Sharp / Curvy mini tutorial.
sharp here but curvy there

This is a very quick and dirty tutorial that explain the good and the wrong way to create mixed sharp/smooth shapes with sPatch.

the WRONG way ... very inefficient!
smooth profile extruded along sharp path YOU LOSE!
The wrong way consist in trying to extrude  a curvy profile. The result of this operation is a totally curvy shape. If you try to use the peak  or round  tool on a selection of points to sharpen the angles, you fail every time because sPatch will not let you modify both direction independently this way. 

To modify the u and v directions of a knot independently, you must select each edge using TAB key when one knot is selected then modify that edge. So, it is POSSIBLE to get the wanted shape this way but you are going to waste a lot of time smoothing edges independently. :-(
the RIGHT way :-)
sharp profile extrude once then twice untill it's nice :-)
 

The proper way to generate such a mixed sharp/curvy shape is to start with the sharp profile and to use the extrude tool  as many times as needed along the wanted curve. extruded profiles can also be rotated  and tranlated  to obtain the curvy path with modifying the smoothness/sharpness.

This approach is garanteed to work because sPatch generates smooth curves by default when extruding but doesn't modify the smoothness of the profile prior to that.

 shaded shape

NEWS: When first published this tutorial stupidly stated that sPatch did not allow independant modification of curves in u and v directions. Only one day after publishing Mike Clifton wrote:

"Performing the peaking/smoothing before extruding is probably the most effective way to create those shapes, but you're wrong that sPatch can't smooth the u and v directions independently. I won't flame you though, because I probably either didn't document this, or didn't make it clear.

How it works is like this: when you select a point and hit the peaking/smoothing tool, by default it affects all the curves passing through that point. To work on only one curve, select the point, then press repeatedly until the curve you want to peak (or smooth) becomes highlighted. Then hit the peak/smooth button. Hitting only works when one point is selected, so to use this feature, you have to peak/smooth the points one at a time, so it's kind of a pain, but it is possible to do."

So here you go! I had a sneaky feeling about this and how stupid of me not to have thought of that :-o I guess I'll email him first before I say things like that next time ;-) Well thanks mike, I'm quite happy to be wrong about this one .. it opens a whole new range of creative possibilities.