Explanation of Wilbur's add, subtract, multiply, divide, etc.?

[Pananacakes]

When you make some land form or adjustment with Wilbur you often have an option about how to apply effects: Replace, Add, Subtract, Multiply, Divide, Min, and Max. When I try things out, changing these options, I don't usually get what I expected. Like when adding fractal noise I expect the new noise to be applied on top of the existing land, so the heights from the new noise rise up from the pre-existing landscape. But it doesn't seem to work that way.

What do these options really mean and how do they apply effects?

[waldronate]

The operations in Wilbur are defined as:

result = surface op value

Where surface is the current surface value, op is the operation to perform (add, subtract, etc.), and value is the numeric output of the activity being performed (e.g. Surface>>Fill>>Constant will use the number provided, fractal noise will generate a number at the given point from the fractal field, and so on). The operations min and max return the largest and smallest values of (surface, value), respectively.

For example, the Add operation with fractal noise might work like this:

A given point on the surface currently has a value of 50 and the generated fractal noise has a value of 12. The result of the Add operation would be 62=(50+12), Subtract would yield 38=(50-12), min would yield 12, and max would yield 50.

One thing that might happen with add is that if you are adding a value that's substantially larger than the existing terrain, you might only see that value. This can happen easily with the fractal noises because the default range is only -1 to +1 and successive operations will have that same magnitude.

Note that after the computation is performed, "result" is blended into the surface through the selection. This final blending step prevents the result from affecting the surface in unselected areas.

[Pananacakes]

Thanks Waldronate.

[Pananacakes]

Which settings increase the range of the noise? Also is there any way to tell what the precise height of the pixel under the mouse cursor is?

[waldronate]

The precise setting to control noise amplitude will depend on the activity being performed (unfortunately). On Filter>>Noise>>Fractal Noise, it's "Amplitude". On Filter>>Noise>>Absolute Magnitude Noise, it's "Noise magnitude". And so on.

The right-hand part of the program status bar (bottom of the window) shows the mouse position to the left of the colon and the surface value to the right of the colon.

[Pananacakes]

It just occured to me that Wilbur ought to have its own sub-forum.