Unity Terrain Authoring: Coordinate Shape, Surface Layers and Openings

Start with the heightfield representation

Unity Terrain stores surface heights in a rectangular array represented by a heightmap. Sculpting tools modify that height information. The representation supplies one surface height at each horizontal sample, so a cave ceiling above a floor cannot be expressed simply by sculpting that same heightfield. Plan separate geometry where the desired shape needs overhangs or enclosed space. This limitation follows from the representation, rather than from brush quality. [1]

Block out a connected route

Imagine a hiking level assembled from adjacent terrain tiles. For an illustrative layout, each tile is 200 world units wide and the pair spans 400 world units. A path crosses their shared edge before reaching a cave entrance. Establish tile placement, terrain dimensions, and a usable walking route before adding detailed surface painting.

Inspect the shared boundary from above and from player height. Adjacent edges must describe the intended continuous surface; a matching grass texture cannot repair a geometric step. After reshaping the route, check the boundary again. Treat slope, width, and sightlines as level-design decisions that need play review, not consequences that a heightmap automatically gets right.

Author reusable surface definitions

A Terrain Layer is an asset containing textures and surface properties used by the terrain material. Layers can be reused across tiles. The first assigned layer covers the terrain as its base; subsequent layers can be painted over selected regions. [2]

For the hiking route, choose a shared grass base and a dirt-path layer. Review texture tiling at player distance and where the path crosses the tile edge. Changing a shared layer should be an intentional change to every place using that asset. Also inspect newly added tiles: applying their first layer fills the whole tile, which can be surprising when the artist intended only a small dirt stroke. [2]

Make a hole into an authored entrance

Paint Holes changes a terrain surface mask. It removes the marked terrain surface rather than constructing cave walls or a ceiling. Add the entrance geometry and its required collision deliberately, and use surrounding rock geometry to hide undesirable mask-edge aliasing if needed. [3]

In the cited Unity 6.0 workflow, URP projects must enable Terrain Holes in the URP Asset for holes to remain in a build. A custom terrain material also needs to honor the hole mask. Confirm both the editor view and a representative build rather than treating an editor opening as sufficient evidence. [3]

Review the resulting level contract

Walk the complete route, including the tile boundary and the transition onto cave geometry. Look for steps, visible gaps, mismatched texture scale, unexpected base-layer coverage, and collision that disagrees with the opening. Recheck these cases after edits to shared layers or terrain heights.

Terrain Layer options and rendering costs depend on the material and render pipeline. Keep the authored layer set purposeful and inspect the target configuration before copying settings from another pipeline. These review steps describe a proposed workflow; no performance or traversal test has been claimed. [2]

Sources

1. Working with Heightmaps — Unity Technologies.
2. Terrain Layers — Unity Technologies.
3. Paint Holes — Unity Technologies.