To accurately aid positioning when interactively manipulating entities with respect to the representation of other an object snapping feature is available. Two types of snapping are supported, Control point snapping and Curve snapping.
Control Point Snapping
Control point snapping allows a control point to be position in exactly the same position as a control point from any entity in the environment. This can be useful when trying to the definition match a NURBS type entity with another, for example, trying to match the edges of two B-Spline Surfaces. When a position for control point snapping has been found, a thick square icon will be displayed around the selected control point.
Curve snapping allows a control points to be accurately positioned on a curve entity's representation by locating the position closest to the manipulated control point. This is useful when defining CAD type modes using Polylines, Circles or Arcs. When a position on a curve has been found, a thick cross icon will be displayed at the selected location.
If both a control point and curve snap locations are available, the control point will take priority over the curve snap. The color of snap icons is defined in PolyCAD Options Panel -> Colors using the Snap Color parameter. Object snapping does not form a persistent relationship between the two entities. Consequently, if the snapped to entity is manipulated, the other entity will not update. Entities which are parametric in nature may not support the Snap to Grid option if it is likely to cause undesirable behaviour during interactive manipulation.
If a curve is defined on a plane (IntellCurves, X-Topology Curves) then control points will snap to locations defined by the intersection of the plane and the neighbouring curves.
Controlling Entity Snapping
The entities to which you can snap to is controlled from the status bar by right-clicking on OSNAP. In addition, snapping can be turned on and off by double clicking on the OSNAP text.