PolyPen is a best-in-class topology editing tool, part of the modeling toolset Modeler for Houdini.

No selection, no mode switching, no menus. Hover over a point, edge or face, and PolyPen knows what you're working with. From there, mouse gestures and modifiers do the rest.

One modal tool replaces around 20 operations: moving, loops, cuts, slides, dissolves, bridges, hole filling, extrusion, edge flow, curve editing and full retopology on top of a sculpt.

What's inside:
* Tweak with soft radius
* Edge Flow: Restoring surface curvature
* Insert Loop that follows the profile of the nearer side
* Partial Loop: select part of a ring, then cut it
* Cut that can snap to perpendicular
* Point, edge and loop slide with auto merging
* Dissolve and Delete with cleanup of leftover points
* Edge Collapse and Target Weld
* Extrude in several modes, Inset, Bridge
* Fill Hole: n-gon, fan to the center, or quad grid
* Curves: joining, inserting points, hard corners
* Its own symmetry
* Retopology: everything snaps to the high poly, and the low poly is drawn on top of the sculpt