Part 4 — Modeling
Box and subdivision modeling, clean topology, hard-surface techniques, modular kits and environment pieces, and how to keep meshes within budget.
Approaches
- Ways to build a 3D modelOverviewA map of the main ways to build a 3D model for games, from box modeling and subdivision to CAD, sculpting, procedural tools, kitbashing, scanning and AI generation, with when to use each.
- Box modelingTopicBuilding a model by starting from a simple primitive and refining it with extrudes, insets and loop cuts, usually with subdivision in mind.
- Extrude, inset and loop cutKey termThe three everyday polygon-modeling operations. Extrude pulls new geometry out of a selection, inset makes a border of faces inside it, and loop cut splits a ring of faces with a new edge loop.
- Subdivision surface modelingTopicModeling a light polygon cage and letting an algorithm, usually Catmull–Clark, compute a smooth surface from it; in games, mostly used for high-poly bake sources.
- Control cage and limit surfaceKey termThe cage is the low-resolution mesh you edit; the limit surface is the perfectly smooth shape that endless subdivision of it would reach. What you see in the viewport is usually somewhere in between.
- Edge creaseKey termA sharpness value stored on edges (or vertices) that tells subdivision to keep them sharp for some or all levels, instead of adding support loops.
- CAD and NURBS modeling for gamesTopicModeling hard-surface objects with exact mathematical curves and surfaces in tools like Plasticity, MoI, Fusion or Rhino, then converting them to polygon meshes for baking or for direct use in a game.
- Procedural modelingTopicBuilding geometry from rules and parameters instead of by hand, in node systems such as Houdini and Blender Geometry Nodes, and handing those rules to level artists as tools inside the engine.
Topology
- TopologyTopicHow a mesh's vertices, edges and faces are connected; "good" topology depends on whether the mesh will deform, be subdivided, be baked or be rendered as it is.
- Edge flowTopicHow a mesh's edge loops follow its form and the way it bends; vital for characters and subdivision, much less important on static props.
- PoleKey termA vertex where three, or five or more, edges meet; poles stop and redirect edge loops and affect how a surface subdivides.
- Edge loopKey termA chain of connected edges that runs straight through quads, vertex to vertex, until it closes on itself or hits a pole or border.
- Edge ringKey termA set of parallel, unconnected edges that cross a strip of quads, each on the opposite side of the same face; the path a loop cut follows.
- Face loopKey termA continuous row of faces lying between two neighbouring edge loops; the strip you select to extrude bands, assign materials or add a loop cut.
- Support loop (holding edge)Key termAn extra edge loop placed close to an edge so that it stays tight when the mesh is subdivided; the alternatives are creases and bevels.
- Smoothing, hard edges and smoothing groupsTopicHow vertex normals decide whether an edge shades smooth or sharp, how 3ds Max, Maya and Blender control it, how engines import it, and why hard edges must sit on UV seams for baking.
Hard-surface modeling
- Hard-surface modelingTopicModeling manufactured, engineered objects such as crates, machines, weapons and sci-fi panels, and the main workflows game artists use to make their edges, shading and detail work in real time.
- BooleansTopicCombining, subtracting or intersecting meshes as if they were solid volumes; a fast way to cut hard-surface shapes, and a common source of messy topology and shading errors.
- Bevels and chamfersTopicSmall cut or rounded strips along a model's edges that catch light like real manufactured edges; built with geometry, baked from a high poly, or faked with a bevel shader.
- Bevel shadersKey termA render-time shading effect that makes sharp edges look rounded by bending normals near them, without changing the mesh. Used in place of modeled high-poly bevels for baking and renders.
- Weighted (custom) normalsTopicCustom vertex normals that let big faces win over small bevels, so bevelled low and mid-poly meshes shade flat and clean without a baked normal map.
- The mid-poly workflowTopicBuilding one moderately dense mesh with real bevels and weighted normals, textured with shared tiling materials, trims and decals instead of a unique high-to-low bake.
