•
Parallel projections:
–
no
shortening due to distance
–
several
kinds, depending on orientation:
•
isometric,
cavalier,…
•
Perspective projections:
–
shortening
of objects in the distance
–
several
kind, depending on orientation:
•
one,
two, three vanishing points
Parallel
Projection Matrix
•
Parallel
projection onto z=0 plane:
x’=x,
y’=y, w’=w
Matrix
for this projection:
Perspective
Projection Matrix
Projection
onto plane z=0, with center of projection at z=-d:
Perspective
projections pros and cons:
Size varies inversely with distance - looks
realistic – Distance and angles are not (in general) preserved – Parallel lines
do not (in general) remain parallel
Parallel projection pros and
cons:
Less realistic looking + Good for exact
measurements + Parallel lines remain parallel – Angles not (in general)
preserved
