Computer Graphics
Unit - 5Curves, fractals and Animation
Q1) Explain Shading algorithms.A1) It is an implementation of the illumination model at the pixel points or polygon surfaces.It is used to display colors in graphics and also used to compute the intensities.It has two important ingredients as properties of the surface and properties of the illumination falling on it. In intensity computation the object illumination is the most significant thing.The diffuse illumination is the illumination which has the uniformly reflection from all the direction.The shading models are used to determine the shade of a point on the surface of an object in terms of number of attributes.Following figure 5.1 shows the energy comes out from the point on a surface.
Fig. no. 5.1 Q2) Explain Constant Intensity Shading and halftone shading algorithm in short.A2) It is a fast and simple method to render any object with polygon surfaces.It is also refereed as flat shading.For each polygon the single intensity is calculated.All points over the surfaces of the polygon are displayed with the same intensity value.It is generally used for the quick displaying of curved surfaces.It consists of illumination model to determine the shade entire polygon according to intensity value.It is easy to implement.
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Halftone AlgorithmIt is reprographic shading technique.It is used to simulate continues tone imagery through dots.The dots vary in the size or in spacing.Hence the dots represent the gradient like effect.Halftone is used to refer the image that is produced by this process.The range of color in continuous tone goes to infinite or in the range of gray.It reduces the visual reproduction of the image.The image that is reducing can be printed with only one color of ink or dot can be differs in size or spacing.The reproduction relies on the optical illusion.The halftone dots are so small that human eyes interprets it the patterned areas if they were smooth tones.Following figure 5.1.1 shows the halftone dots and human eye interpretation.
Fig. no. 5.1.1
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Q3) Explain Gouraud Algorithm.A3) It is also known as Gouraud shading when it renders a polygon surface by linear interpolating intensity value across the surface.It is an intensity interpolation scheme.The intensity values for each polygon are coordinates with the value of adjacent polygon along the common edges.Hence eliminating the intensities discontinuities happens like flat shading.Following are some calculations that are occurred in Gouraud shading.Determining average unit normal vector at each polygon vertexApply an illumination model to each vertex to determine the vertex intensityLinear interpolate the vertex intensities over the surface of the polygon.The normal vector obtains by averaging the surface normal of all polygons staring that vertex from each polygon vertex.Following figure 5.1.2 shows the Gouraud shading.
Fig. no. 5.1.2 Q4) Explain Phong Shading.A4) It is a more accurate method to render a polygon surface.The polygon surface that interpolates the normal vertex and then apply the illumination model to each surface point.This method is also known as the normal vector interpolation shading.It is used to display more realistic highlights on the surface.It is also use to reduce the match band effect.Following are the steps to render a polygon surface using phong shading:Determining average unit normal vector at each polygon vertex Linear and interpolate the vertex normal over the surface of the polygon. Apply an illumination model to each scan line to determine the projected intensities for surface points. Following figure 5.1.3 shows the phone shading between two vertices.
Fig. no. 5.1.3The evaluation of normal between the scam lines are determined by the incremental method along with each scan line.The illumination model is applied on each of the scan line to determine the surface intensity at that point.The accurate result is produced by the intensity calculation using approximated normal vector at each point along the scan line instead of using the direct interpolation of intensities.The phone shading requires more calculations than other shading algorithms.
