FT3 And Water

nbirkholz · October 2011

FT2 tends to strand a lot of water in interior lakes with no outflow, which is not as common in the real world. Seemingly the water model doesn't outflow from lakes, only inflow. Does FT3 improve this situation?

Secondly, the FT2 seem,s top generate a fair number of straight rivers, is that different in FT3?

Ralf · October 2011

The river algorithm has not changed in FT3 as far as I know, rivers stop when they hit water, no matter how large the body of water is - basically there is no way for FT3 to tell what a lake is or what a sea. Use the Fill Basin function to remove unwanted lakes that stop your rivers short.

Simon Rogers · October 2011

Do Fill Basins before doing Tools >> Actions >> Rivers. Use a very high resolution (say 4096 if your PC can handle it) and the rivers won't be as straight. There will still be some straight sections.

The final thing you can do in CC3 is to fractalize then Straight to Smooth all the rivers.

Ralf · October 2011

And it's normally easy to draw the river outflow from the lakes in CC3 too.

Master TMO · October 2011

Do the rivers before you fill the basins with water. Once your rivers are done, then fill basins with water, and presto! Lakes with river outflow!

nbirkholz · October 2011

Yeah, I played with the order of lakes then rivers or rivers then lakes in FT2, but Rivers before Lakes generates Lakes with multiple outflows, which is similarly unnatural. I can solve either option with CC, but my Cartography minor makes me not want the rivers flowing uphill. Maybe there's a medication I can take instead.

Thanks for the answers.

jslayton · October 2011

The fractal functions in FT have basins at all scales, which turn into lakes when they are below water level. As has been pointed out, filling basins will alleviate this problem somewhat for basins above the base sea level, but this still leaves the little lakes within the continental boundaries themselves. One way to reduce the smaller lake spots is to:

1. Select all land above sea level (Select>>Altitude Range, above 0).
2. Expand the selection a few samples to kill the holes that were the little lakes (Select>>Modify>>Expand with an Amount on the order of 3 to 10, depending on your world and editing resolution).
3. Contract the selection by the same amount to get back roughly the original selction, but now without the lakes. You will also connect up some parts and possibly get some odd connections to the land from islands; these are not a major issue.
4. Lower the water level in the selection so that the lakes appear as dry land (Tools>>Global Lower>>Water Level with a value of 100000 or so)
5. Fill basins (Tools>>Actions>>Fill Basins in Offset).
6. Restore the water level (Tools>>Global Raise>>Water Level with the value used in step 4)

This sequence of operations will usually kill little lakes. Manually painting them out (especially with the prescale painting tool) will always kill them.

I have never seen FT generate more than one outflow from a basin. Do you have an example screenshot?

nbirkholz · October 2011

I attached a representative screenshot. The process is to Find Rivers and then Fill Basins as Lakes. This overlays the rivers with lakes in the basins, which often produces multiple outflows. The version I am using is the free trial of FT2, so version 2.2.

When you export, the rivers are on a separate layer? I could edit that way in CC, right, removing the extra outflows?

jslayton · October 2011

Ah, I see. It's not really multiple outflows, just a mismatch between the display resolution and the river routing resolution (there's no good way to fix this except to use the burn into surface operation, which has its own issues). For your purposes, it's multiple outflows, though.

The straight river segments across the basins and lakes are caused by the basin fill algorithm filling the basins with a slightly-sloping sheet that has no roughness for the rivers to wiggle around.

I think the rivers are on a separate layer, yes.

Master TMO · October 2011

I export rivers separately by just coloring my land and water white.

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FT3 And Water

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