Sphere primitive

[Philippe Hurbain]

I copy here a discussion between Travis and myself about sphere primitive. Question is - should we change this primitive?

I don't think it would have mattered in this case, but please be aware that LDView's sphere primitive substitution produces a sphere with geometry significantly different from the LDraw sphere file's internal geometry. (Enable and disable primitive substitution with this file loaded and wireframe mode enabled to see what I mean.) The three "edges" of the eighth sphere that is the basic sphere primitive sub-unit are the same in LDView's version and LDraw's version, but the geometry between the edges is very different, so will produce different results when viewed with primitive substitution on vs. off if geometry is intersecting the middle of the sphere. (Note that the 48/ version of the sphere was actually produced by me using LDView's algorithm, so that one exactly matches LDView's substitution when the substitution is kicked up two notches.)

About sphe primitive - wouldn't it be best to change primitive to match LDView primitive substitution version? I have always been annoyed by the warped quads in present primitive. Granted, a few parts would get weird edge lines at junctions with other elements, but at least it would no longer change with primitive substitution (16x resoluton at least).

[Travis Cobbs]

I'd be happy to provide the file (in the same way that I provided the 48/ sphere primitive). However, I don't think I should be involved in the discussion of whether or not it's a good idea.

[Philippe Hurbain]

I quickly checked a bunch of parts using 8-8sphe (almost sure there's an intersection somewhere...), the look is not bad using either viewing mode. So I'd suggest to go ahead and submit the updated 1-8sphe primitive. Part's tracker reviewers will validate (or not) by their votes.

My review of parts also show that it would be useful to create a "towball" primitive, specially constructed to properly join a R8 sphere to a R4 cylinder.

[Travis Cobbs]

I sent the file to Chris for posting on the tracker.

[Travis Cobbs]

The file is now on the tracker.