Long Rivers and DEMs

[Milaga]

I've been looking through some of fishlipsatwork DEMs, spending a significant time on the Mohawk-Albany-Binghamton <kuid2:59012:103143:1> mega-line.

The DEM has around 70 miles of the Mohawk river. While trying to see how to lay prototypical track around this river I noticed that the river is a great calibrating tool to match the DEM data and Tiger lines.

By filling the riverbeds with water I can see how close the Tiger lines indicating the river shore are close to the actual DEM data. This gives a good indication about how far off the track Tiger lines are for the initial placement of track.

I noticed that for the most part the riverbed is perfectly flat. Moving up river the height of the riverbed periodically increases sharply. I assume this is where two DEM datasets were merged and that each had a different height (probably averaged across the dataset). The riverbanks at these points blend seamlessly, but the river itself has a somewhat steep drop.

I cannot see a way to model the river using this DEM data. The land around the Mohawk river slopes gradually downwards across it's length. Over 60 miles this creates quite a height difference. If I use the water level at it's western most point the river would flood the entire tri-city area. If I use it at it's eastern point I would need to create deep chasms in the west for the water to flow in, which doesn't look right at all.

To those of you who are using DEM data with rivers, how do you handle the differing heights of the river?

 

[MrScott2006]

The only way to do this is to use a waterfalls or a dams. In the Susquehanna layout that followed the Susquehanna River about 60 miles, I had to use 3 dams.

 

[mjolnir]

Not too long ago, I'd have agreed with MrScott2006, but I think this another application for my "structure as landscape" idea would work. Use a content creation tool to create a structure which has the same profile as the river banks and river for the desired length, create a texture which comes as close as possible to the texture of the bottom of the river bank, and apply it to the river, and then install the texture. The "structure-as-water", unlike the built in Auran water, can have a different height at on end than the other. I expect that it will take a fair amount of fiddley work to get it exactly right, but I also expect that if you use this technique beneath a bridge, that the amount of fiddley work would be minimized.

ns

 

[gfisher]

The problem with all the splines I have seen to date is twofold: The dirt or grass edge of the spline doesn't blend very well with Trainz's ground textures and the creator usually uses some inappropriate color like bright blue to represent the water. The texture problem is hard to solve because even if you start with the same texture, differences between the way a gmax texture appears and a ground texture is rendered make a match difficult to achieve. I'm not saying it can't be done, but having tried it myself I know it is not all that easy.

It occurs to me though that if you were to create a wide spline made up of two surfaces, a river bottom in a dark muddy color for example, and above that another surface to represent the water which could be bump mapped to show ripples and alpha channeled for transparency, say 7 meters apart, you could then dig the river channel and lay the river spline into it, and of course it would be height adjustable. The banks would vary with the terrain and would be textured as you choose and would look fairly natural, or at least as good as Trainz water now. Could you animate the bump mapping? I assume you could, although I have no idea how this all might work with a splined surface.

I would try it, but I know nothing at this point about bump mapping. Maybe one of you Blender guys could try it.

 

[mjolnir]

While it's true that Blender supports bump mapping, I suspect that the TRS XML importer does not, at this point. My preliminary attempts to export any material or texture from blender other than a graphics image have been unsuccessful.

 

[clam1952]

I just carve out the river bed to a width narrower than the spline I am using, lay the spline then lower it so the edges are under the bank, there are some river splines that don't look that bad if you are not going to dive into them so to speak, and you can always tweak the colour or texture if it's not going to be uploaded. Works better with the 5m squares in 2009.

 

[backyard]

Rivers are never flat...

All rivers start at a point higher than the location where it disappears into a larger body of water. If not, it would be a "long lake!"

It is perfectly acceptable to step-down the height of the water using a rocky texture or actual dam structure.

You can install a section of river at one height, stop at a location & start laying water at a different height just beyond the end point, then lay individual squares back to the end of the last.

If you raise the height of the lower section to that of the previous, it will join together & you have to start over.

Raise the terrain height to cover the separated levels, texture & go on Further.

Using Microsoft Virtual Earth(now called Bing), you can find the actual terrain elevation at any point.

 

[Dermmy]

I go with the waterfall/dam approach. Sometimes it works better than others depending on the locale. Definitely better than any 'river' splines I have tried, but then I haven't tried them all...

Andy

 

[gfisher]

Here's a quick cut at a height and slope adjustable creek or small river spline made from a rippled water texture and a uniformly shaded alpha channel.

My idea of including a river bottom didn't work because Trainz seems to get confused about how to render the bottom spline... is it hidden or isn't it, but that doesn't really matter since you would normally just texture the bottom any way. It would be even better with bump mapping, although not animated of course.

Why didn't I ever think of this before.

 

[Dermmy]

Nice one George

 

[bl4882]

That is awfully good for a quick cut, and seems incredibly useful, too. A little dressing around the banks and it could look first rate. Would you consider putting it on the DLS for those of us who are Gmax/Blender challenged, please?

Bernie

 

[gfisher]

Yes I intend to do that, but first I have to go back to the water texture and refine it a bit further so it tiles properly. I also tried out a small river rapids spline, shown here.

 

[Jerker]

G'day gfisher,

That's a brilliant 'solution' to the problem. However, I am wondering, given the initial 'issue' of this thread, if you could 'find' a water texture of calmer waters that matches the 'rapids' texture that could be used alternatively to the rapids 'spline' so that the rapids could be placed only in those locations where the river changes elevation, whilst the rest of it remains 'calm'...

...more like the real thing (there aren't too may rivers that are rapids along their entire length)...

Jerker {}

 

[clam1952]

Yes I intend to do that, but first I have to go back to the water texture and refine it a bit further so it tiles properly. I also tried out a small river rapids spline, shown here.

If you release that rapids one I will be eternally indebted to you as that is actually just what I am looking for, I've been trying for ages to get exactly that sort of effect for a small pass on a Welsh Narrow Gauge route I've been working on for the last 11 months.

 

[northcornice]

The rapids are fantastic, a little glacier silt aquamarine colour would be perfect for a mountain river!

 

[backyard]

...my flav of the month...

Dunkles Wasser Grund Sand 3 Kuid:68787:21028 makes a good water in some areas...it's a little green & requires no working with the directional keys.

 

[Milaga]

That looks fantastic, gfisher. If you put that on the DLS I will definitely use it on the creeks leading into the Mohawk river.

Water heights only need to be separated by a single square of non-water to keep them from blending together. With creative manipulation of a river bottom I could see these rapids used to disguise elevation changes around bridges.

I'm I ever glad I asked this question. Now I can start worrying about how I'm going to place the Erie Canal.

 

[backyard]

...Room For Squares....

What I'm saying is if you turn around & place the squares from the opposite direction, you can run up to the split...it may take one or two times but it will not merge once you establish the different levels....unless you change either level without thinking.

Creating these elevation changes in an obscured location if possible will help you decided how to treat the site as appropriate.

Changes of less than one meter can be done without problems, but it takes practice.

It's mind boggling how much elevation change a river goes through in sometimes a very short distance. In fact the same gravity that pulls the water downhill also causes it to lay flat against the ground otherwise it would empty the valley pretty quick.

I suspect something as crafted as the Erie Canal may take all the tricks you can muster.

 

[higgikay]

Great work gfisher. This will be for sure a perfect addition to the water spline set "Cyberstorm" has created. You can find it under his name on the DLS.

Cheers Kay:wave:

 

[ldowns]

If you post these I for one will be eternally grateful, as rivers/streams are one of the biggest frustrations in Trainz...

Thanks,
Lamont