Geofiction Base Maps using Wilbur

[a2area]

Here is what a couple more incised flows did applied at different settings to 3 different elevation groups. I think it gives a better feel for this scale and I am happy with it for the purpose. Most of all what i'm looking for is relative consistency from map to map that will stand up at a wider scale (continental) so it wouldn't be in my best interests to start making the landscapes too unique. And I suppose that is where the "fiction" in geofiction comes in! Unique natural featurs that could plausibly fit into this overall landscape don't necessarily have to be featured on the map in perfect topographical scale as much as i would love that.

Maybe someday Wilbur and Fractal Terrains will have a baby (-:

.... one question i do have that i couldn't find a satisfactory answer to:
I have been outputting gray-scale image from FT to open in wilbur.. works fine... BUT, I would like to have wilbur know where sea level is automatically instead of having to mess with the scale or range which wilbur doesn't remember the next time you open the file. I would simply make my color scheme in FT conform to this... output... input to wilbur and boom.. perfect sea level.
How do i do this? Seems like it should be obvious like (ie) "set sea level : RGB value" or something.
It doesn't make sense to have black as the default sea level when you have negative elevations (depths).

[su_liam]

First point. Images don't contain real elevation data, just numbers fro 0 to 255(0 to 65,536 for 16-bit), so you have to use the Mathematical>Span filter to tell Wilbur what span of heights the image represents. You can find a tutorial here to tell you how to save the data in a full precision binary format. You really want to avoid greyscale image files for elevation as much as possible.

Second point. You are now required to put up a tutorial on exactly how you did this:

Here is what a couple more incised flows did applied at different settings to 3 different elevation groups. I think it gives a better feel for this scale and I am happy with it for the purpose..

I think you might be using something similar to what Mr. Slayton does here, but if you've come up with something that works better for small scale(large area) terrain, then me wantee!

[waldronate]

Maybe someday Wilbur and Fractal Terrains will have a baby (-:

I sure hope not because Wilbur gave birth to FT 0.0 12 years ago...

I would simply make my color scheme in FT conform to this... output... input to wilbur and boom.. perfect sea level.How do i do this?

In FT's File>>Save As menu there is a file type called "Wilbur MDR Files (*.mdr)" that outputs the current view as an MDR file. I recommend this file type for use with Wilbur. I also recommend http://www.ridgenet.net/~jslayton/Th...ain/index.html as a tutorial for using Wilbur together with FT.

[a2area]

I sure hope not because Wilbur gave birth to FT 0.0 12 years ago..

UGH.. well that would be incest then, huh? hah.. then why can't you use wilbur like a sphere and erode the whole dang planet... or can you and i'm just ignorant... which i am since i'm a wilbur newbie.

Thanks for that .mdr advice.. i had no idea. AND that link to 'there and back again.' I have randomly found some of his pages via the wilbur page and google search. If you know of a better index of his tutorials other than what is at http://www.ridgenet.net/~jslayton/wilbur.html i'd love to find it.

Although i am bit confuse about this tutorial here http://www.ridgenet.net/~jslayton/Fu...ol5/index.html I can see he's going from wilbur to photoshop and i think i get the concept but am losing him at the last 2 pics.. he says he's applying more erosion so it has to be in wilbur.. then is he again going back to photoshop and compositing it for us to view? To a newcomer it almost makes it look like it's all being done in wilbur (the 'refilling' of the lakes) but in reality i think most of it is just masking in photoshop using the outline of select basins. Am i right here?

Well, i've got a lot of experimenting to do. Thanks for the help, i'll try to be more resourceful digging up info before asking.


and yes su_liam, i did use that tutorial you linked to.. i did a different setting for each of the low, med and highest terrains.. then went back one more time overall to finish it off nicely. I have i all written down so i will most definitely do a tutorial on how i get my final satisfactory results when i get to that point.

Thanks again.

[waldronate]

The erosion and flow algorithms in Wilbur are all planar algorithms (one of the reasons why they look reasonable only over a limited range of scales). They generate plausible results only for equal-area projections. The typical Equirectangular projection where latitude and longitude are equally spaced isn't this sort of projection and you get odd puckers near the poles when you try to apply such algorithms. In FT, for example, the river routing algorithm looks mighty odd when it's in the polar 10 degrees or so.

