How to create ellipsoid?

[ikeji]

Moved from #182

How to create ellipsoid?

For example, FreeCAD(Which also use OpenCascade) supports ellipsoid that have 3 different sizes.

Can we have similar thing in replicad?

Thanks

[raydeleu]

There is indeed an ellipsoid function in OpenCascade:

https://dev.opencascade.org/doc/refman/html/class_i_g_e_s_solid___ellipsoid.html

To use this you should check if it is part of the javascript library opencascade.js. If not you are out of luck. Else you could try to write a new function to extend the capabilities of Replicad. I tried a similar thing in CascadeStudio but it is not simple. I managed to create adaptations of existing functions, e.g. look at how the sphere function is defined and adaot that to ellipsoid.

[sgenoud]

I think that the class you have here is for data exchange - I did not find a geometric primitive for the ellipsoid. Nevertheless we can use another representation to build this. I need to add the primitives to the oc build, but I think I can achieve this, following this high level FreeCAD script.

[raydeleu]

I searched a bit more and found this statement (however I do not know the author of this statement):

"Ellipsoid primitive doesn't exist in opencascade.
So FreeCAD does a non-uniform scaling on a sphere.
The result is a rational BSpline surface, which is C0 continuous.
This is the reason for the GeomAbs_C0 warning that appears in BOP check.
A shape with C0 continuity is mathematically perfectly valid"

The class for ellipsoids that I referenced earlier is probably not usable for creating new solids (primitives).

Using the same approach as FreeCad would require a modification to allow for non-uniform scaling.