The Terrain FX operator can be used to apply various effects to a terrain grid.
Grid names: terrain grids with matching names will be affected by the specified filter.
Mode: the fx mode to apply to applicable terrain grids.
Use interpolator as input mask: when enabled, interpolators applied to a terrain grid (in the interpolation rollout) will mask input, which can have an impact on the overall shapes generated by each effect.
Generate mask: when enabled, changes made to affected terrain grids by a given effect will be mapped to a mask stored in the specified channel using the specified operation.
Operation: controls how new mask values will be merged with existing values, if the mask color channel is not empty.
Color channel: the color channel in which to save the generated mask.
The Terrain FX operator applies effects to affected terrain grids in a resolution-independent manner by using a multi-grid approach. Affected terrains are downsampled and then progressively re-sampled with an application of the effect at each sampling step, up to the starting resolution. This approach allows users to change grid resolution without drastically affecting the result.
The multi-grid curve allows users to control the amount of effect to apply at each sampling step (from lowest resolution to highest). Increasing the effect amount on lower resolutions has a larger impact on overall effect shapes, whereas increasing the effect amount on higher resolutions has a larger impact on overall effect details.
Each Terrain FX effect has a variety of parameters to control its output. These parameters don’t necessarily correspond to real-world concepts, but instead to key aspects of each effect’s internal algorithm. For this reason, an exhaustive/coherent explanation of each one is not really possible because each given parameter is somewhat of a “magic” number that is part of an opaque formula. Users are encouraged to experiment with values to achieve interesting results. Presets have also been added for each effect, to provide users with an idea of the type of result each individual effect is capable of producing when its parameters are tweaked in various ways. The effects and presets have been given real-world names (ex: “dust”, “chunky”, “porous”, etc), but these names simply correspond to a visual interpretation of the types of effects that each algorithm is capable of producing, rather than some scientifically-accurate formula relating directly to those concepts.