Im almost certain it should be as straight forwards as selecting a closed curve like in this image, and choosing close curve or create surface from curve???
Ummm NO it's not!
1st when you said created a "cap" did you mean a "planar" surface? If so that is why it disappears. A planar cap is just what its name implies - it's planar. As soon as you move a vert off plan the surface will become invalid.
This step would be very simpe in 3d Max, but how is this done in Maya please?
Really? Please demonstrate for us.
As far as I know there is NO modeling application, even 3d max where it's as simple as selecting a closed curve and say make a non-planar surface cap! A simple closed curve that is not planar does not have sufficient information to define a surface that encloses it!
Take the image you provided as proof. Start with the non-planar curve now just draw a series of edges vertically from edge to edge left to right and imagine lofting a surface between the edges.
Now take the same starting curve and draw a series of edges this time horizontally from edge to edge top to bottom of the closed curve and loft those.
You will see that you get two completely different surfaces and second you will get a surface that is all messed up because drawing straight edges only creates a proper surface if the closed curve is PLANAR.
You can repeat the exercise drawing straight edges for an infinite number of angles and unless the curve you are filling in is planar the surface created will be a mess. The software has insufficient information to compute the proper contours to cap a non-planar closed curve.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675
Last edited by ctbram; 03-12-2013 at 10:59 PM.