The 3D Handbook
Part 4 — Modeling OptimisationPage 105 of 248 on the reading route
Topic

Retopology

Building a new, cleaner and lighter mesh over a dense one, by hand or with auto-retopology tools, and when environment artists actually need it.

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Retopology is building a new mesh over an existing one so it has a cleaner, lighter structure. GarageFarm's guide defines it as "reorganizing and optimizing the polygonal structure of a 3D model", usually turning a dense sculpt into a lower-polygon version (GarageFarm.NET blog: Retopology: A Comprehensive Guide to 3D Model…).

The new mesh follows the old surface but has edge flow you chose: edge loops where they help, few triangles where nothing happens, and a layout that is easy to UV and bake.

#Reasons to retopologise

Sculpts and scans are dense and irregular. They hold fine detail well but are too heavy for real-time use. Retopology fixes three problems (GarageFarm.NET blog: Retopology: A Comprehensive Guide to 3D Model…):

  • Triangle count: it reduces the polygon count for "real-time applications such as video games". See polygon and triangle budgets.
  • Deformation: clean topology "ensures that the topology flows smoothly around joints and deformation areas".
  • UVs: it gives "a clean mesh that makes UV mapping more straightforward and efficient".

The detail of the original is then transferred to the new mesh by baking normal and other maps, the core of the the high-to-low workflow.

#When environment artists need it

Environment artists retopologise less than character artists. Much of an environment is static, so decimation is often good enough. You will still retopologise:

  • hero props that need clean shading and good UVs (see hero assets, props and filler);
  • sculpted modular pieces such as carved trims, columns and arches, where clean edge loops make the piece easy to edit, UV and snap;
  • anything that moves or bends: doors with soft parts, cloth, banners, foliage that sways;
  • assets for VR, mobile or other non-Nanite targets, where triangles are scarce. A Quest 2 frame is recommended to stay under 750,000 triangles (Meta Horizon Developers: Device Optimization Comparison), so each prop's triangle count has to be justified.

#Manual retopology

GarageFarm describes manual retopology as "the artist painstakingly creating new polygons over the surface of the high-resolution model": most control, most time (GarageFarm.NET blog: Retopology: A Comprehensive Guide to 3D Model…). Common tools, as described in the same guide (GarageFarm.NET blog: Retopology: A Comprehensive Guide to 3D Model…):

  • Maya Quad Draw, called "one of the most powerful manual retopology tools available", with a Live Surface mode that snaps new geometry to the high poly.
  • RetopoFlow for Blender, with Contours, PolyStrips and Strokes tools.
  • Blender built-ins: Poly Build to add polygons directly on a surface, Bsurfaces to draw topology with curves, and the Shrinkwrap modifier to project vertices onto the high poly.
  • 3ds Max Graphite Freeform tools and the WrapIt plugin.
  • ZBrush Topology brush, which draws new topology directly on the sculpt.

#Automatic retopology

"Automatic retopology uses algorithms to generate a new, optimized mesh" (GarageFarm.NET blog: Retopology: A Comprehensive Guide to 3D Model…). It is fast but can behave unpredictably where complex deformation is needed (GarageFarm.NET blog: Retopology: A Comprehensive Guide to 3D Model…).

A photogrammetry head from Captured Dimensions, cleaned up, retopologised and baked. The studio notes it was either ZRemeshed or decimated and may not be ready for animation, which shows the trade-off between automatic and manual retopology. Inspect the wireframe around the eyes and mouth and ask whether those loops would deform well.Captured Dimensions, via Sketchfab
Three versions of the same curved surface patch side by side. Left: a dense, irregular triangle mesh labelled sculpt or scan. Middle: a lighter but irregular triangle mesh labelled decimated. Right: a light quad mesh with loops following the curve, labelled retopologised.
Decimation keeps the shape but leaves chaotic triangles. Retopology rebuilds the surface with deliberate loops, at the cost of time.Diagram by the handbook author

#A typical workflow

  1. Decide the budget from screen size and platform (see polygon and triangle budgets).
  2. Block the big loops first: silhouette edges, hard edges and UV seams.
  3. Fill in with an even quad flow, adding density only where the silhouette or deformation needs it.
  4. Check the silhouette against the high poly from the angles players will see.
  5. UV, then bake the high poly onto the new mesh (see UV mapping and baking).
  6. Make LODs from the result, often with decimation.
engine9's rework of an original Sketchfab model by Alexey Lvov, made by retopologising it and baking the original's textures onto the new mesh, the same steps as the workflow above. Compare its wireframe with the original model linked from its Sketchfab page.engine9, via Sketchfab

#Common mistakes

  • Retopologising everything. Rocks, rubble and debris rarely need clean quads; decimate them.
  • Even density everywhere. Spend vertices on the silhouette and curvature, not on flat areas.
  • Ignoring UV seams. Plan seams while you draw loops, so islands unwrap flat.
  • Too far from the surface. Large gaps between low and high poly cause baking errors (see fixing baking artefacts).
  • Trusting auto output blindly. Check poles and spirals on curved parts (see pole).

#In different tools

#Further reading and watching

Embedded in GarageFarm's retopology guide as its ZRemesher example; watch it alongside Maxon's ZRemesher reference. Watch on YouTube
Embedded in GarageFarm's guide as its Quad Draw example; good for learning a manual workflow in Maya. Watch on YouTube
Embedded in GarageFarm's guide as its RetopoFlow example; useful if you retopologise inside Blender. Watch on YouTube
A quick, free route to an automatic quad base, as featured on BlenderNation. Watch on YouTube

References

  1. GarageFarm.NET · Retopology: A Comprehensive Guide to 3D Model Optimization · GarageFarm.NET blog · article · accessed 2026-10-20
  2. Meta · Device Optimization Comparison · Meta Horizon Developers, 2026 · docs · accessed 2026-10-20
  3. Maxon · ZRemesher (Reference Guide) · ZBrush Documentation, 2026 · docs · accessed 2026-10-20
  4. Maxon · ZRemesher (User Guide) · ZBrush Documentation, 2026 · docs · accessed 2026-10-20
  5. Simón Sánchez · Free Auto Retopology with Instant Meshes · BlenderNation, 2019 · article · accessed 2026-10-20
  6. Epic Games · A first look at Unreal Engine 5 · Unreal Engine blog, 2020 · article · accessed 2026-10-20
  7. Epic Games · Nanite Virtualized Geometry · Unreal Engine Documentation, 2026 · docs · accessed 2026-10-20
  8. Epic Games · Nanite Technical Details · Unreal Engine Documentation, 2026 · docs · accessed 2026-10-20
  9. Epic Games · Bringing Nanite to Fortnite Battle Royale in Chapter 4 · Unreal Engine tech blog · article · accessed 2026-10-20

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Last updated 2026-10-22