The solution for this problem is use an equal-area projection, but then you have the problem of how to wrap at the edges. The most general solution is to provide a connectivity map that specifies how every pixel is connected to every other one. There is no good way to generate this connectivity map except with knowledge of the map projections.

There is a projection that I learned from Dave Allen that is very roughly equal-area and has simple connectivity rules: start with a square map and declare the upper-right corner to be the north pole, the lower-left corner to be the south pole, and the diagonal from upper-left to lower-right to be the equator. Connectivity is then simple (when you go off the top you come back in on the right; going off the bottom you come back in on the left) and quick to compute with no connectivity map required. I need to implement this algorithm in the various flow computations in Wilbur one of these years so that folks can do whole-world erosion and river computation.

The last 3 pictures in the Fun With Wilbur Vol. 5 tutorial have all been composited in Photoshop. I probably should have made that clearer in the tutorial.

The index on the Wilbur page has all of the available tutorials Wilbur tutorials. Please always feel free to ask if something is unclear. It's how we all learn, especially when there are too many features and not enough documentation. Many times user questions have led to useful features and explanatory documentation. Wilbur is a manifestation of my unwillingness to finish anything and inability to focus on one thing for too long so it may be difficult to actually use.

[a2area]

There is a projection that I learned from Dave Allen that is very roughly equal-area and has simple connectivity rules: start with a square map and declare the upper-right corner to be the north pole, the lower-left corner to be the south pole, and the diagonal from upper-left to lower-right to be the equator. Connectivity is then simple (when you go off the top you come back in on the right; going off the bottom you come back in on the left) and quick to compute with no connectivity map required. I need to implement this algorithm in the various flow computations in Wilbur one of these years so that folks can do whole-world erosion and river computation.

Sounds interesting.. would make a bizarre looking map in rectangular form but i see the logic in the approach for the purpose of avoiding excess data overlap. I saw a wrapping approach for Jhendor but i believe it was done from two equidistant polar projections. I don't think my computer could handle whole world erosion yet anyhow at a good resolutin (0:

The last 3 pictures in the Fun With Wilbur Vol. 5 tutorial have all been composited in Photoshop. I probably should have made that clearer in the tutorial.

Good, i thought that was the case but then i wasn't quite sure.

I'm loving Wilbur and am cool with the limitations and realize that, like fractal terrains, it's got a lot of hidden (and apparent) power. I have been using fractal terrains passively for a few years but just recently am starting to get to know it better. I can see that together they make sense once you get the feel for the processes. Thank you for the help and i'm sure there will be more questions along the way!

Experiment time...

[su_liam]

Connectivity is fairly straight forward in cylindrical equal-area projections the Lambert cylindrical equal-area projection is the general case. Gall orthographic, Hobo-Dyer and Behrmann are merely special cases.

A good place to look for technical information(formulae and the like) is here at Wolfram Mathworld.

[waldronate]

The problem with all cylindrical projections from a raster processing perspective is that they make at least two points on the globe a line in the raster. That is, there is a non-unique mapping between points in the world and points in the raster. A projection like the sinusoidal projection eliminates the non-unique mapping problem, but the connectivity on the raster gets screwy.

Dave Allen's approximation isn't a conformal or equal-area projection, but it's not terrible (its trivial edge connectivity and pseudo equal-area pixels makes it excellent for raster computations). It also has the advantage that the cardinal direcitons on the work map don't correspond to cardinal directions of a typical projection.

There are many possible solutions for compromise between rigor and ease of use. Dave Allen's solution is simple in the sense that it's only linear math, is a unique mapping, and its connectivity can be implemented with a couple of if statements. I haven't seen a better one yet and I've been looking for one for years. Having said that, I've known about this for 10+ years but haven't gotten around to implementing it anywhere. Sheer laziness on my part.

[su_liam]

The "pointy poles" argument? I gotta give you that one! Even if the projection isn't very attractive, it would probably be better as an underlying projection for the editing tools in FT than the current equirectangular one. Wow, that was a sentence...

I really need to look David Allen up.

[a2area]

it's coming along (0: