CMSC 435 Autumn 1997 --- Introduction to Interactive Graphics
Smooth Shading vs. Faceted Shading
Faceted Shading:
- 1 color per polygon
- produces "unsmooth" objects
- direct rendering of the geometry
- fast
Smooth Shading:
- assumes object is really a curved surface,
approximated by a collection of polygons.
- more realistic rendering
- slower
- Two Types: Gouraud and Phong
Gouraud Smooth Shading (1971):
- Calculate Average vertex normal
- Perform illumination calculation to get vertex
colors
- Interpolate vertex colors accross the face.
- Suffers from Mach banding :
Whenever the slope of the light intensity curve changes
abruptly,
the surface appears brighter (inflection is
concave) or darker (convex)
- May miss highlights within a face.
Phong Smooth Shading (1973):
- Calculate Average vertex normal
- Interpolate vertex normals accross the face.
- Perform illumination calculation at each pixel
- More accurate highlights
- Fewer Mach Band effects
- Why do they occur?
Comparison of Shading Types
David S. Ebert
Sun Nov 16 11:19:09 EST 1997