Second Life Forums Archive - bigger shapes for buildings

Jonathan Morris

Registered User

Join date: 5 Jan 2006

Posts: 66

07-11-2006 03:05

The biggest cylinder I can build is 10 m diameter.
A prim which was a "quater cylinder" would alow ( by grouping four if them ) a 20 m cylinder to be built, while keeping the 10m maximum prim size.
The same applies to a quater spere prim. a 20 m spere would be possible.

Is this an old idea.. or would it be worth asking the Lindens for these new prim types ?

Regards Jonathan

Lewis Nerd

Nerd by name and nature!

Join date: 9 Oct 2005

Posts: 3,431

07-11-2006 03:26

I believe the limits are set by the Havok physics engine (whether you are using them with physics appears to be irrelevant).

I too would love larger prims, it would make a lot of my building projects easier (especially those that are simple builds with textures, rather than lots of prim detail - because you can easily eat up those little allocations you have on your land.

I'd vote for it, but I think there are technical reasons why we can't.

Lewis

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Chosen Few

Alpha Channel Slave

Join date: 16 Jan 2004

Posts: 7,496

07-11-2006 07:37

I've posted this before, but here it is again, my guide to building large circles. The technique is simple, although it does take a little patience to get it right the first time. Follow the instructions precisely, and you'll end up with a cylinder 100M across. The technique can be adapted to make literally any size cylinder you want.

From: someone

Chosen's 7 Steps to a Giant Circle
It should take you about 30 minutes to do this the first time, and then you can take the circle into inventory. After that, it will take you all of a second or two to rez it each time you need to make additional cicles.

Lay out a circle texture across a large plane made of cubes. Use basic math to do the layout. If you want a hundred-meter circle, use a 10 x 10 configuration of 10M cubes. Set the texture repeates to 0.100 per face in both directions, and offset each one in increasing incriments of 0.100, starting +/-0.450 on each edge and +/-0.050 on the middle most prims. This way, the whole thing will lay out to form one complete image. (See Figure 1)
Hollow a 10M cylinder, and cut it down to 30% to make an arc. If you use any more than 30%, the edges will curve too much. I usually go with .35 to .65 on the cuts so that I'm working with the middle portion of the arc. This makes it easiest to manipulate.
Place the arc on the edge of the circle, and squash it until it's tangent at every point. For the size we're going for, 0.62 on X is about right if Y is 10. (See Figure 2)
Now for the tricky part. Duplicate the arc, and line up the copy by rotating it and moving it so that its edge is flush with the edge of the first piece, and so that it is tangent with the circle at all points. It should come out to be offset from the original by 9 degrees rotation, and by 7.946M on X and 0.6255M on Y (Yes, you can move things by more than 3 decimal places. Even though you can only see 3, you can type in well more than that.) (See Figure 3)

By the way, if you're wondering where I got the location numbers from, no, I'm not a trigonometry wiz. I laid the pieces by eye, moved the camera in as close as possible, and then increased or decreased the numbers in tiny increments until everything was flush. If you're better at trig than I am, I'm sure it's possible to just do the math and make the whole thing work automatically without having to eyeball anything.
Since we now know that 9 degrees is the magic number, we also know that it's gonna take 40 pieces to complete the circle (9 x 40 = 360 degrees). The good news, is we don't have to do anything 40 times. All we need to do is complete 1/4 of the circle, and then duplicate that quarter 3 more times. In other words, we only have 8 more arc segments to line up for a total of 10 in this quater, and then we're almost done. So, duplicate the arc 8 more times, and line them up. The rotation value for each one is obviously pretty easy, just increase each one 9 degrees. For location, again you can do the trig or you can just eyeball it like I do. (See Figure 4)
In figure 4, we can see that the circle is coming out a little too big. This is no big deal. It's just one of the effects of not doing the trig. Not to worry, it's simple enough to shrink the whole thing to the right size. The arc is still a quarter circle right now. It's just a quarter of a bigger circle than we wanted. Just select the whole thing and shrink it down a bit until it matches the circle again. Just make sure you slelect the original arc last, so that the whole shrinks in an easily controlable direction. It's also a good idea to take this opportunity to link the arcs as efficiently as possible. This will make things much easier for the final step. In this case, 2 groups of 5 works well. (See Figure 5)
Okay, we're almost done. All that remains is to duplicate the 1/4 circle 3 times, and line up the quarters to form a seamless whole. (See Figure 6)
(OPTIONAL) Cutting the cylinders leaves behind V-shaped crevaces on the inside of the circle where the edges of the arcs meet. To eliminate them, fill each one in with a triangular prim. I recommend using prisms since we're dealing with isosceles triangles, tapered cubes work just as well.

