Create a four-sided surface with continuity (Square)
Square creates a four-sided surface by filling a region defined by four intersecting boundary curves. The resulting surface can maintain continuity with surrounding surfaces depending on the options that you set. You can use a curve, isoparm, surface edge, or curve-on-surface as curve types for the square surface boundaries.
In order for a square surface to be created, the following conditions must exist:
The first curve you select sets the U direction for the surface and the second curve sets the V direction.
Click the indicator on a side to set the requested continuity, or open the channel box and set the square surface’s continuityTypeN attribute (the numbers indicate the order you clicked the curves).
Maya will still attempt to create a surface even if it cannot achieve the requested continuity options.
Troubleshooting square surfaces
If a square surface fails to be created as you expect, you should check the following:
You can ensure the curves intersect by either snapping their end points to a common grid line, or by magnet snapping the end point of one curve to the end point of another.
For example, you cannot create a surface inside boundary curves with sharp corners, CV multiplicity, or multi-knots. A boundary curve should also not intersect with itself.
You should ensure that the curves are shift-selected in either a clockwise or counter-clockwise direction. A drag selection, where you define a bounding box around the curves, will not work.
Specifically check that the general Settings positional and tangential preferences are not set at a much larger value than your Square tolerance. If this is the case, Square may not be able to achieve the positional and tangency conditions specified.