1. CSL 859: Advanced Computer Graphics
Dept of Computer Sc. & Engg.
IIT Delhi

2. Graphics Pipeline Transform vertices Light vertices
Clip to Window extremes
Setup edges
Rasterize
Fill and interpolate colors, depth
Test against Z-buffer
One entry per pixel: closest so far
Update Color and Z buffers

3. Light Vertices Color Light Direction normal Point Directional Or Both
View Direction

4. Lighting in which space?+1 -1
z=1
Near Plane
Far Plane
Projective?
Distances get distorted
Clip coordinates
Normalized device coordinates
Screen?
World
Camera -1

5. Homogeneous Space Clipping
Clip coordinates = projective coordinates
-1 < x/z < +1 (after perspective divide)
-1 < x/w < +1 (clip)
-w < x < w
-w < y < w
0 < z < w

6. Rasterize x0,y0,z0 y = mx + c x = 1/m(y+c) =ay+b x2,y2,z2
x+1 = ay+a + b
= x + a
zp-zl xp-xl
zr-zl xr-xl =
x1, y1,z1
zp+1 = zp + k

7. Perspective Distortionz2 z1

8. Perspective Distortion

10. Perspective Correction
Linear interpolation:
p(t) = p1 + (p2 – p1) t, 0 <= t <= 1
Screen space interpolation:
ys = y1s + t (y2s – y1s)
y/z = y1/z1 + t (y2/z2 – y1/z1)
But also:
y = y1 + u (y2 – y1)
z = z1 + u (z2 – z1)

11. Perspective Correction

12. Perspective Correction

13. Perspective Correct Z

14. Perspective Corrected