

In your examples pages, you show a nice example of how to create grids with custom obstacles, that are
created as boolean operations of boxes or how to load
a gmsh file as a grid.

Is there a more direct way of how to load a mesh for example by e.g. :

• Giving e.g. a boolean voxel mask of where an object is (e.g. True) or is not (False) or
• Loading a mesh consisting of e.g. vertices and faces (like for .obj files) without having to save it as a .msh file.

and - because I see only 2D Simulation examples in your code -

is that also possible for 3D Simulations?

[holl-]

Hi @sambaPython24 Yes, 3D is also supported.
For obstacles on a regular grid, you can pass them directly to make_incompressible(). Here is an example. Of course, you can also union them!

[sambaPython24]

Thank you @holl- for your quick answer and indeed I see the line
``fluid.make_incompressible(v, obstacle, Solve(x0=p))``` and that you have been creating obstacles using the predefined Cuboid and Spheres. In another tutorial, one could also upload gmsh file.

I assume, that you convert the Cuboid and Spheres to a part of a voxel grid at some point anyways, hence my question is wether I could just skip this step and provide this voxel grid directly (either as the simulation grid or just a binary grid with the location of the "blocked" voxel).

I have been trying to somehow change the objects

phiml.math._tensors.Dense
phi.geom._grid.UniformGrid
phi.geom._box.Cuboid
phi.field._field.Field

but it appears to be impossible to get or even change the underlying values in any way.

[holl-]

The reason you provide a Geometry or Obstacle object instead of a voxel grid is that the distance to the obstacle surface is also used in the computation.
If you only have a voxel grid, you can look at the experimental class phi.geom._voxels.Voxels, but this may not work for your use case.