Mesh retopology for adhering to polygon limits in mobile games
Sculpture from ZBrush or Nomad exits with 2–5 million polygons. Mobile game needs 3–8 thousand. Simply decimating through Decimate Modifier in Blender or ZRemesher – not an option: automatic tools don't account for animation, UV unwrapping, and how mesh deforms under skinning.
Retopology – manual (or semi-manual) process of building new, clean mesh over high-poly original. Result must simultaneously satisfy three requirements: fit polygon budget, support correct animation deformation, and provide clean UV unwrap without artifacts.
Where automation breaks and why manual topology is needed
ZRemesher (ZBrush) and Instant Meshes produce quad mesh, but don't think about loops. On character, loops should wrap around mouth, eye sockets, finger joints – following anatomical logic, not uniform grid. If edge loop crosses mouth corner incorrectly – animation produces fold or, worse, mesh visually tears.
For mobile VR on Quest, joints are especially critical: shoulder, elbow, knee, wrist. Here needed edge loops parallel to bone rotation axis – this provides correct deformation distribution under weight painting. Typical mistake after ZRemesher – diagonal loops at elbow that produce triangular artifacts on arm bend even with good skinning.
Decimation Master in ZBrush preserves shape better than ZRemesher, but produces triangular mesh. Triangular mesh can't texture properly through UV-seam without artifacts, and difficult to work with on further edits. Only suitable as intermediate step for baking, not final game-ready asset.
How retopology builds for mobile constraints
Process starts with defining polygon budget by zones. Typical distribution for VR-character on Quest:
- Head + neck: 2000–3000 triangles
- Torso: 1500–2500
- Arms (hands – most expensive): 1500–2000
- Legs: 1000–2000
- Secondary details (clothing, accessories): remaining budget
Tools: RetopoFlow for Blender (best option for manual retopology with surface magnet), Maya Quad Draw for Maya pipeline users. In ZBrush – ZSphere retopology as alternative, but slower.
Key principles most commonly violated:
- No triangles and N-gons in deformation zones. Only quads. Triangles acceptable in static zones: sole, back of neck, immobile elements.
- Edge loops on mouth slit and eyelids – not stylistic choice, requirement: without them blend shapes for mimicry don't work correctly.
- Mesh density adaptive: higher on face, lower on back. Uniform mesh – sign of automation.
After retopology – bake normal map from high-poly to low-poly in Marmoset Toolbag or Substance Painter. This returns visual detail of original without polygon cost.
How long this takes
| Object | Estimated timeline |
|---|---|
| Character head (head only) | 4–8 hours |
| Full humanoid character | 1–3 business days |
| Character with clothing and accessories | 3–5 business days |
| Complex prop / vehicle | 1–4 business days |
Timeline depends on complexity of original sculpture, number of animated zones, and UV requirements. Cost calculated individually.