Limits on digging

Can anyone tell me what are the rules on terraforming downwards? Recently I tried to dig a deep hole on an inland plot. I could get it down to 20m elevation (starting from about 30 or 35m) at which point I reached the water table, but I couldn't go any deeper. If I had a wider hole, would it be possible to dig deeper?

The limits for terraforming are set at the sim level, and are based on a +/- range from the last saved version of the terrain grid for that sim. So, for example, a mainland sim with a typical +/- 4 M limit and ground level at 24 M in your parcel, would just alllow you to dig down to the 20M 'water table'. If the limits for the sim were +/- 100 M, as it is on most private island sims, you could dig from that 24M surface to at least zero Meters. I can't recall if you are allowed to go to negative values or not. I don't believe you can.

The dimensions of your hole (or hill) do not affect how deep you can dig, nor how high you can raise the land.

The terrain grid is based on points that are exactly 0.5 M apart horizontally, and anything you do to the Z-axis elevation streaches the terrain surface vertically. If you select a 4M x 4M patch of land (the smallest you can select) and depress it to the limits of the sim's terraforming, the sides will slope from the next point 0.5M outside that square down into your hole. If you dig a really deep hole, that draw-down around the edges may get even wider. I once dug from the top of a 60M mountain down to the water table, and I believe the sides of the pit sloped out almost 4M.

Yes, this means that if you terraform right at the edge of your parcel, you CAN affect the terrain in the adjoining parcel, so be careful! It also means that if you dig a basement the size of your building foundation, you'll have a moat around the house - a ditch you'll have to cover with a prim planting area pr patios or other structures. Or you'll need to make the basement smaller than the house foundation.

Extreme changes in the terrain grid from point to point sometimes cause unexpected spikes and crevices, and not necessarily where you're terraforming! These just have to be adjusted whenhj they happen. It takes practice.

(Still remembers her attempt, in vain, to get the Lindens to disclose exactly what is done to the land when you perform a terraforming operation. Their lips were sealed )

Thanks, Ceera, that's very helpful.

Just to add, for the benefit of others reading this thread, that when you buy land it will almost certainly have already been terraformed to some degree by the previous owner. This means that you might not be able to raise or lower it to the degree you thought you would be able to before buying it. More of an issue on the Mainland, of course

You can also get a scripted device free from Yardie Yard (script) that helps with land formation. Put it in a flat prim, size the prim, and move it up or down to shape land, and imho it works better (in some cases) than the standard Linden tools

I agree it works well, but it should be said it is handcuffed by the same restrictions discussed earlier in this thread. There's also a danger of buying the tool underground, requiring a wire-frame edit/selection to fetch and get rid of it once that happens.

No kidding! I was digging my first basement - more like an underwater grotto (fairly deep). When I came back up, the far end of my lot was now awash. Spent a while adjusting that, and went back down to the basement. Now some stuff was buried. After I dug it out and refilled the holes, I came back up and the only thing showing on most of my outdoor stuff was the very top... Should have looked into the wireframe edit Amras mentioned. I'm getting a huge amount of experience terraforming on this lot!

Did that change very recently (1-2 weeks ago)?

There was a little tip sticking out of the water on one end of my parcel (just 5cm across the border), but no matter what I did to my own land, the other side didn't budge at all. In the past you had a little bit of flexibility with your borders (for good or bad I guess) but that doesn't seem to be the case anymore?

The problem is that while you can do something on your side of the parcel border that can affect land on the other side of that border, you can not use the terraforming tools directly on the terrain beyond your parcel edge. So digging a hole near the edge of your parcel could draw down some of your neighbor's terrain, and severe changes could cause those wierd spikes across the border. But you can't 'flatten' their side back out by using the tool beyond the line.

As far as I have been able to tell, things like those spikes are an unexpected glitch, and not something that can reliably be planned for. I had to deal with those spikes a lot when setting up a swimming pool a while back. Dug the hole, and had spikes in the surrounding patio. Smoothed the spikes below the patio, and now had soil edging into the corners of the bottom of the pool. But making changes in the hole didn't repeatably cause the same spikes, nor did changes in the hole ever draw a spike back down.