Or, a less prim-heavy alternative for filling the gaps is simply to overlap the arc pieces a little bit, rather than having them meet precisely at the corners. This makes the overall mathmatics slightly more complicated, but it works VERY well to eliminate the gaps entirely. Provided you use the right amount of overlap, your circle will appear to be totally seamless.

(Apologies that the mentioned attached images have been deleted from the forum server. The SL forums used to allow attachments, but now they no longer do. When I get around to it, I'll post the images on my website, and link to them, but for now the verbal description will have to do.)

Larger prims would be wonderful, of course, but they're not necessary. Anything can be built with the right combination of existing prims.

_____________________

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Land now available for rent in Indigo. Low rates. Quiet, low-lag mainland sim with good neighbors. IM me in-world if you're interested.

Warda Kawabata

Amityville Horror

Join date: 4 Nov 2005

Posts: 1,300

07-11-2006 07:42

The reason the prims are limited to 10m is to stop people from wearing 100mx100mx100m cubes on their heads just to grief. Older versions actually allowed much larger prims.

Ledje Gorky

Registered User

Join date: 1 Jun 2005

Posts: 126

07-11-2006 09:37

I'm not sure if most of you understand what Jonathan said exactly:

From: someone

A prim which was a "quater cylinder" would alow ( by grouping four if them ) a 20 m cylinder to be built, while keeping the 10m maximum prim size.
The same applies to a quater spere prim. a 20 m spere would be possible.

The prims would still be 10m , not bigger. (4 prims for a 20m cylinder)
Infact that would be an ingenious solution. (most buildings wouldnt need more then 20m anyway)

If you make this into a suggestion, you got all my votes.
(or even better, try talking to some Lindens)

BamBam Sachertorte

floral engineer

Join date: 12 Jul 2005

Posts: 228

07-11-2006 15:48

Take a 10x10x10 tube prim and do the following:
1) Give it a begin and end twist of 90
2) Make it 90 or 95% hollow
3) Give it a profile cut of 0.75 to 1.0
4) Play with the hole size Y to get different radii and height, leave hole size X at 1.0.
A hole size of 1.0/0.25 results in a 17m diameter cylinder that is 2.5m tall
A hole size of 1.0/0.50 results in a 15m diameter cylinder that is 5m tall
A hole size of 1.0/0.05 results in a 19.5m diameter cylinder that is 0.5m tall

The top and bottom edge will not be flat. If you need a flat edge then set the beginning or end profile cut to 0.875. This will reduce the height by 50%.

If you need a solid cylinder then leave out steps 2 and 3. The textures will look bad on the top and bottom unless you use planar texture mapping.

Sebastian Glitterbuck

Registered User

Join date: 14 Feb 2005

Posts: 23

Go to the Ivory Tower Library of Prims

07-12-2006 09:43

There are awesome tutorials that tell you how you make large circles and buildings using cross sections and other tricks. There are some amazing tips up in there.

Do a search on Ivory Tower, the sim its in starts with an "N".

seb

Loydin Tripp

It may be virtual but...

