How to extrude a sharp edge in form tool?

[SdongLAXTX]

I know to press alt to extend a surface in form tool, but i can't figure out how to do like this (start form 00:08)

[tallisb]

Hello-

It looks like the edge that was pulled was "creased".  You can select an edge, right-click and select "Crease".

Also, depending on which Display Mode you are in, it will return different results.  For example, if you are in "Box" Display Mode, it will show curved faces as flat "box" faces.

Hope this helps.

Brad

[SdongLAXTX]

Really appreciate for your help! It's seems like it's extend from an edge! Crease function don't let me select the side but only the inner lines, is there anyway for me to Crease the edge of the plane?

[TrippyLighting]

As one of the more experienced T-Spline modelers on this forum here I would strongly discourage you from modeling with creased edges. If you do need creased edges, then apply them at the very end of the modeling process.

If you need them to better judge a form, apply and then remove them again before continuing to model.

It does not happen often,  but I've seen enough models by users on this forum that were only salvageable by exporting the control cage and re-importing it.  The "Utilities->Make Uniform" tool is supposed to fix such cases, but it doesn't work in every case 😉