The relative point  

The relative point is a very useful parametric object with great potential to be used in many situations, hence it deserves a detailed explanation.

10 different methods are available to create a point :

- From X, Y and Z coordinates - Curvilinear Abscissa on a curve. - Intersection of 2 curves. - Intersection between a curve and a surface. - Point projection on a surface. - Relative Point - Point On A Vertex - Point On An Edge - Point On A Face   - Relative Point XYZ

The sixth method addresses the construction of a Relative Point. The simplest method is to use the RHINO command and to create a series of points using the "ortho" mode. In this case, if the second point is positioned along the X, Y or Z principal directions relative to the first point, RhinoParametrics will create a relative point (a reference, a direction and a distance).

In the example to the left, Point 8 is positionned relative to Point.5, initially in the X direction. By editing it, direction, sign and distance can be changed, and once can even add an offset rotation angle. Dimensions and offsets can also be directly modified in the display window.

All RHINO commands creating a series of points can also automaticaly create their dimension as polylines or rectangles.

In the example to the left, a series of line segments has been created. All points, except for the first one, are relative points. The second point is edited to add an angle, and then the dimension of the third and fourth point are modifed. The line segments are obviously updated following the modified dimension.

Finally, if the first point is moved, the complete series of points is modified. Note that the dhe dynamicaly built rectangle also uses relative points.