SOLVESPACE -- parametric 2d/3d CAD

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What does this redness mean? (It's not a medical question I promise XD ) (by Sean)
I've found three kinds of redness that SolveSpace uses to indicate things:

• Unsolvable constraints (dark red background)

• Unclosed 2D contour in sketch (red two points and line showing the gap)

• And this one I don't see in the reference docs that happens upon Extruding sometimes. Could someone explains what SolveSpace is trying to tell me with these thick red line and point indicators?
Sat Sep 18 2021, 20:48:13
(no subject) (by Andrew)
That redness indicates a problem with the solver/NURBS surfaces. One workaround is to use the 'Force NURBS surfaces to triangle mesh' in the properties window.
Sat Sep 18 2021, 21:13:59
(no subject) (by Sean)
I was only using lines and circles though; do circles count as NURBS's in this context?
Sun Sep 19 2021, 18:13:26
(no subject) (by Paul)
All surfaces are NURBS surfaces. The red lines indicate a problem finding the closed perimeter of a surface (or something like that). The red faces are actually the inside of a surface - probably visible because a different surface isn't shown due to the problems finding correct perimeter.

All groups should produce valid NURBS surfaces, the problems usually arise when a new group is combined with the previous geometry.
Sun Sep 19 2021, 19:03:53
(no subject) (by Sean)
Ahhhh I see, thanks!

So was it a bug or did I do something wrong?
And if the latter, for the future, is there a way I could have determined (before I spent all the time making that sketch) that it wasn't going to work?

And Aha! I recreated it and checked that it affected both rendering and "exporting as triangle mesh", but if I used "force NURBS surfaces to triangle mesh", then both rendering and "exporting as triangle mesh" did work after all and didn't leave out any faces!

(That's hilarious to me that "forcing to triangle mesh" isn't done when it's "exported as triangle mesh" but I know how things like that can happen in code haha)

So my only question is, does "force NURBS surfaces to triangle mesh" have permanent effects on the design or can I just turn it off later with no lasting effects?

(Oh and I guess also..if you only export to a .stl or .obj or other polyhedral/triangular model..does it even matter? I mean it seems to matter to SolveSpace because whole faces are missing haha, but I mean does it actually make anything less precise if it's ending up as a triangular mesh anyway?)
Mon Sep 20 2021, 18:07:39
(no subject) (by Paul)
It's a bug. Each new 3d solid (actually a shell) is created as NURBS surfaces and combined with the previous NURBS geometry. After the last group it is all converted to triangle mesh for display or export as triangle mesh.

If something goes wrong with combining the NURBS models you can force to triangle mesh at that point and it will often "fix" the problem. From that point on, new groups will be converted to triangle mesh and combined with the previous triangle mesh. When you do this it's no longer possible to export a STEP file for example because the NURBS are broken. The triangle mesh will also be less pretty, as combining triangle meshes using boolean isn't as clean as doing the booleans as NURBS and letting it convert to triangles after. Meshes are also slower and also have some bugs (different ones than the NURBS).

There is an icon on the text window toolbar to show the triangle edges in green. Use that to see the difference between NURBS and converting to triangles early in a complex model. And yes, you can switch any group back and forth without permanent effect on the model.
Tue Sep 21 2021, 17:16:29
(no subject) (by Sean)
I see!

Thanks so much for all your answers! That takes care of every single concern I had about this haha.

I don't think I've ever interacted with such a helpful forum :)

Thanks again.
Wed Sep 22 2021, 15:06:11
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