Projections:

To view a 3-D model it is essential to have 3-D display devices. Though, mismatch between 3-D models and 2-D screens may be resolved by utilizing projections for transforming 3-D models onto a 2-D projection plane.

There are two kinds of projections. One is planar geometric projections wherein straight lines are maintained and the viewing surface is also plane. The other is non-planar geometric projection wherein both projector and the surface are curved. In this section, we are going to discuss the first type of projections that is Planar Geometric Projections.

To describe this, a centre of projection and a projection plane should be defined. To obtain the projection of an entity, projection rays (called as projectors) are constructed by linking the centre of projection with each point of the entity. The intersections of these projectors along the projection plane describe the projected points which are linked to produce the projected entity.

Perspective projection makes an artistic effect that adds some realism to perspective views. In this case, size of any entity is inversely proportional to its distance from the centre of projection.