21	Horowitz, Marc		marc		6-3	3	y
	no checklist, erik kay graded and said it was aok
 	1. 24	You step through x and y in the world and hope
		that this will set every value in the image. However,
		due to perspective projection, this is not always guaranteed.
		Instead, you should be stepping through the image and
		determining the intersection with the sphere. This was
		shown in class...
		In addition, your view and light vectors are dependent
		on the surface point. We asked you to make the infinite
		viewer/lightsource approximation so that shading can
		be discriminated.
	2. 40	What's the purpose of dividing the color by 3 (ConstPlot.C)
	3. 30
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