Join date: 28 Apr 2006

Posts: 150

07-13-2006 11:15

Chosen Few, thanks again, thank god there is some one out there just as crazy for detail

And got there before me, I often cut and paste your tidbits into PDf files for my library of all things Second Life.

No attachments? So much more could be communicated with images, this is a visual simulation environment is it not?

_____________________

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"No man is an island",
but I bought one anyway...

Norman Desmoulins

Grand Poohba

Join date: 10 Nov 2005

Posts: 194

07-22-2006 06:21

I read a Linden reason for the 10m prim limit (and 30m link limit) somewhere... the limit was applied because of issues on sim boundary crossing.

Dillon Morenz

Registered User

Join date: 21 May 2006

Posts: 85

07-24-2006 13:04

From: BamBam Sachertorte

Take a 10x10x10 tube prim and do the following:
[snip]

The top and bottom edge will not be flat. If you need a flat edge then set the beginning or end profile cut to 0.875. This will reduce the height by 50%.

This really is a fantastic tip...question about the non flat edges though. I noticed (as expected) texture flicker when I stacked two of these tubes. I actually overlapped them so lost a little height, but even then, a very thin line was visible. As it seemed to be the non-flat, overlapping edges showing through...I applied a transparent texture to them to resolve it. Wow. It worked! But did it? It seems too easy to be true. I'm assuming other people here have tried this? Is it a good solution? Will I notice problems later? In different light maybe? Or when other factors present themselves?

_____________________

Haravikk Mistral

Registered User

Join date: 8 Oct 2005

Posts: 2,482

01-05-2007 07:22

From: Norman Desmoulins

I read a Linden reason for the 10m prim limit (and 30m link limit) somewhere... the limit was applied because of issues on sim boundary crossing.

Correct, simulators (and since 1.10 occlusion culling) rely on the maximum size of 10m in order to determine when an object needs to be handled, for things like sim crossing etc.

