ECS175: Computer Graphics
Practice Midterm
Please write your answers ON THESE SHEETS. Attach extra sheets if necessary. The size
of the space indicates roughly the size of the answer we are expecting.
1. (3 points) True or false: An affine transformation of two perpendicular vectors might
produce two vectors which are not perpendicular. Explain your answer with a calcu-
lation or one or two sentences.
2. (3 points) Consider the following matrix product:
200
020
001
0.866 −0.5 0
0.5 0.866 0
0 0 1
a) Describe this transformation as a sequence of motions of the ”turtle”, or graphics
cursor, within its local coordinate system.
b) Describe the transformation as a sequence of operations in the global coordinate
system of an outside observer.
3. (6 points) Describe, using two or three words (eg. dark grayish blue, hot pink), the
color produced by each of the OpenGL commands below.
a) glColor3f(.9, .9, .5);
b) glColor3f(.3, 0, .3);
c) glColor3f(.5, .5, .5);
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