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TEST 3 - CS458 
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Instructor Dr P Juell                   NAME_______________________ 
OPEN BOOK                                        Dec 2, 1998
100 points         
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1. (24)
Virtual Reality (VR) worlds allow walk through or fly through interaction
with the image.  
This means the view point and camera angles can quickly change.  
Assume the starting image has been calculated.  How much work will it
be to compute the next viewing location?
Some techniques will not have to recompute everything as the viewpoint
changes. These techniques then would be faster for VR models.
Identify the following algorithms as L (low re-computational requirements),
H (high re-computational requirements), or M (Moderate re-calculations required
but not large scale calculations).
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___ ray tracing
___ radiosity 
___ flat surface lighting with only ambient light
___ Gouraud shading (without specular highlights
___ Phong shading  (without specular highlights)
___ Phong shading with specular highlights
___ depth-buffer visible surface (z-buffer)
___ scan-line visible surface
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2. (10)
Pick a technique presented since the last test. 
Name the technique.

Give an example (probably a diagram) where this technique produces a
wrong answer.
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3. (10)
Give an example where you would want to use dithering.
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4. (10)
You are given a list of exponents for the Phong specular highlight
formula and a list of surfaces.  Match the values and surfaces so
the list makes reasonable sense.  

Exponent values: 1, 50, 100 150, 200

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____ mirror
____ skin (human)
____ sand paper
____ coins
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5. (6) 
What does a dot product of 0 mean in doing a back face removal algorithm?
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6. (20)
Draw a diagram and label it for a surface, a light source and a viewer.
Then give the full formula for the light reaching the viewer.
Remember to include the ambient, diffuse and specular components.
(Ia ambient, Ii illumination light from the light source )