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10gb DDR2 800mhz FB-DIMMS
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bigger shapes for buildings
Jonathan Morris Registered User Join date: 5 Jan 2006 Posts: 66	07-11-2006 03:05 The biggest cylinder I can build is 10 m diameter. A prim which was a "quater cylinder" would alow ( by grouping four if them ) a 20 m cylinder to be built, while keeping the 10m maximum prim size. The same applies to a quater spere prim. a 20 m spere would be possible. Is this an old idea.. or would it be worth asking the Lindens for these new prim types ? Regards Jonathan
Lewis Nerd Nerd by name and nature! Join date: 9 Oct 2005 Posts: 3,431	07-11-2006 03:26 I believe the limits are set by the Havok physics engine (whether you are using them with physics appears to be irrelevant). I too would love larger prims, it would make a lot of my building projects easier (especially those that are simple builds with textures, rather than lots of prim detail - because you can easily eat up those little allocations you have on your land. I'd vote for it, but I think there are technical reasons why we can't. Lewis _____________________ Second Life Stratics - your new premier resource for all things Second Life. Free to join, sign up today! Pocket Protector Projects - Rosieri 90,234,84 - building and landscaping services
Chosen Few Alpha Channel Slave Join date: 16 Jan 2004 Posts: 7,496	07-11-2006 07:37 I've posted this before, but here it is again, my guide to building large circles. The technique is simple, although it does take a little patience to get it right the first time. Follow the instructions precisely, and you'll end up with a cylinder 100M across. The technique can be adapted to make literally any size cylinder you want. From: someone Chosen's 7 Steps to a Giant Circle It should take you about 30 minutes to do this the first time, and then you can take the circle into inventory. After that, it will take you all of a second or two to rez it each time you need to make additional cicles. Lay out a circle texture across a large plane made of cubes. Use basic math to do the layout. If you want a hundred-meter circle, use a 10 x 10 configuration of 10M cubes. Set the texture repeates to 0.100 per face in both directions, and offset each one in increasing incriments of 0.100, starting +/-0.450 on each edge and +/-0.050 on the middle most prims. This way, the whole thing will lay out to form one complete image. (See Figure 1) Hollow a 10M cylinder, and cut it down to 30% to make an arc. If you use any more than 30%, the edges will curve too much. I usually go with .35 to .65 on the cuts so that I'm working with the middle portion of the arc. This makes it easiest to manipulate. Place the arc on the edge of the circle, and squash it until it's tangent at every point. For the size we're going for, 0.62 on X is about right if Y is 10. (See Figure 2) Now for the tricky part. Duplicate the arc, and line up the copy by rotating it and moving it so that its edge is flush with the edge of the first piece, and so that it is tangent with the circle at all points. It should come out to be offset from the original by 9 degrees rotation, and by 7.946M on X and 0.6255M on Y (Yes, you can move things by more than 3 decimal places. Even though you can only see 3, you can type in well more than that.) (See Figure 3) By the way, if you're wondering where I got the location numbers from, no, I'm not a trigonometry wiz. I laid the pieces by eye, moved the camera in as close as possible, and then increased or decreased the numbers in tiny increments until everything was flush. If you're better at trig than I am, I'm sure it's possible to just do the math and make the whole thing work automatically without having to eyeball anything. Since we now know that 9 degrees is the magic number, we also know that it's gonna take 40 pieces to complete the circle (9 x 40 = 360 degrees). The good news, is we don't have to do anything 40 times. All we need to do is complete 1/4 of the circle, and then duplicate that quarter 3 more times. In other words, we only have 8 more arc segments to line up for a total of 10 in this quater, and then we're almost done. So, duplicate the arc 8 more times, and line them up. The rotation value for each one is obviously pretty easy, just increase each one 9 degrees. For location, again you can do the trig or you can just eyeball it like I do. (See Figure 4) In figure 4, we can see that the circle is coming out a little too big. This is no big deal. It's just one of the effects of not doing the trig. Not to worry, it's simple enough to shrink the whole thing to the right size. The arc is still a quarter circle right now. It's just a quarter of a bigger circle than we wanted. Just select the whole thing and shrink it down a bit until it matches the circle again. Just make sure you slelect the original arc last, so that the whole shrinks in an easily controlable direction. It's also a good idea to take this opportunity to link the arcs as efficiently as possible. This will make things much easier for the final step. In this case, 2 groups of 5 works well. (See Figure 5) Okay, we're almost done. All that remains is to duplicate the 1/4 circle 3 times, and line up the quarters to form a seamless whole. (See Figure 6) (OPTIONAL) Cutting the cylinders leaves behind V-shaped crevaces on the inside of the circle where the edges of the arcs meet. To eliminate them, fill each one in with a triangular prim. I recommend