Terraforming and Caves

Hi,

I have a few questions about terraforming and caves. From what I have seen it is possible to build a cave underneath the ground as the ground is not solid underneath the ground layer that you stand on. Is this correct?

Assumig the answer is yes, how can you "punch" a hole (i.e. cave entrance) through the ground layer so one can get to the cave? Is this possible or does one have to teleport to the cave?

Finally, if the land you are creating this cave on (underneath the ground) is close to sea level, will the cave be swamped with sea water? Is it possible to block the water coming in or do I need to raise the land to get the cave area above sea level?

Thanks.

P.S. BTW, I realise I will have to build some sort of "cavebox" to stand on (and look nice) because the solid ground would be above me.

You terraform the land, and place a top on it. In a mountain, you carve out the area, on a flat mainland you may need to raise the land. There are textures to use for the top that almost match the ground texture. You can hide edges by using rocks and landscaping. When you terraform there is no way to keep the land above your head, you must build a top for the cave. If you are close to sea level yes, you'll hit the water. Raise the land up higher first. No need to make a cave floor unless you want it flat and even, and yes you can walk on that ground.

Thanks Shayla, that makes sense and answers everything . I am about to get some land and wanted to know this in advance to help me plan the layout.

An other consideration is to get a piece of land at a sim which welcomes caves - it makes for a much nicer cave if the sim has a mountain theme already. Then your cave can be completely hidden as the whole sim is full of boulders and trees, and you can make some really nice designs which fit in with the neighbors - elven and middle ages sims are often good for caves.

** From what I have seen it is possible to build a cave underneath the ground as the ground is not solid underneath the ground layer that you stand on. Is this correct?

Not quite. While you can place structures below the surface of the terrain, you can't go below the terrain surface normally with your avatar.

**Assumig the answer is yes, how can you "punch" a hole (i.e. cave entrance) through the ground layer so one can get to the cave? Is this possible or does one have to teleport to the cave?

See above. Not possible.

**Finally, if the land you are creating this cave on (underneath the ground) is close to sea level, will the cave be swamped with sea water? Is it possible to block the water coming in or do I need to raise the land to get the cave area above sea level?

Yes, anything below the water level in the sim (20 M elevation in most sims) will be flooded. You can't eliminate that water just in your area. The sim owner could eliminate the water for the whole sim by lowering the water level to zero, if it was a private sim. But then the edges won't match with the void sims around their sim.

Look here for details on how terrain is defined:
https://support.secondlife.com/ics/support/default.asp?deptID=4417

It's best to think of terrain in SL as a rubber sheet. You can stretch it up or down, but can't slide the control points from side to side. The control for terrain height is a grid of 256 by 256 pixels, which forms a 1-meter spacing x/y grid. Each of these pixels can have a value between zero and 255, representing the height in Meters for that point in the terrain surface. A second 256 x 256 pixel channel in the .raw file that defines the terrain is a "height multiplier" layer that can alter the primary heightmap by a multiplier factor that ranges from 1/4 to 2x. So using the multiplier, you could get a vertical resolution of 1/4 Meter, but a max height of only 63 Meters, or a resolution of 2 Meters vertically and a max height of 511 Meters. The multiplier factor can only be used when dealing with imported .raw files, on a whole-sim basis. The in-world terraforming tools can't affect that factor.

What all this means is that all "digging" in SL will form open-topped pits or trenches, with sides that slope outwards towards the edges. Caves require covering the tops of these openings with prims.

The best terrain for making caves has a lot of land above the water surface, and at least one sloping side that you terraform a notch into for the lower cave entrance.

Thanks everyone for your replies. And thanks Ceera for taking the time to put in a detailed explanation on how terrain works in Second Life. I have some experience on using terrain in Unreal Tournament 2004 and UT3, however, they allow holes to "punched" in the ground and water excluded.

With all the replies I believe I have something to work with - thanks.

I like it when caves or other builds are underwater to take advantage of the dark and murk.

Yes, so do I . My land is on an island so I may have to re-think my original idea to fit in with the SL terrain technology. I was planning to have 2 cave entrances with one underwater, one on ground with a tunnel joining them. I may still be able to do that but will require a slightly different approach to what I planning.

I have also often seen caves hidden under lakes, and with entrances done as waterfalls. Water has the advantage that it is "naturally flat", and therefore do not look silly as top, even in an otherwise hilly area.

You can do that - it's not hard.

Just terraform a "canal" for your sea entrance, that leads to the cliff-side notch for the above-ground entrance, and cover the top of that canal with prims as you go...

I did a fairly large (3 floors) underwater building once.

You can't explicitly control the "murkiness" or the blue cast to the light when you're under water. at short distances, it looks fairly normal. But anything much over 20 M in a straight line and there is no doubt the cave isn't filled with air...

Many A/O systems will detect when you're flying or moving under water, and will make you "swim" when you fly below the water plane.

But I have seen it done, and done well, so don't give up!

Another approach... Put a teleporter at the entrances, and do the cave itself in a skybox...

Good idea. That would work but the prims would have to look like natural ground from above and blend in with the rest of the land.

That's ok. I want part of the tunnel to be underwater.

I was thinking about that as an idea as well including having fake doors which fool the person into clicking to open and getting transported instead.

Thanks.

There's also a cave sculpt pack by Cel Edman, it's quite realistic, because you will need prims as well. You really only have to worry about the exact spot people walk through the water table. This can be concealed fairly easily. You can use a set of dark prims, I used a few with a slight transparency to them, stacked through the actual water. So from above it just looked like it was getting darker and darker. Once you are under the water table it just gets dark, even at high noon

...has some nice caves.

Another approach is to have a touch door to enter cave, but it actually teleports you to a skybox that looks like a cave interior.

Well, what about Greenie's? You have to walk through a cave-like passage to get to the place. Maybe wandering there will give more pointers. There's a landmark billboard for it near the Ivory Tower of Prims.