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Fig. no. 5.1.3The evaluation of normal between the scam lines are determined by the incremental method along with each scan line.The illumination model is applied on each of the scan line to determine the surface intensity at that point.The accurate result is produced by the intensity calculation using approximated normal vector at each point along the scan line instead of using the direct interpolation of intensities.The phone shading requires more calculations than other shading algorithms. Q5) Explain Animation concept in short.A5) Animation is the movement on the screen of the display device.Animation means giving life to any object in graphics.It is created by displaying a sequence of still images.Animation is the technique of designing, drawing, making layout and preparation of photographic series that are integrated to create a multimedia and games.It connects the exploitation and the management of still images to generate the illusion of movement.A person who creates the animation is called animator.Conventional and Computer Based AnimationConventional Animation:The conventional model has unlimited technology and computing techniques.It is faster than computer animation for high quality.The complete control of drawing and motion in conventional animation.The conventional animation is limited by artistic ability.Computer Animation:In computer animation many frames can be calculated instead of drawing.Many variations can be tried quickly in computer.The complex 3D models are easy to draw in computer animation as in this don’t have to draw different views.In computer animation there are fewer tedious steps. Q6) Write short note on Animation Sequences.A6) Following are some steps of designing the animation sequences.1. Layout of StoryboardIt is an action layout that is used to illustrate the motion sequence as a set of basic events which are to acquire place.It is an animation that selects the storyboard layout.Hence the storyboard layout comprises the set of rough sketches.2. Definition of ObjectThe definition of object is applied on all the participant objects in action.The objects can be treated as fundamental shapes or related to movement with shapes.3. Specification of Key FrameIt is detailed drawing of the scene at an exact time in the animation sequence.In each key frame all objects are positioned according to time for that frame.In the action several key frames are used at the extreme positions and other keys are spaced.Hence the time interval of key frame is not great.More key frame is given for intricate motion than for easy and slowly varying motions.4. In Between Frames GenerationThe in-among frames are the frames are the middle frame in key frames.Most of the among frames are based on the media that are utilized to display animation.Commonly the 24 frames are needed per second and graphic terminal are refreshed on the rate of 30 to 60 frames per second.The time interval for the motion is set up and therefore 3 to 5 among for each pair of key frames.Several key frames can be duplicated by identified the speed for motion. Q7) Write short note on Functions and Animation Languages.A7) The animation sequences are handled with the set of animation routines.Following are some languages that are used as animation languages.C Lisp Pascal FORTRAN Several animation languages have been developed.The animation functions are used as graphics editor, key frame generator, in-between generator and standard graphic routines.The graphic editor is used to design and modify object shapes using spline surfaces, constructive solid geometry methods or other representation. Q8) Write short note on Key Frame Systems.A8) The changes in animation will be defined by key framing.In animation every frame is the key frame which is created frame by frame.In 3D animation the exact position of the given object is not specify on every single frame.For specifying this position, they create key frames.Key frame is important for changing size, shape or the other properties of the object in animation.The computer then search out all the in-between frames and saves an extreme amount of time for animator.
Q9) Explain Morphing.A9) The transformation of the object from one form to another form is called as morphing.It most complicated transformation.It is shortened from the metamorphosis.It looks like the two images are mixed into each other as fluid mixes.In technical terms the images are distorted and fade occurs between them.The morphing can be applied on any of the motion that changes the shape. Q10) Write short note on Motion Specification.A10) In animation the motion can be expressed in various terms.Direct Motion Specification:It is a straight forward method to define a motion.In this rotation angles and translation vectors are given explicitly.The matrices are used to translate the position of coordinates.It is a simple method used by simple user programmed animation sequences.Goal Directed System:The motion which describes the action in animation is defined by the goal directed system.It specifies the motion parameters which have given the goal of the animation.For example, if we want to move an object from one position to destination, we use goal directed system.The components motion will be interpreted as a accomplished selected task in goal directed system. Kinematics and Dynamics:Kinematics and the dynamics are also used to construct animation sequences.In kinematics the motion parameters positions, velocity and without references force which causes the motion are specified.For constant velocity the motion of rigid bodies is designated by giving initial position and velocity vector for each object.In dynamics the specification of forces is required which produces the velocities and acceleration. Q11) Explain Methods of Controlling Animation.A11) Following are methods of controlling animation.Explicitly declared controlThe transformation that specified by object to object.The frame level by specifying key frames and methods for interpolating between them.Procedural controlIt is based on communication among different objects.Each object having knowledge about static or dynamic properties of other objects.It can be used to ensure consistency. Constraint based controlIn constraint-based control, many objects movement in the real world are determined by other objects which they come in contact.The object motion can be control by environment-based constraint.Analyzing live action-based controlThe examining the motion of object in the real world is achieved by the control.The animated movies use the frame-by-frame method to trace the live action movement.Kinematics and dynamic controlIt refers to the velocity and position of points.Dynamics takes into account the physical laws that governs kinematics.Frame-By-Frame Animation TechniqueThe changes are made in every key frame to create the illusion of movement.It increases the file size rapidly because it has to store each key frame.It is tedious to do on hand drawn cel animation where each drawing should present on each sheet paper.Real-Time Animation TechniquesIt is also known as real time capture or lice animation.It is a process of using motion capture system to puppet a 3D character lives in real time.Previsualization uses the real time animation technique so the director can see the actor is performing mocap actor’s animation.It allows to present at game cons, appear on talk shows, and speak at keynotes.It has ability to bring 3D characters to life.
Following figure 5.2.3 shows the key frames that are created by computer and user.
Fig. no. 5.2.3 |
Q12) Which are the Gaming Platforms?A12) The platform where users can play game is known as gaming platform.There are some gamming platform as follows.Playstation Xbox PC
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