> (4) mesh #2
> This is an object, that cause strong artefacts per Rhino mesher.
> At MOI3D it looks much better, but maybe it's possible that the
> triangles can be avoided.

It looks like the object has a pretty complex trimming curve in some of its edges, which is having an effect on the mesh generation.

Here I have duplicated the highlighted edge off to the side and turned on its control points:



Compare that to the control points of the surface itself:




As you can see, the edge has a complex curve and it does not match the simple structure of the surface - that edge is not an isoparm of the surface even though it looks like it probably could be.

Edges have a big impact on meshing since to make a "watertight" mesh, the mesher has to produce additional points along each edge. A complex edge like that is going make it harder for pieces to get lined up and handled in the most simple way.


I've attached an updated version of your object here as mesh#2_quads.3dm - to simplify the edges of this shape, I took your object, used Edit/Separate to break it into individual surfaces, then selected all the edges of those surfaces and did a Delete to "untrim" them and get the natural surface isoparms as a new simple trimming boundary, and then rejoined.

With this better edge structure you can now get all quads when you export from MoI.


In general if you have high complexity edge curves or other irregularites in the geometry itself, it will often have some kind of an impact on not making the most ideal meshes from it as well.

- Michael