By default, drawing will occur on the current working plane which is the plane aligned with the global axes, that is most normal to the current viewing direction and passing through the current drawing depth.  To help with the alignment of the model and to allow drawing out of the current working plane Multiframe uses dynamic line constraints.  When drawing a member, if the cursor has snapped to a joint and the mouse moved in the direction of one of the global axis, drawing will be constrained to occur along this direction in 3D space.

The constraint of drawing to the global axis direction described above is in fact part of a more general concept for automatically constraining the direction the mouse moves in 3D space.  The drawing direction can also be constrained to occur in the direction of members connected to a joint. If the mouse is moved in the direction of a member attached to the joint then drawing will be constrained to the direction of that member in 3D space.

When movement is constrained the direction of a global axis or element, a small arrow will be drawn at the cursor pointing in the direction of the line of the constraint. The colour of the arrow indicates is the constraint is in the direction of a global axis or a member.

The drawing constraint will be deactivated if the cursor is moved to far away from the direction of the constraint. This can be avoided by holding down the shift key and this will force the current restraint to remain active.

Dynamic line constrains can be disabled via the new Drawing Settings dialog.