The 3D Handbook
Part 8 — Building in the engine
Chapter

Worlds

Read these pages in order, or jump to the one you need.

  1. Terrain and landscapesTopicHow heightmap terrain works in Unreal, Unity and Godot; landscape sizes and components, heightmap bit depth, terrain texturing with layers and virtual textures, generating terrain in World Machine and similar tools, and how Far Cry handled terrain at open-world scale.
  2. Terrain layers and splat mapsKey termHow terrain materials such as grass, rock and mud are painted onto a landscape, with weight maps (splat maps) that store how much of each layer covers every point, or index maps that store which layers do.
  3. Blending meshes into terrainTopicWays to hide the hard line where rocks, cliffs, roads and buildings meet the ground: shared world-space materials, vertex-painted transitions, runtime virtual textures, distance-field and depth-based blends, matched normals and decals at the seam.
  4. Pixel depth offsetKey termA material output that pushes each pixel's depth back from the camera, so other surfaces win the depth test there; used to soften intersections with a dither and to let parallax-mapped surfaces intersect correctly, at a cost.
  5. Heightfield erosionKey termSimulating water and weathering on a terrain heightmap to carve valleys, gullies and sediment fans, and exporting masks of where material was removed and deposited for texturing and scattering.
  6. Foliage and vegetationTopicHow games build and draw trees, bushes and grass; alpha cards versus modelled leaves, instancing, culling and billboards in Unreal, Unity and Godot, the costs of wind animation, and what Fortnite, Ghost of Tsushima and Horizon Zero Dawn did.
  7. Wind and world position offsetKey termAnimating foliage, cloth and props by moving vertices in the material (World Position Offset, or vertex animation), driven by masks, pivots and a wind signal; cheap per object but with costs for shadows, culling and GI.
  8. Vertex animation textures (VAT)Key termBaking a simulation or animation into textures that a vertex shader plays back on a static mesh; how Houdini's Labs VAT and Blender's OpenVAT export them, how Unreal and Unity play them back, and what they are used for.
  9. Water surfacesTopicHow real-time water is shaded and built (depth colour, refraction, reflection, foam and flow maps), the engine tools for it in Unreal and Unity, how Houdini generates flow maps, and how Valve and Rare built water for shipped games.
  10. Procedural placement and scatteringTopicPlacing trees, rocks and props by rules instead of by hand; how scatter graphs work, random versus Poisson disk distributions, ecosystem simulation, Unreal PCG, Houdini, Blender and Godot, and how Horizon Zero Dawn and Far Cry 5 used it.
  11. Level streaming and World PartitionTopicHow large worlds load piece by piece around the player; Unreal Engine 5's World Partition grid, streaming sources, Data Layers, One File Per Actor and HLOD, Unity's additive scenes, and what environment artists need to set and check.
  12. Poisson disk samplingKey termScattering points at random but never closer than a minimum distance, which avoids the clumps and gaps of pure randomness and looks like natural spacing; Bridson's algorithm does it in linear time.
  13. Virtual texturingKey termSplitting huge textures into small tiles and keeping only the visible ones in memory; streaming and runtime virtual textures in Unreal and Unity, what they cost, and how id Software and Far Cry used them for terrain.
  14. Virtualised geometry (Nanite)TopicHow Unreal's Nanite streams and draws only the triangle detail the screen can show, what it supports in current versions, what it costs, and when not to use it.
  15. Gaussian splattingTopicWhat 3D Gaussian splatting is, how captured photos become millions of soft ellipsoids, real performance and memory numbers in Unity, the state of Unreal plug-ins and the glTF standard, licensing traps, and where splats do and do not fit in game production.