Terrain

Terrain is a heightmap surface you sculpt and paint in the viewport. It is an authoring layer, not a second renderer: the grid is baked into the same chunk format as blockout geometry, so it inherits chunk culling, retained packets, precomputed visibility, geometry streaming and the lighting bake without a separate runtime path.

Create one from GameObject > Terrain or Project > Add > Terrain. The asset lands under assets/Terrain/ and an actor that renders it is added to the scene with baked lighting and static geometry already on.

The grid

A terrain is a grid of square cells. Heights live on the cell corners, materials on the cells. The whole grid is centred on its actor.

Heights are stored in Q8, which is one 256th of a unit and spans exactly the ±128 local units a chunk vertex can encode. The authored payload is binary, so a 32 x 32 terrain is about six kilobytes: a brush stroke rewrites that, not a mesh document, and undo can afford a snapshot of the whole grid per stroke.

Sculpting

Open the Terrain window and drag in the Scene view. One stroke is one undo entry and one save, taken when the mouse is released.

[ and ] resize the brush. Falloff is Smooth, Linear, Sharp or Constant; Constant has no rim, which is how flat platforms and hard edges are cut.

The brush is drawn on the surface as a green disc that follows the relief, brighter where the falloff bites hardest, with a rim at the radius. Brushes and falloffs are icon strips with tooltips; the active one is highlighted.

While the terrain tool is stroking it owns the viewport, so selection and the transform gizmo stay out of the way. Close the window to get them back.

The Blockout window has the same brush under Build / Edit > Sculpt selection, applied to authored vertices instead of a grid. It displaces along Y under the brush and splits any quad the displacement bends, because a blockout face has to stay planar. Use it to bend existing geometry; use Terrain for ground you want to paint and stroke.

Surfaces

A new terrain adopts the engine's own ground atlas, so it draws grass immediately and a path can be painted without sourcing art first. The atlas is written into the project at assets/Terrain/EpokTerrainAtlas.png the first time a terrain is created, and behaves like any imported texture afterwards: inspect it, reimport it, or replace it in place with your own art.

It holds sixteen 64-pixel tiles in one 256-pixel page, one material per row:

Autotiling

With Autotile borders on, the painted byte is a material row and the baker picks the column and the rotation from each cell's four edge neighbours. You paint a path; its borders resolve themselves.

The transition tiles are painted art, not a runtime blend: the console has no multitexturing, so a material can only change at a cell boundary and the gradient has to live inside the tile. That is why an autotiled atlas must be four tiles wide, with row 0 as the base every overlay transitions onto.

Rotation follows the renderer. At rotation 0 a tile is seen with its top edge toward -Z, and each step turns it a quarter clockwise, so the base material sits to the north, east, south or west. Transition art is drawn with the base at the top, and at the top-right for the corner shapes.

Four shapes per material is a deliberate reduction, and two cases fall outside it. A cell whose opposite neighbours both differ is a one-cell strip, and an isolated cell has no border at all; both stay filled rather than take a mis-rotated border. A cell surrounded by its own material but with several differing diagonals can only show one inner corner. Widen the feature by a cell where that matters.

Merging compares resolved tiles, not painted materials, so two cells of one material that resolved to different borders never merge into one stretched quad.

Turn autotiling off for an atlas of your own that is not laid out this way; the painted byte is then the tile index, and the Surface tab shows the whole atlas as a clickable grid laid out like the texture.

One material covers the whole terrain, so the ground is a single texture page. Painting picks a tile inside that texture's atlas rather than swapping materials. A 2 x 2 atlas on a 256-pixel texture gives four 128-pixel tiles; an 8 x 8 atlas gives 64 tiles of 32 pixels.

Tiles are inset by half a texel, because the console's sampler has no clamp and adjacent tiles would otherwise bleed into each other. Tile rotation is fixed per stroke, or Scatter, which picks a deterministic rotation per cell so a repeating ground texture stops reading as a grid.

There is no per-pixel blending between tiles: the hardware has no multitexturing. Author transitions as their own tiles in the atlas, and use baked corner colours for the rest.

Lighting is baked. A terrain actor is created with Baked lighting because that is what terrain wants: per-corner light and ambient occlusion computed once, costing nothing per frame, with fog modulating it at runtime. The quad normal is the average of its four corner normals, which softens the boundary between adjacent cells; true per-corner shading would need a normal per corner, which the cooked quad format does not carry.

Budgets

The Budget tab reports the figures that decide whether a terrain fits.

• Quads. One per cell, before merging. The whole scene has a resident budget of 3500 quads (7000 triangles); terrain competes for it with every other mesh. A 32 x 32 terrain is 1024 quads and leaves room for props.
• Chunks. Draw chunks are what the per-chunk bounds test pays for every frame, and a fine grid produces many of them. A chunk holds at most 96 quads and must span under 16 units, so the baker uses the largest block of cells that fits: three cells at 4 units, seven at 2 units, fifteen at 1 unit.
• Collider. Two bytes per grid corner. A 32 x 32 terrain costs about 2 KiB.
• RAM. Measured on the sample project, replacing its ground slab with a 32 x 32 terrain at 4 units, baked lighting and heightfield collision on, raised static RAM from 899 KiB to 1.24 MiB out of the console's 2 MiB. That is roughly 370 bytes per quad: the cooked quad and its positions, the baked corner colours, and two retained packets per triangle per field. Turning Retained Packets off in Project Settings trades that back for per-frame packet building. Measure your own scene; this is one configuration.

Cells are alabeado — a cell's four corners need not be coplanar. The renderer splits every quad into two triangles anyway, so a bent cell costs the same as a flat one and half of what two triangle faces would.

Merging

Merging collapses a block of coplanar cells that share a tile into one quad. It is the only decimation the cooked format allows, because geometry is baked into fixed arrays and nothing can be decimated at runtime. On ground with flat plains and uniform slopes it removes a large fraction of the quads at no visual cost.

It stretches the tile across the merged cells, which is why it is off by default. A merged quad never straddles two chunks, and cells with different tiles never merge.

Limits

• A terrain spans at most 256 units per axis. Beyond that a vertex leaves the local window the chunk compiler encodes.
• A single cell must stay within about 16 units on every axis, including height. Author a cliff as several cells rather than one tall step; the build names the offending cell if you do not.
• Heightfield collision indexes the grid from the collider box's world minimum, so the actor must be translated only — no rotation, no scale. Change the cell size instead of scaling the actor. A rotated terrain is still drawn; the build only refuses to cook a collider for it.
• The heightfield is a surface to stand on, never an obstacle, exactly like the ramp collider. A character is lifted onto it rather than pushed sideways by it, which is what lets a slope be walked up from any side.
• Terrain is 2.5D. Caves, overhangs and holes are blockout geometry.

Navigation and streaming

Add a NavigationSurfaceComponent to a terrain actor to feed its walkable surface into the navigation bake. The bake consumes the same quads the renderer draws, so a merged cell contributes one wide triangle pair rather than the cells it replaced, and the 4096-triangle bake limit applies. A terrain's own heightfield collider is exempt from the rule that a navigation surface must have its box collider disabled, because it is a surface rather than an obstacle.

Geometry streaming covers terrain exactly as it covers editable meshes: chunks are packed into 64 KiB pages and read on demand. See Geometry streaming.