Auto Unwrap

Auto Unwrap lays a curved surface out flat on the texture in a few large pieces, called charts, with little stretching. Use it on creatures, characters, statues, rocks and cleaned-up AI models. On shapes like these, Smart UV would cut the surface into dozens of small islands. Put it after Polyreduce and before Bake or the first paint node.

Smart UV or Auto Unwrap?

Smart UV projects flat groups of faces straight onto the texture. On crates, walls, buildings and other hard-surface props that gives clean, square islands with no stretch.
Auto Unwrap grows each chart over the surface while it stays within the Angle limit of the chart’s overall direction. It then flattens the chart the way a map flattens a globe, keeping the shapes of the triangles. A chart that would fold, overlap itself or stretch more than the Stretch limit is cut in two and each half is flattened again. Finally, neighboring charts are joined wherever the two still lie flat together within the Stretch limit without sprawling, so a bumpy surface ends up in far fewer, larger charts.

On AI-generated models reduced to 10,000 triangles, Auto Unwrap made 2.5 to 19 times fewer charts than Smart UV. A squirrel character went from 463 islands to 51, and a detailed stone from 2,036 to 505.

Choosing the seams

By default Auto Unwrap decides every seam itself. To decide them yourself, pick an edge selection in Seams: every area your cuts enclose is laid out as one island where it can be, and no island crosses a cut. A cut that ends inside an area (a slit) is cut open inside its island. Where an island would stretch past the Stretch limit, Auto Unwrap first cuts a short slit into it from its edge; only if that isn’t enough does it split the island in two. Islands laid out this way never fold or overlap themselves.

On a character, put Character Seams first and pick its seams selection: the face, the body and every limb come out as islands of their own, instead of charts that run across the face. Any edge selection works, for example one from a Selection node. If the selection isn’t on the incoming mesh, Auto Unwrap unwraps without it and shows a warning. The edge selections on the mesh, seams and extra_seams included, come out of Auto Unwrap unchanged, so a later node can still use them.

How the charts are packed

Every chart keeps its true size, so a centimeter of surface gets the same number of texels everywhere and no chart looks blurrier than its neighbors. Auto Unwrap then fits the charts together by their real outlines, turning each one whichever way sits tightest. Small charts drop into the gaps beside the big ones, and the whole layout grows as large as the texture allows. On AI models at 10,000 triangles, this covers 57 to 71% of the texture.

Margin is the smallest gap between two charts, as a share of the texture’s width. The default, 0.004, is about 8 pixels on a 2048 texture and 4 on a 1024 one. Charts also keep half a margin from the texture’s edge. If the margin is too wide to fit that many charts, Auto Unwrap packs them with a narrower one and shows a warning.

Bake after unwrapping

Auto Unwrap replaces the mesh’s UVs, so any texture it had no longer lines up. To keep an imported model’s look, add a Bake after it. Wire the unwrapped mesh as the target and the mesh from before the unwrap as the source. Bake copies the textures onto the new layout.

The shading stays as it was: Auto Unwrap keeps the mesh’s normals, so a seam never shows as a crease. Where the mesh shades hard, for example after a Normals node with a smoothing angle, Auto Unwrap prefers to put its chart borders along those hard edges, which is where a baked normal map needs them, and it never joins two charts across one.

Some imported models shade hard along many edges that aren’t real creases. Every one of those edges stays a seam, so the unwrap keeps many small charts. Put a Normals node with full smoothing before Auto Unwrap: on one such model this took the chart count from 631 to 172.

Inputs

Mesh

The mesh to unwrap.

Outputs