Edges: selecting and creasing edges

Tool > Geometry > Edges selects edges of a Part's base mesh: one by one, as whole edge loops, along open borders, or every hard edge at once by the angle between its faces. The selection is what edge creases are set on, so a subdivided model keeps a sharp rim, a crisp panel line or a hard corner where you want one.

Edges are picked on the base level (Level 1), the cage the higher levels are made from. A quad's diagonal is no edge: only the polygons' own sides are selected.

Edges mode#

Click Edges mode (the button again, or picking any brush, goes back to sculpting). A Part with subdivision levels steps down to Level 1 first; stepping up again with D pauses the clicks until you are back on the base.

On the model	Does
Click	Select the edge under the cursor (only that one). The edge a click would take lights up as you move.
`Shift`+click	Add the edge.
`Ctrl`+click	Remove the edge (it lights up red).
Double-click	Select the edge loop through it: across the quads, on through every vertex with four edges, until it comes back round or meets a pole or a border. On an open border it follows the border. `Shift` / `Ctrl` add or remove the loop.
Click the background, `Alt`, right-drag	Navigate as usual.

Selected edges are drawn in orange over the model, on the side facing you.

Select by Angle#

Select by Angle selects every edge where the faces on either side meet at more than Angle degrees (30 by default; 0 is flat): the hard edges of a box, the rim of a cut, the ridge of a blade. Lower the angle to find softer edges too.

With Only within selection it keeps just the sharp edges among those selected now: double-click a loop, then Select by Angle to keep only its hard stretch.

Grow, Shrink and the rest#

Grow adds every edge touching a selected one.
Shrink drops the edges at the loose ends of the selection, so it takes back what Grow added to a loop; a closed loop keeps every edge.
Open Edges adds the open (border) edges: the rims of holes and of open surfaces.
Invert swaps selected and unselected edges; Deselect All clears the selection.

The line under the buttons counts the selection (and the creased edges): 12 edges selected of 1920.

The selection belongs to the active Part. Picking another Part, or changing the mesh's polygons (remeshing, Dynamic topology, Remove Hidden), drops it. It isn't part of undo, and it stays when you leave Edges mode.

Creases#

Crease gives the selected edges a crease of the Crease value: 1 is fully sharp, lower values are softer (0.5 is half as sharp). Uncrease removes it. Each is one undo step.

Creased edges are drawn in blue over the base level, brighter and thicker the sharper they are, also when you are sculpting (not in Edges mode); selected creased edges are a thicker orange line. The line under the buttons counts them: 24 edges selected of 48, 24 creased.

Creases are saved in the project with the base level and stay there while you step up and down the levels.

What a crease does to subdivision#

Add Level keeps creased edges sharp (semi-sharp creases, the rules film and game tools share):

A crease of 1 is fully sharp on every level: a creased edge stays a straight hard line, a vertex where two creased edges meet follows the crease, and one where three or more meet stays a hard corner.
Lower values are sharp for fewer levels, then round off: the sharpness is 10 x crease², so 0.5 (sharpness 2.5) is sharp for two levels and half-sharp on the third, 0.25 (sharpness 0.6) only tightens the rounding a little.
A single creased edge ending in smooth surface fades out there: its ends stay smooth.
Open (border) edges were always kept sharp; they still are.

Creasing or uncreasing at Level 1 under existing levels reshapes the levels above when you step up, carrying their sculpted detail along. With no creases subdivision is exactly what it was.

Exporting creases#

File > Export USD / USDZ writes the creases of the level you export: each creased edge as a two-point crease (creaseIndices, creaseLengths, creaseSharpnesses, with the same sharpness, 10 = sharp on every level), and sets subdivisionScheme to Catmull-Clark (Loop for a mesh of triangles), so other apps subdivide the cage the same way. Exporting a higher level writes what is left of the creases on its edges; the top level has none. A plain mesh without creases is written as before (none). Opening a USD file reads its creases back onto the base, in chains or one edge at a time, from any app.

glTF, OBJ, FBX, PLY and STL have no creases: export Level 1 to USD to keep them, or add levels first to bake them into the shape.

Big meshes#

Only the base level is ever searched: the levels above it never pay for edge lists. On a base of a million vertices (two million edges) the edges are found once, in about a fifth of a second, when Edges mode starts; clicks and double-click loops are instant (under a millisecond), and Select by Angle takes under a tenth of a second.

Scripting#

Every click and button runs the edge_select command, so the console and macros show it:

edge_select op=angle degrees=30
edge_select op=loop a=12 b=13 add=true
edge_select op=grow
edge_select op=info

op is edge, loop, angle, open, grow, shrink, all, none, invert or info. edge and loop take an edge index (edge=N) or the two vertices it joins (a= b=).

Creases are the edge_crease command:

edge_crease value=1
edge_crease value=0.5
edge_crease clear=true
edge_crease clear=true all=true
edge_crease info=true

value (0..1, default 1) is set on the selected edges; clear removes their crease; all works on every creased edge of the Part instead of the selection.