Computer Science 455 Instructor: R. P. Burton Fifth Quiz November 7-8, 2005 Name _________________________________________ Score ____________/46 1.What is the minimum dimensionality of a “hider” in 4-dimensional space? a.one b.two c.three d.four (c) 2.Continuing the previous question, all objects of that dimension are “hiders” in 4-dimensional space, independent of their orientations. a.true b.false (b) 3.All the features of 3D computer graphics have commonly-used counterparts in 2D computer graphics. a.true b.false (b) 4.Producing a stereo pair is as simple as slightly displacing the “look from” position while maintaining the “look at” position. a.true b.false (a) 5.Quadrics include spheres, ellipsoids, tori, paraboloids, and hyperboloids. Superquadrics include hyperspheres, hyperellipsoids, hypertori, hyperparaboloids, hyper-hyperboloids, AND other shapes which have no 3D counterparts. a.true b.false (b) 6.Which of the following likely would be modeled as blobby objects: a.a ball of cotton b.your bicep muscle c.dried mud d.(all of the above) (b) 7.Pick the best definition of a parallel projection: a.points are projected to the viewing surface along parallel lines b.points are projected perpendicular to the viewing surface c.points are projected to a common center of projection which lies somewhere between the points and the projection surface d.points are projected to a common center of projection on the opposite side of the projection surface (a) 8.Pick the true statement: a.a projection cannot be both parallel and orthographic b.a projection cannot be both parallel and oblique c.both (a) and (b) are true d.neither (a) nor (b) is true (d) 9.An axonometric projection is a _______ projection (pick the most complete, true answer) a.parallel b.perspective c.parallel orthographic d.parallel oblique e.isometric (c) 10.What is the fundamental difference between a cavalier projection and a cabinet projection? a.one is oblique, the other is orthographic b.one is parallel, the other is perspective c.a scaling in the z direction d.one projects at 45°, the other at 30° (c) 11.A perspective projection involves a.a division of x and y by z b.a division of x and y by sqrt (x2 + y2 + z2) c.a simple dropping of the z coordinate (a) 12.A polyhedron can determine at most ____ vanishing point(s). a.one b.two c.three d.arbitrarily many (d) 13.The viewing transformation is a transformation which maps the ______ onto the _____. a.viewing coordinate frame, world coordinate frame b.world coordinate frame, viewing coordinate frame (a) 14.The viewing transformation is fully determined by specifying a “look at” point and a “look from” point. a.true b.false (b) 15.What is the orientation of the central axis of a view volume relative to the screen? a.always perpendicular b.always parallel c.always oblique d.(none of the above) (d) 16.What is the purpose of near and far planes? a.to take cross sections b.to focus the precision of the machine on the range of interest c.both (a) and (b) d.neither (a) nor (b) (c) 17.Converting a viewing pyramid into a viewing parallelepiped is ______ transformation. a.a shearing b.a scaling c.neither a shearing nor a scaling d.an impossible (b) 18.Where is the center of projection for a parallel projection? a.perhaps 15” from the screen b.far, far away, even beyond Judea’s plains (actually, they are hills) (b) 19.It ____ possible to produce a single 4 x 4 transformation matrix which maps an object from master coordinates all the way to device coordinates, even with perspective projection. a.is b.is not (b) 20.Nicholl Lee Nicholl has a 3D counterpart which we discussed in class and which is presented in the text. a.true b.false (b) 21.For what industrial segment were Bezier curves and B-splines developed? a.flight simulation b.advertising c.vehicle design d.architectural design (c) 22.For a self-intersecting curve (with multiple values of x for a single value of y, for example), the curve should be represented a.with x as a function of y b.with y as a function of x c.part using (a) and part using (b) d.parametrically (d) 23.Second order continuity assures first order continuity which insures zero-order continuity. a.true b.false (a) 24.All things concerned, curves which ______ the control points typically are preferred. a.approximate b.interpolate (a) 25.The parts and pieces of the “formula” for Bezier curves a.each represent something intuitively understandable b.can be derived, but have no obvious intuitive meaning c.cannot be derived by the typical senior in computer science, and have no obvious intuitive meaning (a) 26.What is the “convex hull” property? a.the control points, taken in sequence, describe a convex polygon which fully contains the curve b.a “rubber band,” allowed to collapse onto the control points, describes a convex polygon which fully contains the curve c.the associated Bezier curve is devoid of concavities (b) 27.Bezier curves never close. a.true b.false (b) 28.A particular Bezier curve is described by 7 control points. What is the maximum degree of the associated polynomial? a.6 b.7 c.8 d.unlimited (a) 29.Continuity at the joint of two Bezier curves ______. a.is always zero b.can be controlled (b) 30.Bezier curves exhibit _____ control; B-spline curves exhibit _____ control. a.global, global b.global, local c.local, global d.local, local e.local or global, local f.local, local or global (b) 31.Bezier surfaces _____ the same number of control points in each direction, and ____ require the same number of subdivisions in each direction. a.require, do b.require, do not c.don’t require, do d.don’t require, don’t (d) 32.Two properly spliced Bezier surfaces can exhibit _____ at the splice. (pick the “richest” correct answer) a.not even zero-order continuity b.zero-order continuity c.first-order continuity (c) 33.A triangle is swept translationally over a nonzero distance to produce a highly accurate polygonal description of a triangular prism. How many vertices must be generated? a.3 b.6 c.probably several hundred (b) 34.A polygon can be subjected to all of the following during a sweep EXCEPT a.rotation b.movement along a Bezier curve c.scaling d.shearing e.reflection f.(no exceptions here) (f) 35.“Gluing” is a(n) _____ operation. a.union b.intersection c.difference d.complement (a) 36.Produce a sculpture from a plaster cast is a ____ operation. a.union b.intersection c.difference d.complement (d) 37.Drilling is a(n) _____ operation. a.union b.intersection c.difference d.complement (c) 38.Stereolithography is a(n) _____ operation a.union b.intersection c.difference d.complement (b) 39.Which of the following techniques would be most suitable for rendering the intersection of two 3D shapes? a.sweeping b.octrees c.ray casting (c) 40.The storage requirements for information stored in an octree are typically _____ order(s) of magnitude greater than the storage requirements for storing the information as a collection of polyhedral shells. a.no b.one c.two or more (c) 41.Most of the hidden-element removal algorithms discussed in class were _____-space algorithms. a.image b.object (a) 42.Back-face removal removes approximately ____ of the polygons in a scene. a.10% b.25% c.50% d.75% e.100% (c) 43.The Roberts’ hidden-line algorithm is an _____-space algorithm. a.image b.object (b) 44.The depth-buffer method typically uses additional storage which is _______ the storage required by the frame buffer. a.inconsequential relative to b.never greater than c.sometimes as large as (or larger than) (c) 45.What is/are characteristic of a “span” in the scan-line method? a.no polygon overlaps the span b.at most one polygon overlaps the span c.two or more polygons overlap the (entirety of the) span d.(all can be characteristic of a span) (d) 46.The depth-sorting method (as suggested by the name) sorts polygons in order by depth, and then writes them into the frame buffer, from farthest to nearest. a.true b.false (a)