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View Full Version : How do I simulate past Ice Ages/glaciation?



Master TMO
06-19-2011, 07:21 PM
I'm a bit hazy on the actual science of what happens to the ground under an Ice Age. I'm looking at trying to quantify the effects and adding them to my world-building script.

Here's a few of the things I think I've read about, and how it might be simulated in FTPro:

Land is pressed down / (elevation is lowered)
Hills are ground down / (roughness is lowered)
Mountains are eroded / (Incise Flow is applied?)
Dirt & rock is deposited at the edge of the glaciation / (??)


I think I might be able to simulate the extent of the glaciation by tweaking the Albedo/Light/Greenhouse settings, although I'm not sure what valid settings might be. I've played around a little bit, but if anyone can point me to any resources or information to educate my playing around, I would appreciate it.

Also, if you have any suggestions for methods and settings for the ground effects list above, they would be most welcome.

Master TMO
06-19-2011, 07:46 PM
Interesting... I was playing with trying to simulate glaciation and lowered the Greenhouse setting a bit, just to see what happened, and polar ice caps started appearing. Does anyone know the rules for ocean to start turning into ice in FTPro? Changing the greenhouse to make polar ice caps appear practically froze the rest of the planet, so I'll need to fine-tune it some, but it's an interesting start.

Ascension
06-19-2011, 08:16 PM
No idea how to do what you're doing since I don't have the software but I do have one tiny thing to add - moraine. That's the pile of rubble at the end of a glacier. In terms of visualizing it, though, I wouldn't bother; it's just some stray rocks of varying size from pebbles to boulders and has no real affect on the terrain. It might be more fertile but that, too, is also not really worth trying to visualize since, if the glacier retreats, the land is still mostly tundra with thin tough grasses and sparse small shrubby trees or, at best, taiga with coniferous forests.

Master TMO
06-19-2011, 10:05 PM
Moraine is what the 5th list item is referring to; I just couldn't remember the appropriate term. FT has a climate called tundra - is tundra pretty much only created by prior glaciation? If so, then just selecting that climate region would be a reasonable shortcut perhaps to tweaking all the climate variables.

Ascension
06-19-2011, 11:59 PM
No tundra is more of a climate thing than glaciation thing. But I guess that if you had a really colossal glacier it might generate its own climate.

waldronate
06-20-2011, 11:30 PM
In FT's gaia shader, ice caps form at +/- 76.5 latitude plus an fBm noise factor. No, you can't change it.

In FT's climate shader, ice caps form at an annual average temperature of -10C. No, you can't change it. Other climate types appear according to an internal lookup table ( http://www.ridgenet.net/~jslayton/climateinfo.gif ). The image climate shader lets you put an arbitrary picture over that climate image to determine the coloring.

I am more likely to play with the "Specify Base Temperature" options in FT to control the worldwide temperature than I am to try to use the "Physically-based Base Temperature" options.

Master TMO
06-21-2011, 02:08 PM
Hmm... okay. If I understand the temperature mechanism correctly, changing the Base Temp would equally and evenly change the temps across the globe. So if it's set at the default of 59.5, and I changed that to 54.5, the temp would drop uniformly around the map by 5 degrees.

Which means it fakable using scripts by selecting temps 5 degrees higher than the ostensible target.

Of course, the chance that I understand the temperature mechanism is at best 50/50. ;)

Right now I'm looking at selecting everything 48 degrees or less and below 7500 ft elevation, then lowering the roughness by .1 and elevation by 500 ft. No idea how realistic that will be yet. I still have to play with it.

gilgamec
06-22-2011, 01:15 PM
I'm a bit hazy on the actual science of what happens to the ground under an Ice Age. I'm looking at trying to quantify the effects and adding them to my world-building script.
...

One telltale sign of glaciated terrain that you haven't mentioned is the specific shape of glacial valleys; they start with big bowl-shaped areas called cirques near the top of the valley (which often fill in with lakes after the glacier retreats), then this U shape continues down the valley; this gives you smoothly sloped bottoms near the middle of the valley, with steep slopes up to the surrounding hills. I'm not certain that an incise-flow tool would give you that sort of shape, but I'm not familiar enough with FT to know if there's a tool for doing what you'd need.

Master TMO
06-22-2011, 05:38 PM
Very interesting. I doubt I could get incise flow to do the cirques, but the rounded valley might be possible. I'm no expert on incise flow either and will have to play. Good info, thanks!

Master TMO
07-01-2011, 06:18 PM
Okay, here's an image created with Incise Flow and Fill Basins with Water. Can you folks critique it for me? Good, bad, so-so?

36800

Update: Not sure if that's a good enough view of the area. I'll add a larger range view in a bit.

Master TMO
07-01-2011, 09:03 PM
Well... drat. Incise flow doesn't stop at selection boundaries. This is going to be trickier than I was hoping. Gotta find a way of running and not running incise flow at the same time?

waldronate
07-02-2011, 03:19 PM
Well... drat. Incise flow doesn't stop at selection boundaries. This is going to be trickier than I was hoping. Gotta find a way of running and not running incise flow at the same time?

I can't reproduce this behavior. Incise flow operates at the editing resolution, which might be a cause for little apparent effect.

Master TMO
07-02-2011, 03:29 PM
Hrmph, I think you're right. I just ran a drastic test case, and it *did* stop at the selection boundary. So I guess I was just mis-interpreting what I saw. It's entirely possible, it's been a very stressful week, and my brain isn't running at peak performance right now. But thank you for checking into it for me!