Viewer2d sample demonstrates how the functionality of TKV3d package can be
used for 2D visualization. It provides samples of 2D objects visualization,
dynamic selection and highlighting.
It illustrates how to:
1) implement 2D view behavior with V3d_View class, with interactive zooming
and panning of the 2D scene;
2) draw 2D primitives like rectangles, lines, curves;
3) draw different types of markers;
4) draw text defined by its font, height, style, angle;
5) display 2D curves of a face' edges and group them using orientation 
criterion;
6) display zoomable images;
6) display circular and rectangular grids .

Viewer2d support zooming ,panning of displayed objects and
circular and rectangular grids. 