Seam Tools

Seam Tools lets you choose where the UV map is cut instead of leaving every decision to the unwrap engine. You mark edges on the Generated Mesh by hand, extend a mark around a whole edge loop with one click, or let Suggest Seams propose a set from the shape of the mesh. The marks are used the next time you run Generate UV Map with an engine that reads them. Open the window from the Window menu → Seam Tools.

Opening the window

Seam Tools is a floating window you can move and arrange on its own, like Selection Tools. It works on the Generated Mesh only, so until you have retopologized or passed through at least one material it just shows a reminder to do that first. The Loaded Mesh never carries seam marks.

Marking seams by hand: Edit Seams

Click Edit Seams to switch the mode on; the button reads Editing Seams while it is active, and clicking it again turns it off. By default Shift+E toggles the mode from the keyboard.

While the mode is on and the Generated Mesh is on screen:

• Move the cursor over the mesh and the edge nearest to it is highlighted as a preview, so you can see exactly which edge a click will hit.
• Click an edge to mark it as a seam. Clicking a marked edge unmarks it.
• Alt+click an edge to mark it and extend the mark along its whole edge loop in both directions. On quad topology the loop follows the quad edge flow; on a Pass Through (triangle) piece it follows the straightest continuation. The walk stops at the mesh boundary, at hidden faces, or where the loop closes on itself. Alt+click only ever adds marks.
• Clicking empty background still orbits. Because a bare Alt is reserved for loop extension in this mode, use Ctrl+drag to orbit over the mesh.

If the Loaded Mesh is on screen instead, clicks select faces as usual — Edit Seams only takes over the click on the Generated Mesh. Marked edges under the buttons shows how many edges are currently marked.

Suggest Seams

Suggest Seams runs a single geometry pass over the Generated Mesh and marks the edges where it changes direction. It is a starting point to refine with Edit Seams, not a finished seam layout. The result is added to whatever is already marked, so it never erases edges you placed by hand. Edges on the mesh boundary are left alone, since they are island edges anyway.

Setting	What it does	Default	Range
Sharp angle	Any interior edge whose two faces bend past this angle is suggested as a seam. This pass always runs.	50°	1–180°
Coplanar clustering	Adds a second pass that groups faces into flat regions and suggests a seam wherever two regions meet. It catches softer transitions, such as a rounded box corner, that stay under the sharp angle but still separate two distinct sides.	On	—
Flat region angle	Used when Coplanar clustering is on. Faces stay in the same region as long as each step to a neighbour bends by no more than this angle, so a gently curving surface stays as one region instead of being cut edge by edge.	15°	1–179°

Lower Sharp angle to cut at gentler creases; raise Flat region angle if a curved surface is being split into too many regions.

Clear All Seams

Clear All Seams removes every mark on the Generated Mesh at once, so you can start over. By default Alt+E does the same from the keyboard. The button is greyed out while nothing is marked. There is no confirmation.

Saving and loading seams

Seams are not saved automatically. Save Seams writes the current marks to a .seams file named after the loaded model and stored next to it (<mesh name>.seams), replacing any earlier one. Load Seams reads that file back. The file only fits the Generated Mesh it was saved from: if the Generated Mesh now has a different number of faces, loading is refused with a message instead of putting marks on the wrong edges.

Marks belong to the Generated Mesh exactly as it is. Anything that rebuilds it, such as retopologizing or passing through another material, clears every mark. If you delete one material's generated polygons, the marks on the remaining materials are kept. It is easiest to place seams once the Generated Mesh is complete.

Which UV engines use the marks

Marked seams are forced cuts for two of the engines in Generate UV Map:

• Field-Guided (natural seams) keeps its own choice of seams and adds your marks as cuts it must make, alongside the boundaries of any Selection Tools color groups you have painted.
• Grid Unwrap (instant, quad meshes) treats every marked edge, together with the mesh boundary, as a wall it never unfolds across. This is what lets it handle anything rounder than boxy hard-surface topology: cut a cylindrical limb or a closed shell into pieces small enough to lie flat, and Grid Unwrap can lay them out.

Controls

Control	What it does
Surface Cords (prototype)	Opens a prototype tool for drawing connected polygon-edge cords and filling selection groups. It lasts for the current session only.
Edit Seams / Editing Seams	Turns edge-marking mode on or off. Click marks or unmarks an edge; Alt+click marks the whole edge loop. By default Shift+E.
Clear All Seams	Removes every mark. By default Alt+E.
Marked edges	How many edges are currently marked.
Save Seams	Writes the marks to <mesh name>.seams next to the loaded model.
Load Seams	Reads the marks back from that file.
Sharp angle	Bend angle above which Suggest Seams marks an edge.
Coplanar clustering	Also suggests seams where flat regions meet.
Flat region angle	How far neighbouring faces may bend and still count as one flat region.
Suggest Seams	Runs the suggestion pass and adds its result to the existing marks.

Both shortcuts can be rebound in the Keyboard Setting tab.

Edition availability

Seam Tools is part of Vertexix and Ultra. In Free and Light the window opens, but Edit Seams, Clear All Seams and Surface Cords (prototype) are locked, and the count, Save/Load and Suggest Seams controls are not shown. Those editions only offer the Lightmap engine, which ignores marks anyway.