[ufocfd]

Is there a standard format for octree meshes in Paraview yet?
I notice there was not any replies to the previous posts on this subject.
I tried the octree.vto format with XMLHyperOctreeReader.xml,
but it does not allow slicing etc.

[ufocfd]

managed to do something using python script to
describe a load of box sources, but it takes ages
to run script and create the box sources for just

~400 boxes.

[flotus1]

Do you mean for displaying the solution from a solver that uses an octree-type mesh?
We use Ensight gold format with hexa8 element types for this puropse.
Works flawlessly in Paraview even for meshes with 100 million elements and more. Merging vertices at identical positions before importing into Paraview is key to performance here. I have no idea if this is the standard solution or even a particularly good one. But it was good enough so far.

[ufocfd]

Yes that's right. That's interesting thanks. I have achieved it using vtk unstructured mesh, but as you mentioned there are x8 duplicated mesh points which slows it down. How do you remove duplicate points?

[flotus1]

My algorithm goes something like this:
1) Calculate point indices using a space-filling curve, e.g. Z-order curve
2) Sort points according to this index
3) Go through the list. Every time the index increases, a new point is formed. Points that do not increase the index (i.e. sit at the same position as the previous one) are dismissed
4) Assign the remaining points to the cells in order to form the hexa8 data structure

[ufocfd]

Thanks very much for your thorough reply.
That gives me something to explore further.
Best wishes, Giles.

[ufocfd]

I managed to avoid the need for any point sorting/ordering by using a second octree for the points. I would call it a 'double-octree' method. You create the cell octree first then the point octree after. My new code generates 14 million cells & 19 million points in just 25 seconds. But writing to the VTK file takes longer ~8 mins. https://pbs.twimg.com/media/DlWsYt8XcAIP69J.jpg

[ufocfd]

Finally got F1 car demo testcase meshing 14.2 million octree cells in 48 seconds from start to finish, including VTK binary file write.

https://pbs.twimg.com/media/Dln9xWOXgAA1EH7.jpg