To achieve the best results and the best performance with FEM, it is important that your input mesh is good quality. A mesh is good quality when its tetrahedrons resemble regular tetrahedrons and its triangles resemble equilateral triangles. A good quality mesh should also have no inverted tetrahedrons.
The FEM Validate SOP allows you to check your initial geometry before you send it to an FEM simulation. This node lets you:
Visualize the qualities of the primitives in your simulation mesh using color gradations between red (poor quality) and green (good quality).
Inspect the simulation mesh and identify any bad tetrahedrons, bad triangles, or inverted (according to the winding order used by Houdini) tetrahedrons on the outside or inside of your simulation mesh.
When importing a tetrahedral mesh from another package, its winding order may be the opposite to the one used by Houdini. If you encounter this, then you can use a Reverse SOP to correct the mesh’s winding order.
Limit the geometry that is to be validated to this group.
Allow choice between visualization of mesh quality and tet inversions.
Look at a slice of the tet mesh to see the tets on the interior.
A quality threshold value between 0 and 1; All tets and polygons below this value will be colored red, all above are colored green.
Isolate Primitives Below Threshold
Show only the primitives below the specified quality threshold.
The position attribute used to determine whether a tet is inverted:
Material means that the
materialP attribute is used. Current means that the current position attribute
P is used.
Show only the primitives that are inverted.
The origin of the clipping plane.
The distance of the clipping plane from the origin in the direction of the normal.
The normal direction of the clipping plane.