DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI

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1 DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI Department of Computer Science and Engineering CS6504-COMPUTER GRAPHICS Anna University 2 & 16 Mark Questions & Answers Year / Semester: III / V Regulation: 2013 Academic year:

2 UNIT V ANIMATION AND REALISM PART - A 1. Define computer graphics animation. Computer graphics animation is the use of computer graphics equipment where the graphics output presentation dynamically changes in real time. This is often also called real time animation. 2. What is tweening? It is the process, which is applicable to animation objects defined by a sequence of points, and that change shape from frame to frame. 3. Define -Frame. One of the shape photographs that a film or video is made of is known as frame. 4. What is the normal speed of a visual animation? Visual animation requires a playback of at least 25 frames per second. 5. What are the different tricks used in computer graphics animation? a. Color look Up Table manipulation b. Bit plane manipulation c. Use of UDCS d. Special drawing modes e. Sprites f. Bit blitting 6. What is solid modeling? The construction of 3 dimensional objects for graphics display is often referred to as solid modeling. 7. What is an intuitive interface? The intuitive interface is one, which simulates the way a person would perform a corresponding operation on real object rather than have menu command. 8. What is Sprite? A Sprite is graphics shape in animation and games programs. Each sprite provided in the system has its own memory area similar to but smaller than pixel 9. What is the UDC technique? UDC stands for User Defined Character set. It is graphics animation trick, which is used in early microcomputer system. 10. What is computer graphics realism? The creation of realistic picture in computer graphics is known as realism.it is important in fields such as simulation, design, entertainments, advertising, research, education, command, and control. 11. How realistic pictures are created in computer graphics? To create a realistic picture, it must be process the scene or picture through viewing-coordinate transformations and projection that transform three-dimensional viewing coordinates onto two-dimensional device coordinates. 12. What is Fractals? A Fractal is an object whose shape is irregular at all scales.

3 13. What is a Fractal Dimension? Fractal has infinite detail and fractal dimension. A fractal imbedded in n-dimensional space could have any fractional dimension between 0 and n. The Fractal Dimension D= LogN / Log S Where N is the No of Pieces and S is the Scaling Factor. 14. What is random fractal? The patterns in the random fractals are no longer perfect and the random defects at all scale. 15. What is geometric fractal? A geometric fractal is a fractal that repeats self-similar patterns over all scales. 16. What is Koch curve? The Koch curve can be drawn by dividing line into 4 equal segments with scaling factor 1/3. and middle 2 segments are so adjusted that they form adjustment sides of an equilateral triangle. 17. What is turtle graphics program? The turtle program is a Robert that can move in 2 dimensions and it has a pencil for drawing. The turtle is defined by the following parameters. Position of the turtle (x, y) Heading of the turtle 0 the angle from the x axis. 18. What is graftals? Graftals are applicable to represent realistic rendering plants and trees. A tree is represented by a String of symbols 0, What is a Particle system? A particle system is a method for modeling natural objects, or other irregularly shaped objects, that exhibit fluidlike properties. Particle systems are suitable for realistic rendering of fuzzy objects, smoke, sea and grass. 20. Give some examples for computer graphics standards. CORE The Core graphics standard GKS -- The Graphics Kernel system PHIGS The Programmers Hierarchical Interactive Graphics System. GSX The Graphics system extension NAPLPS The North American presentation level protocol syntax. PART-B 1. Explain in detail the design of animation sequences with various animation functions. Animation means giving life to any object in computer graphics. It has the power of injecting energy and emotions into the most seemingly inanimate objects. Computer-assisted animation and computergenerated animation are two categories of computer animation. It can be presented via film or video. The basic idea behind animation is to play back the recorded images at the rates fast enough to fool the human eye into interpreting them as continuous motion. Animation can make a series of dead images come alive. Animation can be used in many areas like entertainment, computer aided-design, scientific visualization, training, education, e-commerce, and computer art. Animation Techniques Animators have invented and used a variety of different animation techniques. Basically there are six animation technique which we would discuss one by one in this section.

