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Mask Filters is an advanced system for defining where objects spawn. Each filter generates a grayscale mask over the terrain, and multiple filters can be stacked and blended together to create complex spawn rules. Mask Filters work exclusively with Unity Terrain and are evaluated on the GPU, making them faster and more powerful than simple filters for terrain-based workflows. They support blending operations between filters (Multiply, Add) and include advanced filters like Aspect, Concavity, and Smooth that are not available in simple filters. Mask Filters panel in MegaWorld.

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How It Works

Each filter in the stack produces a mask (black = no spawn, white = spawn). Filters are applied in order:
  • The first filter in the stack always starts fresh (Multiply mode is applied automatically).
  • Every subsequent filter blends its result with the previous mask using the Blend Mode you set.
Blend Modes:
  • Multiply — combines masks multiplicatively. The result can only be equal to or smaller than either input. Use this to narrow down the spawn area.
  • Add — combines masks additively. The result can only be equal to or larger than either input. Use this to expand or union spawn areas.

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Simple filters vs mask filters

Filter Settings are split into two workflows:
  • Simple Filters are lighter and work with any mesh, not only Unity Terrain.
  • Mask Filters are terrain-focused, GPU-evaluated, and support blendable mask operations for more advanced control.

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Simple Filters

Simple Filters panel in MegaWorld. Simple Filters visualization in MegaWorld.

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Mask Filters

Mask Filters stack in MegaWorld. Mask Filters visualization in MegaWorld.

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Available Filters

Height Filter

Spawn within a defined height range with smooth falloff edges.

Height Noise Filter

Height filter with noise applied to the edges for a natural, irregular look.

Slope Filter

Spawn within a defined slope angle range.

Noise Filter

Add fractal noise to break up uniform spawn patterns.

Textures Filter

Restrict spawning to specific terrain texture layers.

Concavity Filter

Target recessed or exposed terrain features like valleys and ridges.

Aspect Filter

Target terrain faces pointing in a specific direction.

Smooth Filter

Blur the current mask to soften hard edges.

Expand Filter

Dilate the current mask outward.

Expand Down Filter

Dilate the mask downward only, respecting terrain height.

Image Filter

Use a custom texture as a mask.

Mask Operations Filter

Apply mathematical operations to the current mask (invert, clamp, remap, etc.).