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Computer Science 184 - Fall 1994 - Barsky - Midterm 1

# Computer Science 184 - Fall 1994 - Barsky - Midterm 1 - CS...

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CS 184 Midterm (Fall 94) UNIVERSITY OF CALIFORNIA College of Engineering Department of Electrical Engineering and Computer Sciences Computer Science Division Computer Science 184 - Foundations of Computer Graphics Fall 1994 - Midterm Exam Professor Brian A Barksy TAs: Dan Garcia and Zijiang Yang Relax. You have 80 minutes. You will be graded on the best 4 out of 5 problems. This means you should allocate about 16 minutes per question. Remember to pace yourself. Feel free to use the back of each page for additional answer space. Do not panic. You will have time. GOOD SKILL Page 1 Question 1: Scan Conversion [25 points] In the figure to the right, the grey area represents a dense concentration of edges of a very degenerate polygon. You cannot tell how many edges there are within that region, nor the direction of them. There are two edges we are sure of - these are labeled in bold with the directions specified. There are two topologically distinct regions we care about, X and Y. Each of A-D is worth 3 points for a correct answer, -1 point for a wrong answer, and 0 points if left blank. This is so that a random guessing strategy will, on average, yield 0 overall points. In the future, this will be written [3/-1 points] to indicate the value of a correct/incorrect answer, and will be used for multiple-choice questions. A) For the Odd/Even rule, is X : (circle one) IN OUT depends-what's-in-the- grey-region B) For the Non-Zero- Winding rule, is X : (circle one) IN OUT depends-what's-in-the- grey-region C) For the Odd/Even rule, is Y : (circle one) IN OUT depends-what's-in-the- grey-region file:///C|/Documents%20and%20Settings/Jason%20Raft...-%20Fall%201994%20-%20Barsky%20-%20Midterm%201.htm (1 of 8)1/27/2007 5:24:08 PM

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CS 184 Midterm (Fall 94) D) For the Non-Zero- Winding rule, is Y : (circle one) IN OUT depends-what's-in-the- grey-region Questions E-G concern rotational invariance (i.e. does the category in question remain constant after an arbitrary rotation) E) Is region classification (i.e. whether a region is in or out) by the Non-Zero-Winding rule rotationally invariant ? [3/-1 points] (circle one) Yes No Depends on ___________________________ F) We specify the color (R,G,B) for every corner of a polygon (as in one of you assignments). We are then given an ideal system in which each pixel is infinitely small (thus we don't have to worry about all of the nitpicky details that arise due to corners falling between scanlines like special cases for convex corners, incrementing the attributes by that additional wierd factor when first added to the edge_y_start list, etc.). We then color the inside of the polygon using a linear interpolation ("lerping") strategy exactly as in your handout. Think very carefully of different types of polygons and the colors that could be chosen when you answer this question. Is the color inside the polygon rotationally invariant ? ("Yes" mean that EVERY polygon's color is rotationally invariant, regardless of the colors and type/size of the polygon, "No" means that NO polygon's color is rotationally invariant, regardless of the colors and type/size of polygon)[6/-2 points] (circle one) Yes No Depends on ___________________________ G) Why ? (provide a sketch if it helps)[4 points]
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