Some fractal terrain questions

[waldronate]

Basin Fill fills basins, regardless of depth. The parameter that you enter controls the slope at which the basins are filled (-1 means that Wilbur computes an appropriate slope for the image resolution). The edge of a basin is either sea level or the area that would be full of goo if the world is flooded by a viscous goo (the parameter you enter on basin fill is approximately equal to the viscosity of the good - a value of 0 means that you'll get flat-filled basins; a value of -1 means that you'll get slightly-sloping fills on the basins that allow for rivers to be correctly routed across the basin). Fun with Wilbur, Volume 5 shows how flow across basins filled with -1 look.

The way that you keep basins from getting filled is to make them not basins. Cut a small channel at the edge of the basin to let the water out.

[Naima]

I am trying to use the brush to cut in but despite I tried all values between -1 and 0.0001 it alwys carves the same depth .
I am missing something there ? I can't get those brush to work seamlessy ...

also tried the fractal add on to add more noise , I noticed there are scale functions but also there regardless of the several tests I didn't get any appreciable result and the info on the manual didn't help me understand how t apply the fractal ...
for example in place of adding generic noise of 10 % I wanted to add more bigger clusters of fractal terrain , but didn't work .

[waldronate]

Using the paintbrush, the value you paint in Wilbur is the altitude you get. If the lowest depth of your basin is 100, setting your brush to 100 and operation to Lerp (linear interpolate) will put the value 100 under the brush wherever you paint.

The default range of values for the ridged multifractal noise function is 0 to 1 with a very approximately Gaussian distribution (I base this on starting a new surface, doing Filter>>Noise>>Fractal Noise, accepting the default settings, and then using Window>>Histogram to look at the distribution - kind of a 2-hump thingy, but very approximately Gaussian). On the Fractal Noise dialog, "Amplitude" is the amount to scale the result by. Entering 1000 for Amplitude and setting Operation to Add will get fractal noise values from 0 to 1000 added to the existing altitudes in your selection.

[Naima]

but the size of those "fractal bumps" are regulated by what? Sorry I cna't understand the specific entries in that window, like the intensity , size, tiling , dimensions add, remove etc ... Is there a precise description of what it does with the results = I woudl like ot use that to Break the River flowing straight, but I mean the LArge Amazon rio like rivers , not the smaller ones, those I can break eventually with the normal % noise .

about the brush if i want to paint and link for example two river basins, one upper map and the one down map , but in middle there is a small hil and I want to make the river pass throught that so I used the brush , but that cutted the hill in two , and then going down it rised a ramp to the other river , that is more down in valley compared to the upper one , so to link better them by hand how should I procede in wilbur?

thanks for ur huge patience with my questioning btw ...

[waldronate]

On the Fractal Noise dialog, there are two columns of values: The left column (H, Lacunarity, Octaves, Offset, fgain) are the fractal parameters. The only thing you'll normally need to change is the number of octaves. This being Wilbur, try to keep that value below 12. The right-hand column is a little more useful. Amplitude describes how much the fractal should be scaled. XY Scale describes how large of a plane to evaluate. The default value of 2,2 gives features of a specific size. Increasing this value will give more closely-packed apparent features (4,4 will show an area twice as large in X and Y as 2,2 for example). XY Origin describes where to start evaluating the noise on the surface. If you change these value a little, you are effectively panning though the surface. The final parmeter on the right, Displacement, is where on the Z axis the XY plane is evaluated. Changing this value repeatedly by just a little (say 0.1) without changing anything else will effectively provide a set of maps that "evolve" over time. As an aside, Window>>Journey Through Texture Space provides a way to create a set of maps that differ by an amount specified. At one point, the slider worked, but it seems that I broke it along the way again.

You can use the brush tool in Wilbur to raise or lower instead of setting the value to a specific height. The tools below the paintbrush on the tools palette are lower and raise, respectively. Using a value of 0.01 (entered on the paintbrush toolbar accessed via View>>Toolbars and Docking Windows>>Paintbrush Options) and a largish brush size. These tools may seem similar to the ones in Fractal Terrains. Both programs use pretty much the same code for these features (Wilbur had them first, if I recall correctly).

