Falappa.Net

The purpose of this plugin is to add “fractal” irregularities to the existing terrain, that is irregularities present at decreasing scale from the whole terrain to a single feature. This plugin is also well suited for direct terrain creation. For an introduction to the principles of fractal noise and for a deeper insigth on some of the parameters I suggest looking at Hugo Helias’ pages on the subject.

Parameters Description

General Parameters: the scale values are the dimensions of the sampled region in “noise space”, you can zoom in or out the noise by changing this region, unequal values stretch the noise in either direction. The combo box below the scale values allow to specify if the generated noise values replace or sum up to the existing ones.

Noise Type: you can choose from six variations of fractal noise and each one can be fine tuned adjusting it’s parameters:

• The Smoothnoise type is similar to POV-Ray bozo pattern and adds a smoothed noise to the terrain. At certain scales a grid pattern is noticeable, this is not a bug but is instrinsic of this kind of noise (also called gradient noise).
• The Turbulence type is similar to the POV-Ray agate pattern and produces images similar to brain-convolutions with low octaves values or to certain rocks with high octaves values. It adds to the terrain very fractured mounds.
• The Fbm (for fractional brownian motion) type is similar to the POV-Ray granite pattern and produces a good approximation of a standard terrain. It’s constructed adding together several layers (as specified with the octaves value) of smoothed noise, each one has the frequency of the previous multiplied by the lacunarity value and the amplitude of the previous multiplied by the persistence value.
• The Hetero multifractal is similar to the previous type and is constructed in the same way but during the layers summation there’s a smoothing that vary with height, its “height sensitivity” may be tuned with the offset value.
• The Hybryd multifractal is a mix of the former two, the height influence on the noise may be adjusted with the ridges size parameter.
• The Ridged multifractal presents interesting lightning shaped features and produces very good approximations of high mountains. The ridges size parameter sets the ridges emphasis while the height offset parameters balances the proportion between ridges areas and “hill” areas.

Noise Amplitude: the edit field sets the amplitude value while the nearby combo box allows to set how this value is interpreted: in an absolute way that is the value represents the actual amplitude in grid units or in a relative fashion where the value represents a percentage of the existing terrain height.

Noise Seed and Origin: the seed is equivalent to that of the Noise Adder plugin, the origin x and y values are the coordinates of the point corresponding the upper left corner of the terrain in “noise space”; to variate the noise patterns change the seed and/or the origin by pressing the two corresponding buttons.

Noise Displacement: the displacement amount modulates the action of a second noise generator on the look-up of the first.

Noise Parameters:

• The persistence parameter adjusts the roughness of the terrain, the higher the rougher (it’s similar to the POV-Ray omega setting and is sometimes also called H or amplitude multiplier).
• The lacunarity parameter adjusts the sizes of the features (it’s similar to the POV-Ray lambda setting and is sometimes also called frequency multiplier).
• The octaves parameter adjusts the amount of fractal detail ,that is the iterations of the algorithm, (it’s similar to the POV-Ray octaves setting).
• The offset parameter shift the heights for those types affected by height variations (hetero, hybrid and ridged).
• The Ridges size modulates the effect of height changes on the pattern emphasizing or reducing the variations.

Known Bugs

The spinners get out of sync if you enter the values directly in the fields. The spinners resync with their respectives values after pressing the preview or ok buttons.

Tips

This plugins is the far more complex of the collection but it’s in my humble opinion the one which produces the most interesting results. It can be used to add details to an existing terrain or to create one from scratch. I encourage you to experiment with the parameters to test the result of different parameters combinations.

Depending on the noise type some parameters have a great effect for small variations or produce interesting results in a different range of values, so when you change the type you have to retune the values.

Applying a noise displacement slows the plugin down cause it has to perform two noise lookups per location.

A common characteristic of all the noise types is that they have an adjustable scale and a number of octaves: those paremeters depends on the size of the current terrain, smaller scales value or higher detail level values have a noticeable effect only if the heightfield is big enough.

The multifractal types have two paramters more than the others: offset and ridges size. The first parameter tunes the influence of height on the generation algorithms, those types infact are studied to generate smoothed rollhills at low heights and rougher mountain peaks at high points. The ridges size parameter sets the strength of secondary features over the main ones: choosing a high value makes the sides of main mountains full of noticeable wrinkles.

A good starting set of those parameters for the Ridged multifractal type is:

• Height Offset: 0.6
• Ridges Size: 2.0

For hetero and hybrid multifractal types the offset value should be lower than the ridged one, namely around 0.2 - 0.4, while the ridges size value should be a little higher, say 2.1 - 2.4.

Examples

	A Hybrid multifractal with: Lacunarity: 2.1 Persistence: 0.25 Octaves: 7.1 Offset: 0.15 Ridges Size: 3
	A Ridged multifractal 50 grid units tall with: Lacunarity: 1.9 Persistence: 0.85 Octaves: 7 Offset: 0.4 Ridges Size: 2.5
	A Hetero multifractal with: Lacunarity: 2.02 Persistence: 0.25 Octaves: 5.5 Offset: 0.1
	First Turbulence with the following parameters: Lacunarity: 1.7 Persistence: 0.1 Octaves: 4.5 Then invert the result and add a Fbm at 15% amplitude with: Lacunarity: 2.0 Persistence: 0.5 Octaves: 7
	This rusty surface has been obtained subtracting from a new terrain a Fbm with: Lacunarity: 2.1 Persistence: 0.9 Octaves: 8
	This very “natural looking” scape has been obtained from a displaced Fbm with: Scale X and Y:2 Amplitude: 20 grid units Displacement amount:0.3 Lacunarity: 2.1 Persistence: 0.55 Octaves: 5.5