using prisms since we're dealing with isosceles triangles, tapered cubes work just as well. Or, a less prim-heavy alternative for filling the gaps is simply to overlap the arc pieces a little bit, rather than having them meet precisely at the corners. This makes the overall mathmatics slightly more complicated, but it works VERY well to eliminate the gaps entirely. Provided you use the right amount of overlap, your circle will appear to be totally seamless. (Apologies that the mentioned attached images have been deleted from the forum server. The SL forums used to allow attachments, but now they no longer do. When I get around to it, I'll post the images on my website, and link to them, but for now the verbal description will have to do.) Larger prims would be wonderful, of course, but they're not necessary. Anything can be built with the right combination of existing prims. _____________________ . Land now available for rent in Indigo. Low rates. Quiet, low-lag mainland sim with good neighbors. IM me in-world if you're interested.
Warda Kawabata Amityville Horror Join date: 4 Nov 2005 Posts: 1,300	07-11-2006 07:42 The reason the prims are limited to 10m is to stop people from wearing 100mx100mx100m cubes on their heads just to grief. Older versions actually allowed much larger prims.
Ledje Gorky Registered User Join date: 1 Jun 2005 Posts: 126	07-11-2006 09:37 I'm not sure if most of you understand what Jonathan said exactly: From: someone A prim which was a "quater cylinder" would alow ( by grouping four if them ) a 20 m cylinder to be built, while keeping the 10m maximum prim size. The same applies to a quater spere prim. a 20 m spere would be possible. The prims would still be 10m , not bigger. (4 prims for a 20m cylinder) Infact that would be an ingenious solution. (most buildings wouldnt need more then 20m anyway) If you make this into a suggestion, you got all my votes. (or even better, try talking to some Lindens)
BamBam Sachertorte floral engineer Join date: 12 Jul 2005 Posts: 228	07-11-2006 15:48 Take a 10x10x10 tube prim and do the following: 1) Give it a begin and end twist of 90 2) Make it 90 or 95% hollow 3) Give it a profile cut of 0.75 to 1.0 4) Play with the hole size Y to get different radii and height, leave hole size X at 1.0. A hole size of 1.0/0.25 results in a 17m diameter cylinder that is 2.5m tall A hole size of 1.0/0.50 results in a 15m diameter cylinder that is 5m tall A hole size of 1.0/0.05 results in a 19.5m diameter cylinder that is 0.5m tall The top and bottom edge will not be flat. If you need a flat edge then set the beginning or end profile cut to 0.875. This will reduce the height by 50%. If you need a solid cylinder then leave out steps 2 and 3. The textures will look bad on the top and bottom unless you use planar texture mapping.
Sebastian Glitterbuck Registered User Join date: 14 Feb 2005 Posts: 23	Go to the Ivory Tower Library of Prims 07-12-2006 09:43 There are awesome tutorials that tell you how you make large circles and buildings using cross sections and other tricks. There are some amazing tips up in there. Do a search on Ivory Tower, the sim its in starts with an "N". seb
Loydin Tripp It may be virtual but... Join date: 28 Apr 2006 Posts: 150	07-13-2006 11:15 Chosen Few, thanks again, thank god there is some one out there just as crazy for detail And got there before me, I often cut and paste your tidbits into PDf files for my library of all things Second Life. No attachments? So much more could be communicated with images, this is a visual simulation environment is it not? _____________________ Loydin Tripp -in Lingua Franca "No man is an island", but I bought one anyway...
Norman Desmoulins Grand Poohba Join date: 10 Nov 2005 Posts: 194	07-22-2006 06:21 I read a Linden reason for the 10m prim limit (and 30m link limit) somewhere... the limit was applied because of issues on sim boundary crossing.
Dillon Morenz Registered User Join date: 21 May 2006 Posts: 85	07-24-2006 13:04 From: BamBam Sachertorte Take a 10x10x10 tube prim and do the following: [snip] The top and bottom edge will not be flat. If you need a flat edge then set the beginning or end profile cut to 0.875. This will reduce the height by 50%. This really is a fantastic tip...question about the non flat edges though. I noticed (as expected) texture flicker when I stacked two of these tubes. I actually overlapped them so lost a little height, but even then, a very thin line was visible. As it seemed to be the non-flat, overlapping edges showing through...I applied a transparent texture to them to resolve it. Wow. It worked! But did it? It seems too easy to be true. I'm assuming other people here have tried this? Is it a good solution? Will I notice problems later? In different light maybe? Or when other factors present themselves? _____________________
Haravikk Mistral Registered User Join date: 8 Oct 2005 Posts: 2,482	01-05-2007 07:22 From: Norman Desmoulins I read a Linden reason for the 10m prim limit (and 30m link limit) somewhere... the limit was applied because of issues on sim boundary crossing. Correct, simulators (and since 1.10 occlusion culling) rely on the maximum size of 10m in order to determine when an object needs to be handled, for things like sim crossing etc. _____________________ Computer (Mac Pro): 2 x Quad Core 3.2ghz Xeon 10gb DDR2 800mhz FB-DIMMS 4 x 750gb, 32mb cache hard-drives (RAID-0/striped) NVidia GeForce 8800GT (512mb)

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bigger shapes for buildings