Finding a user willing to ask questions is very helpful. Feel free to ask more. If some of my answers seem a little short, it's likely because I have distractions in the immediate vicinity.

[Naima]

Previews doesnt work either, and woudl be usefull ... I am trying to understand that fractal nose but I applied leaving all as normal on a selection height from -500 to 5000 m with all default apart octaves set to 8 and xysclae to 1 , as if I understood increasing it woudl show more packed noise ?

I didn't understand then what means the origin thing anyway .

as for slider I do not see any and no z option ...

I have latest wilbur version

but I can't see good results here ...

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[waldronate]

The slider was on the "Journey Through Texture Space" window.

To help with the noise visualization, imagine a large parking lot (or other fairly large paved surface). The texture on the surface of the parking lot (be it gravel, cobbles, macadam, or other such) represents your noise function. Now imagine that you're going to take a picture of the surface. If you take a picture of a 10cmx10cm area, the texture of the parking lot will be pretty prominent. If you take a picture of a 1mx1m area, the texture will be less prominent, an so on. The size of the area that you photograph is equivalent to the XY Scale part on the fractal noise dialog (thus, as the scale gets bigger, the features get smaller). Where on the parking lot that you take your picture is equivalent to the XY Origin. The analogy breaks down when the notion of Displacement is introduced: it would be equivalent to a 4D parking lot that gets rotated in; we'll stop there. The implementation in Wilbur is simpler: all noises in Wilbur are defined as 3D blocks of values; it is similar to a cloud with its varying intensities. What Wilbur does is to extract a single plane in X and Y at a given Z value (the Displacement value) and use the intensity at each point as a height value.

If I understand correctly, you're interested in adding noise to the low-lying areas of the world. For some reason, the "Fractal Noise" tool isn't adding the results in correctly. Time to fall back on an older tool: Filter>>Calculate Height Field. This tool is the general computation dashboard of which the Fractal Noise, Spherical Fractal Noise, and Calculate Function tools are special cases. On the Height Field Computation dialog, turn off the "Spherical Evaluation" checkbox unless you want full-world spherically-corrected noise to be added. Set Operation to Add. Set Position to the XYZ origin that you want and Size to the XY scale that you want (Z scale doesn't do anything; you can ignore it). Click the Scaling button to bring up the Surface Scaling dialog, select Single Value, enter how much noise you want added and then click OK to dismiss the Surface Scaling dialog. Click OK to dismiss the Height Field Computation dialog and add the noise to your surface. For best results, be sure to feather any selection to avoid hard edges on the values.
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[Naima]

Is it possible that there might be memory leaks on Wilbur ? I have 32 gb ram , I have launched a erosion flow on a 16384 x 8192 map and it popped up a message to close other programs couse memory was missing .

[waldronate]

It is quite possible that there are memory leaks in Wilbur.

Each pixel on the map takes up 9 bytes of memory (4 bytes for height, 4 bytes for color, and 1 bytes for selection) and each pixel in each undo level takes up 8 bytes of memory (4 bytes of height and 4 bytes of color). You're looking at about 1GB per operation, not counting any temporaries (the basin fill uses several and from different memory pools) or overhead in the system. The default is 8 undo levels, so you can easily be running up against the limits of your system after several operations.

Try using Edit>>Preferences to set the number of undo levels down to 2 and see if that makes any difference in memory usage.

[Naima]

Ok thanks , btw I doscovered why earlier some of my mdr opening were not working .
I can't open them when I have both instances of Wilbur and Fractal terrain contemporarly trying to open the same file or one have it loaded already .

I have mixed in the workflow also world machine ^^ ... but I guess I can't ask you things on that tool also hehe .... I am trying to find a way to not erode under the sea level though wich is not actually one big problem to overcome ...