10m prim diameter max?

I am a newbie building his first house, which happens to be octagonal. In the spirit of prim economy, I intended to use two flattened cylinders as the floor and the roof of the house -- but when I came to build them, I found that SL wouldn't let me extend the diameter of the cylinders beyond 10m. This is too small: I need them to be at least 50% bigger. My only other neat option now seems to be to make a floor and a ceiling which each consist of eight segments. This would result in 16 prims as compared to two, which would presumably contribute to a bigger load on the server than would two single slightly larger prims. What is the reason for this restriction, and is there any way around it?

Ten meters is the maximum size for any prim. Why? Dunno. I think it's related to the number of meters that sims overlap at the edge or something.

A bigger prim would be nice, but is currently impossible.

I'm curious how you were planning to make an octagon out of cylinders. A texture perhaps?

Anyway if I'm reading you right, it sounds like you want your octagon to be somehwere around 15 meters across. An octagon 15 meters across can easily be built with 6 prims. You don't need 8.

An octagon has .414 units in each side for every 1 unit in width. If yours is 15 meters across, then your sides should be 6.21 meters. To make your floor, start with 2 rectangles, each 6.21 x 7.5. Put them side by side so they create a single plane, measuring 6.21 x 15. Now make 4 more rectangles, each measuring 4.395 on Z x 7.5 on X. Rotate these so they lay flat, and then scale their tops 42%. Skew two of the tops to .29 and the other two to -.29. Line them up, and you have a very nearly perfect meter 15 wide octagon. (It's very slightly off, but it's as close perfect as you're gonna get with only 2 decimals to work with in the top scale.)

Anyway, I believe the size restriction is Linden's way of cutting down on prims overlapping sim borders. I don't really see how 10 meter objects are less likely to overlap than 20, 30, 50, or any other number, but that is the most common explanation.

Thanks, Cubey and Chosen, for your replies. Chosen, I wasn't intending to make an octagon out of cylinders: the walls of the building form an octagon, and I just wanted to use two flat discs slightly larger than the octagon as the ceiling and the floor. (This would have had the advantage that I could have made the floor cylinder hollow by a small percentage, giving a hole in the centre to provide access for my planned elevator -- the building is raised on stilts.)

What I've done now is to make two octagons out of eight triangles each. If I'm desperate to gain a few more prims, I'll try your way, but the eight triangles look nicer given my wood-grain texture than I suspect your rectangle arrangement might.

Thanks again for your help. Given both your comments, maybe we should lobby for bigger prims!

Just so you know, if u want a circular ceiling and floor, you can still do it. You actually can make circles of any size you want simply by cutting and squashing cylinders into arcs. For example, if u take 36 cylinders, each 10 M wide, cut them in half, and shorten them on one axis so they only bend 10 degrees instead of 180, you can make a circle over 100 M in diameter. Your 15 or 20 meter circle is not hard. It may be a little bit prim heavy, but it's certainly doable.

I've found the easiest way to do it is to use a texture as a floor plan and just build right on top of it. If you want a 20 meter diameter circle, just put a circular texture onto four 10 meter planes, and set the repeats per face to .25. Offset each one the proper amount to make them line up and appear as one. Now you have a 20 meter circle drawn out for you and from there it's very easy to line up your cylinder arcs on top of it. Once you've got them laid down, fill in. the area with rectangles, triangles, and half cylinders. Like I said, it's prim heavy, but it can yeild nice results.

Where there's a will, there's a way, always.