Masks

A mask is a greyscale map from 0 (black) to 1 (white). Masks describe where: where the ground is steep, where water collects, where trees grow. They drive colour, vegetation, blending and even erosion.

In the viewport, a mask is shown as a colour overlay on the terrain it came from.

Masks from terrain (Data nodes)

Node	White where…
Height Mask	the terrain is between Low and High.
Slope	the ground is between Min and Max degrees steep.
Aspect	slopes face a chosen direction, such as sunny or shaded sides.
Curvature	there are ridges and peaks (convex) or valleys and hollows (concave).
Occlusion	the sky is open; dark in hollows and creases.
Flow	rain would run: streams and rivers. Also outputs flow direction and drainage basins.
Wetness	the ground is damp, near water or where water collects.
Rock Hardness	beds are hard (for erosion's Rock hardness input).

Reshaping masks

• Select Range picks a band of values out of any mask.
• Distance makes a glow around (or inside) the white areas of a mask.

Masks from simulations

Most simulation nodes output masks alongside their heights: Hydraulic Erosion outputs Flow, Wear, Deposition and Sediment; Rivers outputs River and Riverbank; Sea outputs Sea, Shallows and Shoreline; Snow outputs Snow. These are often the most natural masks for colour and vegetation.

Using masks

• Combine takes an optional mask that limits where it applies.
• Settings with a mask port scale their value by a mask. See mask ports.
• Colour: Colourise turns a mask into colour, and Colour Layers and Blend Colours paint through masks.
• Vegetation: populations take Water, Snow, Allowed area and Occupied masks.
• Engines: Splat Map and Pack Masks turn masks into engine-ready textures.