4 Traditional Animation (frame by frame) Traditionally most of the animation was done by hand. All the frames in an animation had to be drawn by hand. Since each second of animation requires 24 frames (film), the amount of efforts required to create even the shortest of movies can be tremendous. Keyframing In this technique, a storyboard is laid out and then the artists draw the major frames of the animation. Major frames are the ones in which prominent changes take place. They are the key points of animation. Keyframing requires that the animator specifies critical or key positions for the objects. The computer then automatically fills in the missing frames by smoothly interpolating between those positions. Procedural In a procedural animation, the objects are animated by a procedure a set of rules not by keyframing. The animator specifies rules and initial conditions and runs simulation. Rules are often based on physical rules of the real world expressed by mathematical equations. Behavioral In behavioral animation, an autonomous character determines its own actions, at least to a certain extent. This gives the character some ability to improvise, and frees the animator from the need to specify each detail of every character's motion. Performance Based (Motion Capture) Another technique is Motion Capture, in which magnetic or vision-based sensors record the actions of a human or animal object in three dimensions. A computer then uses these data to animate the object. This technology has enabled a number of famous athletes to supply the actions for characters in sports video games. Motion capture is pretty popular with the animators mainly because some of the commonplace human actions can be captured with relative ease. However, there can be serious discrepancies between the shapes or dimensions of the subject and the graphical character and this may lead to problems of exact execution. Physically Based (Dynamics) Unlike key framing and motion picture, simulation uses the laws of physics to generate motion of pictures and other objects. Simulations can be easily used to produce slightly different sequences while maintaining physical realism. Secondly, real-time simulations allow a higher degree of interactivity where the real person can maneuver the actions of the simulated character. In contrast the applications based on key-framing and motion select and modify motions form a precomputed library of motions. One drawback that simulation suffers from is the expertise and time required to handcraft the appropriate controls systems.

5 Key Framing A keyframe is a frame where we define changes in animation. Every frame is a keyframe when we create frame by frame animation. When someone creates a 3D animation on a computer, they usually don t specify the exact position of any given object on every single frame. They create keyframes. Keyframes are important frames during which an object changes its size, direction, shape or other properties. The computer then figures out all the in-between frames and saves an extreme amount of time for the animator. The following illustrations depict the frames drawn by user and the frames generated by computer. Morphing The transformation of object shapes from one form to another form is called morphing. It is one of the most complicated transformations. 2. Write short notes on raster animation. In computer animation, the term "raster graphics" refers to animation frames made of pixels rather than scalable components, such as vertices, edges, nodes, paths or vectors. Storing images as pixels rather than vectors or vertices enables much deeper and more realistic lighting and color because the computer doesn't have to render each frame in real time as it does in a 3-D video game. However, because a fast PC can take 10 to 20 minutes to render one frame, rendering an entire animation usually requires a network of render nodes. Bitmaps and Scalable Vector Graphics Raster animation doesn't only refer to 3-D graphics, although demand for 2-D animation in movies, TV, video games and commercials has decreased since processing power has become affordable enough to render 3-D animations on a small budget. A raster image is simply another word for a bitmap, or pixelbased image. In comparison, a vector image is a 2-D picture created in a scalable vector graphics editor such as Adobe Illustrator or open source Inkscape. SVG files take up less disk space than bitmaps because they only store the paths that delineate the shapes in a picture, whereas bitmaps store data for every pixel. Bitmaps store all the depth and subtlety of light that the image resolution allows, while SVGs have simple, cartoonlike colors. File Storage The term "raster image" refers to the way the image is stored rather than how it's displayed. When your video card renders a frame of a video game, you see the same pixels you'd see if you pre-rendered the frame using the same settings. The file read by the game stores the image as an enormous array of vertices, and the video game contains software routines that move the vertices based on events in the game. Video games sacrifice realism for smoothness during game play, but they often contain prerendered movies with fully realized graphics. These scenes, stored as MPEG or a similar format, usually cause modern game sizes to exceed 1GB.

