TITLE: Construction Plane Editing
TYPE: Generic State

The construction plane editing operation allows for interactive manipulation
of the construction plane.

Left-mouse anywhere on the construction plane and drag to move it along its
plane.  Right-mouse anywhere on the construction plane and drag to build a 
construction plane that is perpendicular to the current one. Hold down Ctrl
while dragging if you want to align the new plane to the axes of the original.

Ctrl-right-mouse will present a menu that allows you to control many parameters
of the construction plane, including control over the construction-plane 
elevation, alignment, size and position.

Clicking the mouse outside the construction plane allows you to orient it 
with other geometry.  Click-orienting can be achieved in the following ways:

 - Left-click on a single point outside the construction plane and then 
   right-click to move its origin to that point.

 - Left-click on two points and right-click to align the edge of the 
   construction plane with the two points.

 - Left-click on a single point and a normal, on three points, or on an edge
   and a point to align the construction plane with the plane specified by the 
   selection.

 - Left-click on a normal to align the construction plane's normal to the 
   selected normal without moving the construction plane.

 - Alt-left-click on an edge to align construction plane's normal to that edge.

Do all of the above clicking with the middle mouse to orient the so-called "up
vector", which determines the axis along which to translate geometry when
the Alt modifier is held down in operations such as Transform and Edit. By
default, the height vector coincides with the plane normal and can be brought
back to its default using the Ctrl-right-mouse menu.

The construction plane handle that is available from the right-mouse menu of the
construction plane button below the viewport provides much of this functionality
without having to enter the construction plane operation. 

Right-mouse over the construction plane any time during a houdini session to
bring up the construction plane menu regardless of what operation is current.
