Big domes and spheres...

sweet

Excellent work, Stephen, I'm glad someone with the math is working on this. What language and platform are you using?

To answer your question, ShapeGen builds spheres as stacked rings of tapered box prims. The LSL and object communication issues are actually trickier than the trig. Thanks for the tip about the sculpty issue.

Heh, thanks - although I'm dredging up 3d maths and vector stuff I hoped I'd seen the back of years ago!

I'm developing on Linux, in C++. It outputs in plain ppm, which I then pipe through pnmscale then ppmtobmp, all part of the NetPbm package. It can also output .obj files, which has saved a fortune in the Generate-Upload-Tweak cycle.

Oddly enough, I've already solved the prim communication stuff - I wrote a land scanner which rezzed hundreds of tiny triangles, then told them exactly how to orient themselves into the shape of the sim it was in. It's been superseeded by another sculpty generator, which saves approx 499 prims per sim Trying to implement various triangle reduction algorithms in LSL was fun, though...

Somehow I remembered this topic, after I created these.

First I created the 4th part of the dome, and next a 4th' square-corner version.
In the middle is a 10*10 'normal' SL sphere.

Worked with a forced to 8*8 points sculptie, and fiddled with those points;
-> it wont 'blob' or change / show gaps when you zoom in and out from 32*32 up close; or 16*16 - 8*8 zooming out (LOD changing issue)
-> it gives those straight edges
-> Did a lot of tweaking in sculptypaint and photoshop to get the final result.
-> In the end I scaled the sculptmap nearest neahbour to 128*128 and uploaded it lossless

using a nurbs object could you avoid the math? jw.. just make a sphere and cut it? (then change however)

Seems like it would work anyway

It would work, but one of my aims was to make it so that a sphere could be built out of multiple copies of one or two sculpties, rather than lots of different ones. You can see in Cels picture that each "ring" uses polygons of a different shape, becoming more tapered towards the poles. In my last picture, the big sphere is made up of 24 identical sculpties, for example.

To do what I wanted, you need to look into geodesic domes and the math behind them. They generate spheres using self-similar panels, rather than rings of trapezia. And I chose to write code to generate them, rather than messing about in a 3d package, because I work better that way.

In fairness, I now understand the math involved. But I also know the math behind NURBS and other splines (I've got a spline curve creator written entirely in LSL, and a Cardinal spline path follower, for example).

But, as usual, I never actually finish anything off!

Nifty stuff

I think though that any sculpties used will have to be specific to a certain desired size of sphere. On a single sculpty, one would be able to detect the curvature of it, which should in principle determine the size of the entire sphere.

It would be really nice to be able to generate some set of sculpty parts which could be used to build larger structures, but it's hard to see what a usefully small set of sculpty parts could be.

Well, you can always scale the sculpties down to make the sphere smaller, You'd have to re-do the math to position each one though (or write a script to do it).

Apart from spherical sections, the other obvious one is extruded arcs, to make larger turrets and towers. Anything less regular would probably need bespoke sections.

Why not grab the whole build and mass-stretch it?