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Looking for the most simple "skybox"


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Kenbro Utu wrote:


Kelli May wrote:

Rez a prim, size to 30m cube, hollow to maximum. Copy and rotate 90 degrees on the y-axis.  Congrats, you have the most basic room available. TWO PRIMS!.

Now convert to convex hull -- ONE PRIM!

Naughty!  (The convex hull of a hollow cube is a not-hollow cube. So I suppose it's still in the running for "the most simple 'skybox'" because it's one that can never be cluttered with avatars inside.)

[ETA: I actually meant to add something potentially useful: For some meaning of "most simple", a single 8-faced mesh model would beat anything you could do with prims here. Not sure if it would have a Land Impact of 1 at scale, but it would be simpler to render, at least.]

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If you link 6 prims and set them to convex hull your box will have 3 LI. Thats easy to texture and of course you can have windows. Just paint them on the wall texture.

If you use anything hollow - mesh or prim - you will not be able to use the prim saving convex hull setting of course and a mesh will require a proper physics shape. Not worth the efforts here so use prims.

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To fulfill your "most simple" and "LOW PRIM" specs, it's a hollowed cube for the walls with a 1 prim ceiling and a 1 prim floor. It doesn't come any simpler than that. That's 3 prims. Forget about setting anything to convex hull if you actually want to be inside the room and use stuff inside it as normal. Just link them together as normal.

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Parrish Ashbourne wrote:

or you can link 3 prims,

one box for the floor, and one box for the celling, both set to convexhull,

and a third box hollowed out for the walls set to prim.

total LI of 2

If you need help, let me know I can help you inworld, or send you some landmarks, or add some link here.

 

I tested that idea and it doesn't work. No matter which prim is used as the root, the object always ends up as 3 LI.

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Right; the mistake was linking all three together. Instead, one can link the floor and ceiling prims and make them both convex hull, then leave the hollowed-cube "walls" prim unlinked, and end up with the land impact of 2 instead of 3.

But then you still end up staring at the inside of a hollow cube, which can never be properly textured.

Maybe I'll break my own rule and fire-up Blender just long enough to find the land impact of a minimal hollow box. Or maybe not. It's not terribly practical, even if it happens to save one LI. On the plus side, each inside wall can get its own texture, but I'm sure it would have all the cam control drawbacks of a regular hollow cube prim, plus the unpredictable destination of objects one tries to rez on the surface of any mesh. (Could it be that this latter problem isn't known to the Lab?)

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I didn't bother with linking the roof and floor together and leaving the walls seperate because that's not what I think the OP meant by a room. I assumed he meant a room as a complete object. Still, he has some possibilities in this thread so, if he reads it all, he'll get what he wants.

You're welcome to mess about with Blender but it wouldn't satisfy the "simple" criteria even if it saves 1 LI :)

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I would like to know what problem the OP is trying to solve. Like a lot of posters said, a floor prim, a ceiling prim and a hollow cube between them does the job. This requires almost no building skills. However, if the idea is to save prims, maybe we are looking in the wrong place.

The hull of a simple skybox has a low land impact (from 3 tot 6 prims). I think what's inside matters, i.e furniture and the like. Old furniture (all prims) has a high land impact, when sculpties and mesh came, land impact of furniture went down a lot. In short I think it would be more productive to look for low impact furniture then to try and save a few prims on the outside of the skybox. 

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Phil Deakins wrote:


Parrish Ashbourne wrote:

or you can link 3 prims,

one box for the floor, and one box for the celling, both set to convexhull,

and a third box hollowed out for the walls set to prim.

total LI of 2

If you need help, let me know I can help you inworld, or send you some landmarks, or add some link here.

 

I tested that idea and it doesn't work. No matter which prim is used as the root, the object always ends up as 3 LI.

I had tested LI before posting and had a LI of 2, but that was not scaled up, so I retested today and some thing looks very wrong.

0.5x0.5 =LI2

6x6 =LI 2

7x7 = LI12

9X9 = LI 10

25x25 = LI 5

64x64 = LI 2

I tested on current firestorm and the current LL viewer, on LeTigra and the main server.

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Your'e right. That does look very wrong. My test was with 3 x 0.5 cubes - one hollowed and the other 2 flattened but not toally flat. And all I could get was 3 LI.

You could try the same test but going up in multiples of 8 or 16. It could be that, over a certain size, multiples of 8 or 16 make a difference. But my 0.5s got 3LI not the 2LI that yours got.

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Bree Giffen wrote:

I will combine all the replies and suggest making a skybox at 30x30 using the six prim method, link them and set it to convex hull. I have experienced many camera problems when using a hollowed out cube.

Yes. 6 prims linked and convex-hull'd is best.

Convex hull can 'warp' the bounding box at the corners - resulting in either falling through the floor or not being able to move all the way to the edges. So if you get too complex with you link to a convex hull things get weird. But I've use some hollowed shapes successfully.

- I think hollowing a prim, cutting away one side (for a U shape), and making that convex works. Been so long since I set up my build platform I forget if I set its walls to convex or not... :)

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A 2 or 1 prim alternative is to use 2 hollow cubes, each cutaway to make a squared U shape, and fit them together to enclose the room. Link them, of course. If you then set the object to be Convex Hull, it counts for just 1 prim, but you'll probably experience oddities inside it, and saving one prim/LI isn't worth it. Of course, your texturing is limited with this method. The inside surface of a hollowed cube is one face, and not a different face on each side. So with this method, you can have only 2 different textures on the inside - one for the floor and 2 walls, and the other for the ceiling and the other 2 walls.

If you do it that way, cut them (Path Cut) so that the ends are in the middle of the sides. That way you get nice 90 degree ends instead of the angled ends when you cut a whole side away.

ETA: I haven't tested this at full scale (30x30). Judging by the posts in this thread, a full scale one may not reduce to 1LI when set to Convex Hull. But if it's not Convex Hull, it will always be only 2 prims, regardless of its size.

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Phil Deakins wrote:

To fulfill your "most simple" and "LOW PRIM" specs, it's a hollowed cube for the walls with a 1 prim ceiling and a 1 prim floor. It doesn't come any simpler than that. That's 3 prims. Forget about setting anything to convex hull if you actually want to be inside the room and use stuff inside it as normal. Just link them together as normal.

 

My first skybox was built to that spec except that I used two hollowed cubes (actually rectangular solids, wider than they were tall) mated end to end, and the two end walls for 4 prims. I made one of the end walls transparent from the inside so I had a nice view, and I used a fairly bland texture from the Library—some kind of beige-ish plaster texture—for the interior walls. Even though all the interior surfaces had the same texture, in practice the effects of region lighting made that almost a non-issue; the ceiling was so much darker looking than the walls you really didn't notice that they were the same. I threw a couple of big rugs on the floor.

Architectural Design Award for Excellence. Or perhaps not ;-). Worked, though.

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This post really sums up what I like about building in SL, here we are talking about one of the most simple structures posable in SL, and there are many points of view on how and way it could be made or used one way or an other.

My sky box of choice is a sphere with a cylinder as a floor, with the floor a bit lower then center which helps with your camera in smaller spheres.

Now to figure out whats going on with land impact some thing is very wrong with it, not sure when this started, I just posted a question about this in the server forum.

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Hmmm....

 

If I just opened blender and made a cube, then made it hollow - and brought that into SL as a mesh object - how low could I get its land impact to be, and having so few polygons/vertices, would it suffer from mesh's usual problem of growing land impact if I scaled it up?

It seems like in doing this, I could get it at 1LI, and have better texture control - something to try.

 

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