Making an octagon

Is it possible to make an an object with an exterior octagon?

I know you can take two squares and rotate one 45o to make an interior octagon... I want an external one

--Jack Lambert

I guess you could just use 4 rectangular prisms (stretched boxes), intersecting their COGs at a common point, and each rotated out of phase on a plane by 45deg. That's not a very clever solution, though, is it?

I will maybe play around in a sandbox and post back if I get some results.

Well, here's an idea: it's not a perfect octagon, really, but you can take 3 elongated boxes, stacked along their long sides, and just set reduce the topsize of the first and last to pinch them (a value of 1/3 works well). It looks reasonable, and it also gets rid of the "overlapping textures that share the same plane" flicker-effect.

    ___
1  /___\
   _____
2 |_____|
   _____
3  \___/

For making a solid regular octagonal shape:

Let M = the height and width of the octagon as shown in Gene's diagram.

Set the width of prim 1 to M , the height to M times .2929, and one of the topsizes in the appropriate direction to M times .4142

Set the width of prim 2 to M and set the height to M times .4142

Prim 3 is like prim 1 but rotated 180 degrees.

The .4142 is the square root of two, minus one.

You can make any polygonal shape with Cadroe Murphy's shape maker.
It's free.

There is some ambiguity in the notion of "an octagonal shape". It could be a solid with emphasis placed on minimum prim use, which I think is what gene's idea implements.

One might want an hollow octagonal cylinder, for use as an octagonal building, for instance. Cadroe's shapemaker can make such a thing, but because it is designed to also make more complex shapes, it does not address the question of having both the interior and exterior corners meet perfectly. For a simple polygonal cylinder with sides no greater than 10 meters is is possible to use the topsize feature to make one with beveled edges on each face such that the faces meet perfectly with no overlap.

I made an octogonal tower using a technique I learned in game from more experianced builders i call "radial architecture"

The basic idea is you use a central prim and rotations to make it. I usualy start with a central square, drag a copy out from it (this way it is lined up) you drag it out exactly as far as you want teh radius of the octogon. This is a wall piece. Then I usualy drag a copy of it up, and then copy the Z coordinates of the old one and put it back at that altitude. then you essencialy have 2 wall pieces in the same spot. I thin select one, link it to the central prim, and rotate the root prim 180. You proceed as described rotating them to 45, 90, 135, etc all the way til you have 8. I think someone above described how to figure out how big they should be, im bad at math so I usualy just play with them untill they look right

I bet I just confused the crap out of you, but it works

Jack, I don't know if the ShapeMaker tool will do what you want, but I dropped one on your inventory so you could check it out if you want.

Thanks so much for all the help guys!

--Jack Lambert

Your post was mildly confusing. I independently discovered one such technique to make n-sided polygonal walls back in, say, october 2003 or something.
I used to teach it at my Advanced Building classes. It would be a pain to try to explain it here textually, but I will gladly teach it in-world to anyone interested, free of charge.

What Barnesworth was saying was:

set an object at center of build.
Make a wall piece, and position it where edge is wanted.
duplicate wall (or wall and center piece)
link wall and center piece
rotate center piece 360/(number of sides) degrees
un-attach wall/drop new wall at new position.
repeat rotation till all walls inplace


This gives the advantage of putting the wall-piece in the correct location, without havign to do ugly math for angles and offset from center

haha you said it much better than me, thats exactly what I was trying to explain, It is one of those things that is easier shown then said. If you want contact me in game sometime and I will show you, its actually rather simple - if I can do it anyone can lol.

Oh WOW!

I'm a rubbish builder and that is a fantastic idea!

I've been using the shift-copy (z axis) method for centering things on top of other things ... that's another cool idea!

--Jack Lambert

Hi Jack.

I dropped a pre-made octagon shape on your profile as well as my "hexaoctoquadro" prim from which you can make a variety of shapes by delinking and deleting prims as necessary.

The first octagon I sent you was no copy no mod, so I sent you a second one with all perms enabled. Enjoy.

Cadroe, I'm new here, trying to gather as many tools as I can to start 'creat'n shit'... could you drop me a copy of thate shape maker plz? Thanks!

Barnes, after the shift-copy up just hit Ctrl-Z. The copied prim snaps back to the exact same spot as the original, rather than deleting. This will save you a lot of time

I never thought of that. Thanks for the tip Brent!

While I found that making an octagon with a central object worked for me, I am now trying to taper the walls as they go up. So far, I have been unsuccessful. Can anyone give me a clue as to what to do?

Check out the Lighthouse store on FairChang Island. I made that an elongated octagonal building. Pheewww what a struggle. Garth helped with the tweaking. It is not hard to find as the Telehub landing is on the roof.

I am posting a picture of when I was building it on Tilitr before we had FairChang Island

How thick are the walls? Do they need to taper on the inside as well as the outside? For the most general solution, you have to do a lot of math. I built a hexagonal dome that way last year and it turned out fine. I've found that using rods to hide the seams looks pretty good.

If you only care about the taper on the outside, you can cheat a little. On your box prim, have an X size of say 1m. Reduce the X top size to 0, and set the X top shear to 0.5. Now you have a slanted wall. Reduce the Y top size to a number N. You'll have to do some trig to figure out N, because it depends on the X, Y and Z dimensions of the box prim, and I don't do trig to answer forum questions

I just made an octogon this weekend as my own experiment before seeing this.
I failed horribly.
Then I ran into Timeless Protocol and he showed me his product called builder tabs. Bought it and WHAM problem resolved. Was quick, simple and easy. BTW My octogon was made using 10x10 pieces, flat top, and bottom.

Don't forget, your chat window must be closed for this to work. Unless it was changed in 1.6, I haven't checked lately.

Hey, thanks for the plug (forgiving the surname error).

The Builders' Tabs Kit certainly does help build these kinds of shapes in no time at all - and more importantly without all the complicated maths! Once you have setup a single side, simply take it into inventory and rez as many sides as you need and then touch the tabs to assemble the final shape. One command will then cause the tabs and scripts to remove themselves from your final product.

Perfect alignment.

Sorry I spill like shet. English is also my 1,000,000 lnguage. When I figure out the other 999,999 I'll let everyone know. Besides I wasn't home to check the spelling. (

The interior angles of regular polygons are given by the formula ( (n-2) * 180 degrees ) / n where n equals the number of sides.
In the attached diagram the formula yields the angle I.

We can make a regular polygonal cylinder using topsize to adjust the value of angle J shown in the diagram, which is half of angle I, the interior angle of the polygon.

For an octagon the interior angle I is 135 degrees, giving us a half-interior angle J of 67.5 degrees.

The following code fragment, when properly placed in a script in an object , will set the angle J to 67.5., or other angles as needed for polygons with different number of sides.

Here is an example of the always popular 7 sided polygonal figure the septagon with corner angles set using the code above.