Computer Science 455 Instructor: R. P. Burton Third Quiz October 21-22, 2002 Name _________________________________________ Score ____________/29 1.____ polygon clipped using Sutherland-Hodgman clipping produces correct results. a.Any b.A convex c.A concave d.Neither a convex nor a concave (b) 2.A polygon to be clipped using Sutherland-Hodgman consists of 8 vertices. How many vertices does the resulting polygon have? a.8 b.possibly more than 8, but the vertices beyond 8 will be coincident c.not more than 8, and usually less d.just can’t say (d) 3.____ polygon clipped using Wiler-Atherton clipping produces correct results. a.Any b.A convex c.A concave d.Neither a convex nor a concave (a) 4.For “all or nothing” string clipping, it is sufficient to test two diagonally opposite corners of the box which encloses the string tightly. a.true b.false, unless the corners are upper left and lower right. (a) 5.Which of the following is/are (a) consideration(s) in choosing which components of a scene constitute a “segment?” a.components that always will be modified “as a group” b.ease of construction c.ease of processing d.(all are considerations) (d) 6.What is the appropriate name for an efficiently constructed segment? a.a short, but descriptive name b.a unique name (relative to all other classes) c.an integer (c) 7.Which of the following is the state most difficult to correct? a.posted and painted b.posted and unpainted c.unposted and painted d.unposted and unpainted e.(all are desirable states) (c) 8.In what coordinate system should symbols be defined? a.master coordinates b.world coordinates c.normalized device coordinates d.physical device coordinates e.(none of the above) (a) 9.Suppose a building complex consists of three department complexes, each of which consists of five office complexes, each of which contains a desk, a chair, and a computer. All of these are entered intelligently into a hierarchy. Suppose the desk has been placed in the fourth office complex in the second department which, of course, is in the building complex. How many matrices need to be concatenated at this point to produce a transformation to put a properly oriented and scaled chair in its place in the office with this desk? a.one b.two c.four, if you don’t worry about mappings to normalized device coordinates, etc. d.more than four (b - the desk’s “transformation” onto the saved office’s transformation) 10.The user dialogue in a GUI should be in the language of a.GUI’s, according to ISO GUI Standard b.the application (b) 11.A mouse is being used as a stroke device. Select the appropriate input mode. a.request b.sample c.event (b) 12.A stylus is being used as s keyboard. Select the appropriate input mode. a.request b.sample c.event (c) 13.A button is clicked at two different locations to determine the endpoints of a horizontal line. With each click, the x and y coordinates of a point are provided. How many individual coordinates need to be used to produce the line? An x-coordinate is an individual coordinate, as is a y-coordinate. a.two b.three c.four (b – the second click provides only the x coordinate, since the y coordinate is determined already) 14.Which of the following produces the least aesthetically pleasing rubber lines? a.copy the contents, draw the line, move the line, replace the contents b.draw the line using XOR mode c.draw the line, move the line, redraw the entire scene (b) 15.Which of the following techniques is least likely to be effective for selecting a part of a picture (such as the fly on the door knob on the door on the wall on the house)? a.place the cursor over the fly and click b.provide a tight bounding box around the fly c.highlight the fly, the door knob, the door, and the wall in succession until the user indicates that the selected object is being highlighted d.put a “handle” on all the candidate objects e.remember that the user just selected the bee on the window, and before that he selected the flea on the dog. f.(all are equivalently likely to be effective) (a) 16.Why are parallel projections considered appropriate? a.because draftsmen used them for years – they represent a tradition which ought not to be discarded lightly b.because they represent the same kinds of images our eyes produce c.because they lend themselves to measurement d.they are not appropriate and, along with neckties, should be abolished (c) 17.Everyone sees darker (or thicker) lines on a line drawing as being closer to the viewer. a.true b.false (b) 18.Which of the following would be most appropriate for providing a description which, when rendered, would be recognized by the viewer as a realistic representation of the Matterhorn (a famous mountain on the Swiss-Italian border)? a.construction methods involving union, intersection, and difference b.a (measured) polygonal approximation c.parametric curves d.fractal techniques e.particle techniques (d) 19.Which of the following would be most appropriate for providing a description which, when rendered, would be recognized by the viewer as a realistic representation of either of the course TAs? a.construction methods involving union, intersection, and difference b.a (measured) polygonal approximation c.parametric curves d.fractal techniques e.particle techniques (b) 20.A general method can be written which accepts the x, y, and z coordinates of three noncoplanar points and returns the planar coefficients A, B, C, and D of the associated plane. a.true b.false (a) 21.Given the coordinates of a point in three-dimensional space and given the equation of a plane (Ax + By + Cz + D = 0), it is possible to determine: a.if the point lies in the plane b.if the point lies “in front of” the plane c.if the point lies “behind” the plane d.(all of the above) (d) 22.Suppose the normals of a large collection of three-sided polygons are computed. Suppose next that the coordinates representing polygon vertices are transformed (translated, scaled, rotated, sheared, and reflected) by some transformation T. What is the most efficient way to determine the new normals? a.nothing is required; the normals do not change b.recompute the normals using the new vertex coordinates c.transform the normals using the same T d.transform the normals using the inverse of T (d) 23.Quadric surfaces include spheres, ellipsoids, tori, paraboloids, hyperboloids, etc. What are superquadrics? a.The four (or higher) dimensional counterparts of the quadrics b.Hybrid quadrics – mixtures of quadric surfaces c.Quadrics with parameters for adjusting their shapes (c) 24.Which of the following are the best examples of blobby objects? a.clouds b.your biceps c.time samples of shaving cream as you spray it into your hand (b) 25.Suppose you have a curve in three-dimensional space determined by the three-second path of a fly inside a large jar on whose inside surface the fly never lands. What is a good choice for the independent variable for specifying the path? a.the x coordinates b.the y coordinates c.the z coordinates d.something else – maybe time e.(all are good choices) (d) 26.Suppose the fly tires and rests briefly on the inner surface of the jar. What sort of continuity exists at this spot in the fly’s overall journey? a.zero-order b.first-order c.second-order d.higher-than-second-order (a) 27.Parametric equations which interpolate control points are always preferable to parametric equations which approximate the same control points. a.true b.false (b) 28.Suppose you have 20 sets of four control points, and 30 sets of five control points. You wish to determine Bezier curves for each of these 50 sets of control points. How many blending functions do you need to determine? a.5 b.9 c.5 x 50 d.(4 x 20) + (5 x 30) (b) 29.How many steps are taken from one end of a Bezier curve to the other end of the same Bezier curve (with a point on the curve being determined at each step)? a.n + 1, where the control points are numbered 0 to n b.(n + 1) x 2, as dictated by the Nyquist frequency requirements c.the same as the magnitude of the axis of greatest excursion d.whatever you please (d)