Hollowing a Prism

I dont particularly want to go to the effort of fitting four triangles together to make a pyramid ( three sides and a base) but it seems to me that the hollowing of a single prismatic prism is limited and doesnt seem to increase the interior volume as much as hollowing a sphere or cube does.


Therefore I'm wondering if any ingenious builder knows any clever trick for increasing the amount of area that can be created inside a prism.

Im also wondering as a prism doesn't seem to be hollowed to anywhere near the same degree as other prims do if this is some sort of bug with the system.....

Why not hollow a cube and taper it at the top? I think that is what a prism is anyway.

If you feel that you get more volume from a cube this would be the obvious solution to me.

It would not be expected to have as much volume as a square cube because you would shrink the volume by making the top tapered.

nice idea but that way you get a five sided pyramid (four sides and a base) instead of a prism (three sides and a base)

if you hollow a cube to 95 degrees or 95 percent ( or whatever that figure represents) and then turn it into a prism through the object menu... you get the same amount of the prism hollowed if you'd created a prism in the first place.

a prism is a tapered cube actually or am i thinking of the other on the tools?

I hate to be awkward but it isnt

look again


a cube has six sides ( five when tapered ...a prism (or tetrahedron) has 4 - 3 vertical faces and a base if you like.

The prism is an oddball prim. It's the only one that is tapered by default, which is unfortunate because it often fools people into believing its shape is different than it actually is. In truth, it's a pentahedron, an honest to goodness triangular prism. But because the default for it is to have its top tapered, people tend to think of it as a tetrahedron, a purpose for which it is ill-suited, as you've discovered.

To make things more complicated, the prism, just like its cousin the ring, does not completely fill its bounding box along the X axis. This was a major goof by the Lindens. Quite obviously, it was done to force the triangular base to be equilateral when the XY dimensions of the bounding box are uniform. That's a rather ridiculous priority. Had they made the geometry extend the full length of the bounding box, just like they did with every other prim, both the prism and the ring would be far more useful, and much easier to maneuver and manipulate. But since they did it the way they did it, both prims will continue to be frustrating to use, usually more trouble than they're worth for the average builder.

Most people do learn that the hard way, just as you seem to have, Maelstrom, if that gives you any comfort.

If you want to make a tetrahedronal pyramid, the best way to do it is out of 4 individual triangles. These can be either prisms or tapered cubes. I recommend cubes, due to the aforementioned X-axis deficiency in prisms. If you use prisms, your pyramid will be more limited in size.

The prism is probably one or the least-used and most misunderstood prims in SL.

Triangular base, with three triangular sides. It can also be untapered to make a triangular column with a triangular top and bottom and three rectangular sides.

A "Pyramid" is just a tapered cube, like a cone is a tapered cylinder.

But the next one to the right is labeled "Tetrahedron", and that is the Prism - 4 faces, with a triangular base, not five like the pyramid.

And the observation of the OP is very much correct. Hollowing a prism to 95% results in much thicker walls than hollowing a pyramid or cube or any pther prim to 95%.

I tried several prim torture tricks, and could not make a prism with thinner sides, that would act normally.

So I guess if you want a thin-walled, hollow tetrahedron with an open bottom, you would either have to use three prims, or a sculpted prim.

Actually the shape Im referring to is the tetrahedron...unfortunately its called a prism in the object menu of the editing set up which doesnt help...

looks like Im going to have to consider linking triangles but considering its difficult to tell what sort of triangle youre going to get slicing up a cube its not that much easier...

why do i always get half quoted??
i said
a prism is a tapered cube actually or am i thinking of the other on the tools?

the other being the tapered box/cube..

When the API's related to the huge prims was left open there was a sudden spurt of people
creating new shapes of huge prims. Hmmmm...

Makes me wonder how hard it would be to fix the prism.

just a little math....a sine here a cosine there.. =)

I can't figure it out. But if you make the center cutout shape into a square, it will only allow you to hollow up to 70%.

So I think just adjust your build so that you can use a tapered square. Forget about the pesky prism

a headache here a headache there
(actually I like math LOL)

Theres no way the hollowing of the prism/tetrahedron - not the pyramid - is correct.

Look how much a pyramid ( 4 sides and a square base) can be hollowed in comparison to the tetrahedron ( 3 triangular vertical faces and a triangluar base)...

I wish Lindens would look at improving the lot of the builder with more shapes - a few precut triangles and polygons.....

I'd love to use tetrahedra in my builds they look so good sliced with different textures used on the faces...

But I think the hardest aspect of building in sl is cutting and positioning triangles thats which I normally use spheres and toroids.

The prism just cant be hollowed enough to provide a living unit.......

........unless youre mummified.

I posted advice a while back on how to make a "Queen Anne" turret roof. This method can be used to make perfect tetrahedral roofs as well. 120 degrees for a three-sided prism.

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