Hi Martin,
quote:
The only thing that's still a little puzzeling, is that none of these artefacts seem to show in the Surface Analysis tools that are part of ViaCAD Pro. So does that mean it's just a display 'feature' rather than something fundamentaly wrong with the geometry? I include a couple of Zebra screen shots for reference.
It's most likely an issue with ViaCAD's surface analysis tools - as I mentioned before ViaCAD is just not creating a dense enough mesh to pick up on these ripples which are quite small in size.
But also on top of that zebra stripes by their nature are rather better at displaying how things connect at surface edges where there is actually a break in continuity. It's not so good to detect little ripples that are located within a single surface. Those ripples are actually not continuity breaks, the surfaces have full continuity throughout their interior areas.
It's easy to jump to the conclusion that full continuity also means full quality, but that's unfortunately something that many people are easily mistaken about - you can have full continuity but problems with bumps and lumps.
If you look closely in your zoomed in zebra analysis shot, you can see some of the jagged artifacts that are coming from polygon outlines:
Those polygons are larger than the little bumps, you're not going to be able to see the bumps unless you get polygons that are small enough so that they actually follow the surface more closely.
Even then Zebra is not really the best tool for looking for bumps, glossy specular highlights tend to be better for bump analysis but only if you have a dense enough mesh.
Also as I mentioned, those little bumps are actually related to the reason why the fillet fails in ViaCAD if you go even a little bit larger in radius - the next little bump up in size changes from a kind of awkwardlly bunched area into a full fledged self intersection which is kind of more traumatic.
If you backed off just a slight amount in radius probably those bumps would go away as it would avoid some of the bunching that is causing it.
But I'm pretty sure you've got those bumps in ViaCAD as well (with the radius set to just before it fails), you're just not able to see them because the display mesh is not fine enough even at its "super fine" level.
I've seen the same kind of problem (can't see tiny surface details due to coarse meshing) in other CAD programs as well, it's not particularly unusual. But one of the nice things about MoI's regular display is that it is detailed enough to be able to see those kinds of things.
- Michael
