Pelting

The UV Pelt operator gives you a streamlined workflow for unwrapping UVs on organic characters. UVPelt operates similarly to how a tanner creates a pelt. You make cuts to the geometry to produce a surface topologically equivalent to a disc. Houdini connects the boundaries of this surface to a frame shape and stretches it out. The result is a great starting point for setting up character UVs.

The basic pelting workflow involves establishing cut lines and the center polygon from which the UVs will be stretched. More advanced techniques include the ability to adjust the spring tension on surface points to loosen up the UVs in certain areas, and to choose a custom pelting frame which provides an alternate boundary for stretching the UVs.

In the viewer pane, use the tab menu to choose the UV Pelt operator.

Select edges along which the UVs should open up. To do this quickly, select a single edge in the line you want and use the L key to grow the selection along the entire line of edges.

Click CtrlLMB on the "center" face which the pelt will stretch outward from.

Click RMB to finish the selection.

You can select a closed curve to use as the stretching frame. To simply use the default circle frame, click RMB without selecting anything.

In the UV texture editor viewport, the UVs should be unwrapped.

Use the Pelt node's and parameters to control the amount of stretching.

You can optionally paint a tension attribute on the surface to control the amount of stretching, where lower values (less than 1) mean more stretching. See the painting spring tension example.

You can also optionally paint a density attribute on the frame curve (if you use one) which controls the amount of pull along the length of the frame curve. See the pelting frame example.