Angel and Shreiner: Interactive Computer Graphics, Seventh
Edition
Chapter 7 Odd Solutions
7.1 The major problem is that the environment map is computed without
the object in the scene. Thus, all global lighting calculations of which it
should be a part are incorrect. These errors can be most noticeable if there
7.3 Consider a single sine wave that is sampled at a rate just over the
Nyquist rate with the first sample where the sine is zero. The next sample
will be slightly greater than zero, the following slightly greater (in
magnitude) than the second, and so until we get samples about equal to
7.5 Once aliasing occurs, it is very difficult to remove because the data
that has been aliased at another frequency is mixed with any unaliased
data at that frequency. Thus, if we remove energy at that frequency, we
7.7 The basic problem is that when we use subtractive colors and filters,
1
the colors modulate each other and there is a multiplicative rather than
additive relationship. Thus, if we have two CMY colors. (C1, M1, Y1) and
7.11 Suppose that the histogram of the image is a function f(x) where xis
the luminance. The lookup table formed from the function Rx
0g(x′)dx′will
create an image with a flat histogram. A simple discrete example is
illustrative. Suppose we have a image which is 1024 x 1024 and has 256
7.13 In the perspective projection, each row of squares will have a different
size and thus each will appear as a pattern with a different frequency.
Consequently, there will be different Moire patterns. In a parallel
projection, once the checkerboard is oriented, the patterns are all the same.
7 .23 Generally back-to-front rendering is nice because faces in front
always paint over surfaces behind them. However, the final color is not
determined until the front most object is processed. Suppose you have a
7.27 Each time a new mipmap is created, we need 1/4 of the storage of the
2
3