Past Midterm and Exam Questions (PDF) - Student.cs.uwaterloo.ca ...

CS488/688 Introduction to Computer Graphics 5
2.2 Super- and Stocastic-Sampling [Last Used: Winter 1996]
Super-sampling and stocastic sampling are two methods for anti-aliasing.
1. Describe both methods.
2. With both techniques, we are still taking a discrete sampling of a continuous signal.
Describe why/how each method reduces aliasing artifacts.
2.3 Aliasing and Anti-aliasing [Last Used: Fall 2012 Final]
• Describe 3 aliasing artifacts present in Computer Graphics.
• Describe one method of anti-aliasing.
2.4 Aliasing [Last Used: Winter 2000 Final]
Suppose we wish to rasterize two triangles T1 and T2 given screen space coordinates for their
vertices as indicated in the diagram below.
10
5
(3,5)
T1
(11,6)
1
1
5
T2
10 15
a) If both triangles are black on a white background, a naive approach would be to fill in each
pixel that contains any piece of either triangle. What is the common name for the aliasing
effect that would result?
b) A triangle strip, often used to quickly render surfaces, is a sequence of triangles joined at
shared edges. What is inefficient about rasterizing a triangle strip by filling the triangles
one-at-a-time using the method in (a)?
c) Suppose T1 has RGB colour (16,16,16), T2 has RGB colour (0,0,16) and the background has
RGB colour (0,0,0). If the rasterization was antialiased using the obvious approach, what
colour should pixel (3,5) be shaded? What colour should pixel (11,6) be shaded?
d) Analytic antialiasing is difficult in ray tracing. Name an alternative approach and two possible
variations.