6 Traditional Raster Animation Before 3-D animation became affordable, animated films and TV shows were mostly hand-painted, but video games used low-detail raster animation to store graphics on a cartridge or disc. Video game artists in the 1980s and 1990s animated these character bitmaps using sprite sheets, which enabled them to separate all the moving objects in the game. The game's software routines played the frames in each object's sprite sheet independently of one another so that the game could react to the player's actions. Modern Raster Animation Many modern cartoons use raster animation to add color to hand-drawn animation cels. Each animation frame is either scanned into a computer or sketched on a graphics tablet, and the entire animation is stored as a digital movie. Programming languages such as Flash, HTML and Java include animation libraries that generate 2-D animations based on user input events, such as mouse clicks or keystrokes. Like vector graphics, these generated animations can be scaled to fit any window, whereas pre-rendered raster graphics have a predetermined resolution and become pixelated when scaled up. 3. Write short notes on key frame systems. A key frame in animation and filmmaking is a drawing that defines the starting and ending points of any smooth transition. The drawings are called "frames" because their position in time is measured in frames on a strip of film. A sequence of key frames defines which movement the viewer will see, whereas the position of the key frames on the film, video, or animation defines the timing of the movement. Because only two or three key frames over the span of a second do not create the illusion of movement, the remaining frames are filled with in be tweens. Use of key frames as a means to change parameters In software packages that support animation, especially 3D graphics, there are many parameters that can be changed for any one object. One example of such an object is a light (In 3D graphics, lights function similarly to real-world lights. They cause illumination, cast shadows, and create specular highlights). Lights have many parameters including light intensity, beam size, light color, and the texture cast by the light. Supposing that an animator wants the beam size of the light to change smoothly from one value to another within a predefined period of time, that could be achieved by using key frames. At the start of the animation, a beam size value is set. Another value is set for the end of the animation. Thus, the software program automatically interpolates the two values, creating a smooth transition. Video editing In non-linear digital video editing, as well as in video compositing software, a key frame is a frame used to indicate the beginning or end of a change made to the gsignal. For example, a key frame could be set to indicate the point at which audio will have faded up or down to a certain level. Video compression

7 In video compression, a key frame, also known as an "intra-frame", is a frame in which a complete image is stored in the data stream. In video compression, only changes that occur from one frame to the next are stored in the data stream, in order to greatly reduce the amount of information that must be stored. This technique capitalizes on the fact that most video sources (such as a typical movie) have only small changes in the image from one frame to the next. 4. Write short notes on Koch curves. The Koch snowflake (also known as the Koch curve, Koch star, or Koch island) is a mathematical curve and one of the earliest fractal curves to have been described. It is based on the Koch curve, which appeared in a 1904 paper titled "On a continuous curve without tangents, constructible from elementary geometry" (original French title: Sur une courbe continue sans tangente, obtenue par une construction géométrique élémentaire) [citation needed] by the Swedish mathematician Helge von Koch. The progression for the area of the snowflake converges to 8/5 times the area of the original triangle, while the progression for the snowflake's perimeter diverges to infinity. Consequently, the snowflake has a finite area bounded by an infinitely long line. Construction The Koch snowflake can be constructed by starting with an equilateral triangle, then recursively altering each line segment as follows: 1. divide the line segment into three segments of equal length. 2. draw an equilateral triangle that has the middle segment from step 1 as its base and points outward. 3. remove the line segment that is the base of the triangle from step 2. After one iteration of this process, the resulting shape is the outline of a hexagram. The Koch snowflake is the limit approached as the above steps are followed over and over again. The Koch curve originally described by Helge von Koch is constructed with only one of the three sides of the original triangle. In other words, three Koch curves make a Koch snowflake. 5. Write short notes on types of curves. A curve is an infinitely large set of points. Each point has two neighbors except endpoints. Curves can be broadly classified into three categories explicit, implicit, and parametric curves. Implicit Curves Implicit curve representations define the set of points on a curve by employing a procedure that can test to see if a point in on the curve. Usually, an implicit curve is defined by an implicit function of the form f(x, y) = 0 It can represent multivalued curves (multiple y values for an x value). A common example is the circle, whose implicit representation is x 2 + y 2 - R 2 = 0

