I've marked the midterms and posted the grades on WebCT. Hopefully you will receive your papers back in class tomorrow (Oct 27).

Here is how I broke down the marks for most questions (some
of the 5 mark questions aren’t listed because they are more straightforward).

If you think your answer deserves more marks or that I
missed something in determining the correctness of your answer, send an email
that demonstrates this. If indeed I
think you deserve more marks, I’ll ask you to bring in your midterm paper.

Be sure to check my addition!

**Number 1**

·
2 for the projection role

·
2.5 for the defining parameters (0.5 each)

·
2.5 for the diagram

·
1 for what defining parameters form

·
2 for implication on visualizing game objects

**Number 2**

·
4 for explaining what homogeneous coordinates
are

o
3 if correct but not quite enough detail

·
4 for explaining the motivation for them

·
2 for giving example of where they are used

o
1 if you give a correct example but offer an
incorrect reason

**Number 3**

·
For general matrices, 1.5 each for the two
translation matrices and 2 for the rotation

·
5 marks for the second part: 1 mark for each of
four matrices (including the point) and 1 one mark for the correct order

**Number 4**

·
15 for describing the steps properly

o
4 for defining two vectors using the triangle
points

o
3 for finding the normal via the cross product
of these two vectors

o
4 for defining a vector from the triangle to the
viewpoint

o
4 for computing the cosine of the angle between
normal and vector to the viewpoint (only the sign matters)

·
5 for drawing an accurate picture

o
2.5 if the overall idea is there but it does not
generalize well and/or does not show U, V, W, P, or other parts of the
computation in the first part

o
2 if the diagram is good but based on wrong
method

·
5 for correctly computing whether T is visible
from P

**Number 5**

·
5 for saying why the transformation computes
Z-values

o
1 if you mention removing shapes outside view
frustum (this will happen before the projection transformation)

·
10 for correct computation

o
7 if correct but not enough math shown to show
full understanding

o
9 if there’s a small error

o
7 if you don’t properly multiply the homogeneous
coordinate of the point with the value in position (4,3) in the matrix to end
up getting zero in the result

**Number 6**

·
5 for computing orientation

·
7 for computing avatar position

o
5 if you don’t show enough math

o
4 if you don’t normalize the orientation vector
and multiply that by 50 units

·
8 for
avatar’s position and orientation

o
7 if you did not do the math and/or there are
small errors

o
4 if the method is wrong

**Number 8**

·
2.5/5 for saying the objects occupy the same
space and to pick just one (without saying how)

·
3.5/5 for saying the objects occupy the same
space and to change their z-value

**Number 9**

·
3/5 for saying the object is outside the “render
distance”

**Number 10**

·
3 for explaining the purpose

·
2 for the example

o
1.5 if example is good but based on incorrect
understanding of part 1