Bigger prims

Bigger prims

Here are some cool and useful Prim builder tricks.

Officially the maximum size for any object in Second Life is 64x64x64 m. On the Hypergrid and other opensim based grids, the limit is 256x256x256m.

There are "megaprims" in Second Life. These are old prims some content creators were able t create due to two old (and quickly fixed) bugs. The biggest of them is a whopping 65,536x65,536 m, big enough to cover 65,536 whole sims (In theory at least - they won't actually have any effect that far away from their root location).

But even without mega prims, there are ways to extend them beyond the official size. And in Second Life we also have the option to link two prims, force them over to the modern LI calculation and have them count as a single land impact combined.

I once posted a challenge in the Builders Brewery and later I reposted it on the official Second Life forum: How much land impact does it take to cover a whole sim completely with prims without using megaprims?

The obvious answer is 16 64x64 m prims but there are several ways to reduce it. I had four (or rather three-and-a-half) ways in my mind when I posted the challenge and two replies in the forum discussion came up with other solutions using scripts and - one of them - temporary objects.

I'll ignore the two scripted alternatives here since they're not really about prim handling (and also are quite heavy on the poor server). But my three-and-a-half answers are:

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Solution 1: Slightly smaller linked prims (11 LI)

As I said, you can use modern LI calculation to make two linekd prims coutn as only 1 LI combined. Unfortunately you can't do that with side-by-side 64x64 m prims because of the 54 m limit to the distance between linekd objects.

But you can link them if you reduce their size along one axis a little bit. 54x64 m is enough althoguh I usually prefer slightly less (50x64 m). Ten such pairs plus a sngle prim is enough to cover an entire sim, bringing the land impact down to 11.

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Solution 2: Top shear (8 LI)

Top shear is one of the prim twisting parameters and what it does is shift the top of the prims to one side, extending it up to 50% outside its nominal size.

Here are two such prims (colour coded for clarification), side by side and linked:

Between them these two prims cover as much ground as three unmodified prims and combined with Solution 1, they are still only 1 LI.

This way it is possible to reduce the total land impact for a full sim coverage to 8.

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Solution 2 1/2: Double top shear (? LI)

You can top shear along both the x and y axis to cover even more ground with a single prim. The problem is that you end up with rather irregular shapes and will have to overlap and/or add smaller filler for a complete coverage. Don't ask me how low you can get the LI this way. Thinking about it makes my head spin.

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Solution 3: Reverse taper (4 LI)

This is a bit special and needs a long explanation.

 Prims are "procedural" (aka "algorithmic") objects, that is the viewer is fed some basic parameters and generates the right shape according to those. As far as I can figure out, there are 14 bytes of parameters - give or take one or two, depending on exactly how the LL programmers thought at that time. That means there are 5,192,296,858,534,830,000,000,000,000,000,000 possible prim shapes. The software converting the prims to viewable mesh can generate all those shapes with no problems and none of them are harder or easier for it to handle than the others.

Most of those shapes are not available through the regular builder pallette or lsl though. They have been left out, some for obviously good reasons, others for more questionable ones. But after the viewer code was released as open source, somebody decided to take a closer look at this and added some extra functions to the builder palette giving us access to a few (but not nearly all) of those "secret"  prim shapes. These functions are still included in many third party viewers.

The parameter we want to look at in this particular case, is taper. Of course, tapering a prim normally means less surface area at one end of the path, not more. But it is actually possible to "reverse taper" it like this:

This prim is nominally 0.5x0.5x0.5 m but with "reverse tapering" the top surface is 1x1 m. Scale it up to max size and we get 128x128 m on the top, enough to cover a quarter of a sim. This is a legacy prim so the nominal land impact is 1. The actual LI can be a bit higher because of the physics weight but that's easily corrected by setting it to convex hull.