- FloatersKey termSeparate pieces of detail geometry, such as screws, vents or panels, that hover just above a high-poly surface instead of being welded into it; the bake records them anyway.
- GreeblesKey termSmall surface details (panels, pipes, vents, boxes) added to a larger form to make it look complex, functional and big. A model-making technique from Star Wars that hard-surface artists still use.
- The high-to-low workflowTopicBuilding a detailed high-poly model and a separate efficient low-poly model, then baking the high poly's surface detail into texture maps for the low poly.
Environment modeling
- Modular kitsTopicSets of environment pieces built on a shared grid so they snap together into many different spaces. How Bethesda, id and others design, test and vary them.
- Glue piecesKey termKit pieces whose job is to join other pieces, cover gaps at odd angles and bridge different kits. Bethesda built whole "glue kits" for this.
- Showcase (warehouse) mapKey termA test level that lays out every asset, kit piece or material in one place, so the team can check scale, consistency and quality in the engine before the content spreads across levels.
- Grids and metricsTopicThe measurements a game is built around (player size, jump height, door width, corridor width) and the snapping grid that keeps every piece consistent with them.
- Gym levels and metrics mapsKey termDeveloper-only test maps that lay out doors, stairs, jumps, ledges and slopes at measured sizes, so designers and artists can feel the player's metrics before building real levels.
- KitbashingTopicBuilding new assets or spaces by recombining existing parts, from film model kits to KitBash3D packs and mixed modular kits in Skyrim. Fast and legitimate, with honest-credit and consistency pitfalls.
- Hero assets, props and fillerTopicHow environment teams sort assets by importance: a few hero assets that anchor a place, secondary props that make it believable, and cheap filler that is reused everywhere. Where to spend detail, and where not to.
- Modeling rocks, trees and terrain piecesTopicHow environment artists build the natural parts of a game world (rocks, cliffs, embankments, caves and trees) as reusable, instanced pieces that sit on terrain, with examples from The Last of Us Part I and The Witcher 3.
- Collision meshesTopicThe simplified, invisible shapes that physics and the player actually touch. How to build them from boxes, capsules and convex hulls, and how Unreal, Unity and Godot import them.
- Convex hullKey termThe tightest shape with no dents that wraps a mesh, like a rubber band or shrink-wrap. Physics engines use convex hulls as cheap, reliable collision; concave objects need several.
- Convex decompositionKey termSplitting a concave mesh into a set of convex pieces so a physics engine can collide with it cheaply. How V-HACD, CoACD and the Unreal, Unity and Godot tools do it, which settings matter, and when to build the pieces by hand.
- Player collision capsuleKey termThe invisible pill shape that represents the player in the physics world. Its radius, height, step height and slope limit decide every door width, stair and ramp in your levels.
Optimisation
- Polygon and triangle budgetsTopicHow many triangles an asset or a frame can afford, with dozens of published examples from real games, platforms and asset types, and a method for setting a budget yourself.
- Level of detail (LOD)TopicSwapping an asset for cheaper versions as it gets smaller on screen, from classic LOD chains and HLOD to impostors and Nanite.
- Impostors and billboardsKey termFlat cards that show pre-rendered views of a 3D object, used as the cheapest distant LOD for trees, rocks and buildings. Billboards use a few fixed views; octahedral impostors pack many views into one atlas.
- Hierarchical LOD (HLOD)Key termLevel of detail for groups of objects. Distant clusters of meshes are replaced by one merged, simplified or instanced proxy, cutting draw calls and keeping unloaded areas visible.
- InstancingKey termDrawing many copies of the same mesh and material in one batch, with only position, rotation, scale and a little custom data stored per copy. This is why kits, rocks and forests are cheap to draw.
- RetopologyTopicBuilding a new, cleaner and lighter mesh over a dense one, by hand or with auto-retopology tools, and when environment artists actually need it.
- DecimationKey termAutomatically reducing a mesh's triangle count while keeping its shape, usually producing messy triangles rather than clean quads.