8 Explicit Curves A mathematical function y = f(x) can be plotted as a curve. Such a function is the explicit representation of the curve. The explicit representation is not general, since it cannot represent vertical lines and is also single-valued. For each value of x, only a single value of y is normally computed by the function. Parametric Curves Curves having parametric form are called parametric curves. The explicit and implicit curve representations can be used only when the function is known. In practice the parametric curves are used. A two-dimensional parametric curve has the following form P(t) = f(t), g(t) or P(t) = x(t), y(t) The functions f and g become the (x, y) coordinates of any point on the curve, and the points are obtained when the parameter t is varied over a certain interval [a, b], normally [0, 1]. 6. Write short notes on space filling curves. A Hilbert curve (also known as a Hilbert space-filling curve) is a continuous fractal space-filling curve first described by the German mathematician David Hilbert in 1891,as a variant of the space-filling Peano curves discovered by Giuseppe Peano in 1890.Because it is space-filling, its Hausdorff dimension is (precisely, its image is the unit square, whose dimension is 2 in any definition of dimension; its graph is a compact set homeomorphic to the closed unit interval, with Hausdorff dimension 2).It is the approximation to the limiting curve. The Hilbert curve is a space filling curve that visits every point in a square grid with a size of 2 2, 4 4, 8 8, 16 16, or any other power of 2. It was first described by David Hilbert in Applications of the Hilbert curve are in image processing: especially image compression and dithering. It has advantages in those operations where the coherence between neighbouring pixels is important (see Douglas Voorhies's contribution to the "Graphic Gems" series). The Hilbert curve is also a special version of a quadtree; any image processing function that benefits from the use of quadtrees may also use a Hilbert curve. Cups and joins The basic elements of the Hilbert curves are what I call "cups" (a square with one open side) and "joins" (a vector that joins two cups). The "open" side of a cup can be top, bottom, left or right. In addition, every cup has two end-points, and each of these can be the "entry" point or the "exit" point. So, there are eight possible varieties of cups. In practice, a Hilbert curve uses only four types of cups. In a similar vein, a join has a direction: up, down, left or right. A first order Hilbert curve is just a single cup (see the figure on the left). It fills a 2 2 space. The second order Hilbert curve replaces that cup by four (smaller) cups, which are linked together by three joins (see the figure on the right; the link between a cup and a join has been marked with a fat dot in the figure). Every next order repeats the process or replacing each cup by four smaller cups and three joins.

$It would therefore be sufficient to draw half of the Hilbert curve. 7. Write short notes on fractals. Fractals are very complex pictures generated by a computer from a single formula.$

9 The function presented below (in the "C" language) computes the Hilbert curve. Note that the curve is symmetrical around the vertical axis. It would therefore be sufficient to draw half of the Hilbert curve. 7. Write short notes on fractals. Fractals are very complex pictures generated by a computer from a single formula. They are created using iterations. This means one formula is repeated with slightly different values over and over again, taking into account the results from the previous iteration. Fractals are used in many areas such as Astronomy For analyzing galaxies, rings of Saturn, etc. Biology/Chemistry For depicting bacteria cultures, Chemical reactions, human anatomy, molecules, plants, Others For depicting clouds, coastline and borderlines, data compression, diffusion, economy, fractal art, fractal music, landscapes, special effect, etc. Generation of Fractals Fractals can be generated by repeating the same shape over and over again as shown in the following figure. In figure (a) shows an equilateral triangle. In figure (b), we can see that the triangle is repeated to create a star-like shape. In figure (c), we can see that the star shape in figure (b) is repeated again and again to create a new shape. We can do unlimited number of iteration to create a desired shape. In programming terms, recursion is used to create such shapes.

10 Geometric Fractals Geometric fractals deal with shapes found in nature that have non-integer or fractal dimensions. To geometrically construct a deterministic (nonrandom) self-similar fractal, we start with a given geometric shape, called the initiator. Subparts of the initiator are then replaced with a pattern, called the generator. As an example, if we use the initiator and generator shown in the above figure, we can construct good pattern by repeating it. Each straight-line segment in the initiator is replaced with four equal-length line segments at each step. The scaling factor is 1/3, so the fractal dimension is D = ln 4/ln Also, the length of each line segment in the initiator increases by a factor of 4/3 at each step, so that the length of the fractal curve tends to infinity as more detail is added to the curve as shown in the following figure

Animation. Representation of objects as they vary over time. Traditionally, based on individual drawing or photographing the frames in a sequence

Animation. Representation of objects as they vary over time. Traditionally, based on individual drawing or photographing the frames in a sequence 6 Animation Animation Representation of objects as they vary over time Traditionally, based on individual drawing or photographing the frames in a sequence Computer animation also results in a sequence