CS 426 Exercises
Write the radiosity equation. For each of the terms (B, E, rho, and F)
describe its meaning and give suitable units.
The radiosity equation is system of equations. What are the
variables to be solved for? Is the system of equations linear?
Which of the following assumptions must be true for the basic
radiosity equation to be a good approximation to the rendering
equation: a) all surfaces are diffuse, b) all surfaces are
planar, c) the radiosity is the same at all points on a patch
element, d) there are no occlusions resulting from one patch
blocking light transfers between any other two patches.
If we write the radiosity equation as Ax=b, consider the
properties of A: What are the values on the diagonal for planar
patch elements? Is the matrix diagonal dominant? Is it symmetric?
When can it be singular? Is it positive definite?
The radiosity method studied in class simulates which types of
lighting effects: a) shadows, b) direct illumination from area
light sources, c) direct illumination from point light sources,
d) indirect illumination due to reflections off specular surfaces,
e) indirect illumination due to reflections off diffuse surfaces?
Write an an expression for the form factor F_ij for two mutually
visible patch elements i and j. Give a short intuitive explanation
for each term. How does the expression change if the two patch
elements are partially occluded by blockers?
What is the relationship between F_ij and F_ji if we assume
uniform light reflection?
What is radiance? How is it different than radiosity?
Is the progressive radiosity method assymptotically more
efficient than Gauss-Seidel iteration? If so, why? If not,
why do people use progressive refinement?