Properties of Perspective projections - Transformation

1) Faraway objects seem smaller.

2) Straight lines are projected to straight lines.

3) Let line 1 and 2 is two straight lines parallel to each other. The projections of l1 and l2 i.e. also line'1 and l'2 will also be parallel to each other, if line 1 and l2 are also parallel to the plane of projection.

4) If l1 and l2 be two direct lines parallel to each other, although are not parallel to the plane of projection, then the projections of line1 and l2 i.e. also l'1 and l'2, will meet in the plane of  projection as in the Figure 16.

The infinite lines AB and PQ will be projected to the lines A'B' and P'Q' correspondingly upon the plane of projection. There is all points of the line AB is projected to all points of the line A'B'. As the same all points of the line PQ is projected to all points of the line P'Q'. Although A'B' and P'Q' intersect at M and M is the projection of several point on the line AB and also on PQ, but AB¦ PQ, that implies as M is the projection of point at infinity whether AB and PQ meet. In this case M is termed as a Vanishing point.