Visualizing rho and u in Paraview

[aiotko]

Hi,

I just wanted to start by saying thank you so much for sharing your project - it's really impressive!

Sorry for the beginner's question, could you please advise the way how to visualize rho and u in Paraview to get the visual picture like in Interactive Graphics mode?

I've tried using Contour for rho and Glyph for u, but Glyph crashed Paraview even with 80 Gb of RAM and Contour didn't look like the expectation )

[ProjectPhysX]

Hi @aiotko,

ParaView offers 2 Representation options for visualizing volumetric data:

• Slice: for velocity you can also select between Magnitude or X/Y/Z components
• Volume: for density you can also use Shade+Show Isosurfaces

Unfortunately, ParaView can't do Q-criterion isosurface like my built-in rendering engine.

Kind regards, Moritz

[aiotko]

Thank you for your explanation, @ProjectPhysX,

I'm just looking for a way to visualize Q-criterion isosurface from VTK output by pyvista or vtk in Python or C++ to have a view like in your engine since it's pretty useful.

Maybe you have an example of how to do it?

[ProjectPhysX]

ParaView can't do Q-criterion isosurfaces out-of-the-box unfortunately from 3-component vector data. This is how it's implemented in FluidX3D:

• for each of 8 cells in a cube, calculate the Q-value from a 6-point stencil
• calculate vertex positions of up to 5 triangles with marching-cubes
• color triangles based on interpolated velocity/color/temperature
• rasterize triangles

You'd have to copy the part to calculate the Q-value for each cell to your C++ setup and run it on the entire grid on CPU; you can temporarily store Q-values in the lbm.rho data field. Then export it to .vtk and let paraview draw the isosurfaces - without coloring though.