Subdivision Levels

Subdivision levels let you sculpt fine detail on a much denser version of the Generated Mesh while the base mesh — the created topology, with its UV map — stays as it is. When the detail is done, Bake Detail turns it into a normal map and a height map on the base. The controls are in the Subdivision Level accordion of the Sculpt tab, whose title shows the level you are on (for example Subdivision Level: 2).

Levels live on the Generated Mesh

Subdivision levels belong to the Generated Mesh, and the controls appear only while it is on screen. Otherwise the accordion says Subdivision levels live on the Generated Mesh. Rebuild the model above, then switch the viewport to the Generated Mesh to add levels to it. You can also create the Generated Mesh in the Retopology tab.

With no levels yet the accordion reads Subdivision levels: none. Once you have some, it reads Subdivision level n of m with the number of faces at the top level. Level 0 is the base mesh. The level shown stays shown when you switch to another tab.

How the levels relate

• Each level is the one below it subdivided: every face split into four and smoothed (Catmull-Clark). A triangle becomes three quads.
• Each level keeps its own sculpted detail, measured from the smooth surface it was subdivided into.
• Sculpting a lower level moves every level above it, with their finer detail riding along on the moved surface. Sculpting a higher level never moves the ones below it.
• Vertex colours and painted channels follow you between levels: going up, they spread over the new points the way the surface does.

Controls

Control	What it does
Subdivide	Adds a level above the top one and shows it. Every face is split into four and smoothed. If you are on a lower level, it goes to the top level first.
Lower	Shows and sculpts one level down. Changes made lower carry the finer levels' detail with them. Disabled on level 0.
Higher	Shows and sculpts one level up. Disabled on the top level.
Delete Higher	Throws away every level above the one shown.
Bake Detail	Bakes the top level's detail into the base mesh's UV map: a normal map, and a height/displacement map for the renderer to subdivide. The base mesh is shown while it bakes.

Delete Higher and Bake Detail are disabled until there is at least one level above the base.

A typical workflow

1. Make the Generated Mesh: retopologize the model, or use Rebuild in the Sculpt tab's Rebuild Method accordion. Before you rebuild, that accordion shows what building the level will take at its peak against the memory free now (Peak ~… while building, … free) — see Rebuild & Repaint.
2. Give the base mesh a UV map (see Generate UV Map). Bake Detail bakes into it.
3. Switch the viewport to the Generated Mesh and press Subdivide once or several times.
4. Sculpt fine detail on the top level.
5. Press Lower whenever you want to change broad forms; the fine detail moves with them. Press Higher to go back.
6. With the materials selected, press Bake Detail. When it finishes, the status line says Baked the subdivision detail into the base's normal and height maps.

Bake Detail bakes the selected materials that have a UV map. If none do, the status line reads Selected material(s) need a UV map first. If there is no level above the base, it reads Subdivide and sculpt first: there is no detail above the base to bake.

How many levels you can have

Every level has four times the faces of the one below, so the limit is set by face count, not by a number of levels. Subdivision level ceiling (million faces) in Settings > Memory Settings sets the most faces one level may have, from 1 to 1024 million. From a 20 thousand face base, 4 million allows three levels and 24 million allows five. If another level would go over the ceiling, Subdivide refuses and the status line says how many faces it would have had. What the ceiling really governs is whether sculpting stays interactive at that density, which depends on your machine.

What changes or ends the levels

• A new Generated Mesh (for example a new retopology) ends the levels.
• Changing level rebuilds the Generated Mesh on screen, so its sculpt layers and its sculpt undo history are cleared each time you press Subdivide, Lower or Higher.
• While a UV map or a bake is being made, level changes are refused with Subdivision levels: wait for the UV map or bake to finish. UV work needs the base's UV map, so a higher level is set aside on the base while it runs and comes back on screen when it is done.
• Dynamic topology works on the Loaded Mesh only, so it never changes the Generated Mesh's levels.