Animation Animation refers to the movement on the screen of the display device created by displaying a sequence of still images. Animation is the technique of designing, drawing, making layouts and preparation of photographic series which are integrated into the multimedia and gaming products. Animation connects the exploitation and management of still images to generate the illusion of movement. A person who creates animations is called animator. He/she use various computer technologies to capture the pictures and then to animate these in the desired sequence. Generating Animations Using Raster Operations ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ We can also generate real-time raster animations for limited applications using block transfers of a rectangular array of pixel values. A simple method for translating an object from one location to another in the xy plane is to transfer the group of pixel values that define the shape of the object to the new location Sequences of raster operations can be executed to produce realtime animation for either two-dimensional or three-dimensional objects, so long as we restrict the animation to motions in the projection plane. Then no viewing or visible-surface algorithms need be invoked. We can also animate objects along two-dimensional motion paths using color table transformations. Here we predefine the object at successive positions along the motion path and set the successive blocks of pixel values to color-table entries. The pixels at the first position of the object are set to a foreground color, and the pixels at the other object positions are set to the background color . Then the animation is then accomplished by changing the color-table values so that the object color at successive positions along the animation path becomes the foreground color as the preceding position is set to the background color Computer Animation Languages ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ Animation functions include a graphics editor, a key frame generator and standard graphics routines. The graphics editor allows designing and modifying object shapes , using spline surfaces, constructive solid geometry methods or other representation schemes. Scene description includes the positioning of objects and light sources defining the photometric parameters and setting the camera parameters. Action specificat ion involves the layout of motion paths for the objects and camera. Keyframe systems are specialized animation languages designed dimply to generate the in betweens from the user specified keyframes. Parameterized systems allow object motion characterist ics to be specified as part of the object definitions. The adjustable parameters control such object characteristics as degrees of freedom motion limitations and allowable shape changes. Scripting systems allow object specifications and animation sequence s to be defined with a user input script. From the script, a library of various objects and motions can be constructed. There is several animation languages already develop. All of them can be categories under three groups: 1. linear list notations language: It is the specially animation supporting language. Each event in the animation is described by start and ending frame number and an action that is to take place (event). The example of this type of languages is SCEFO (scene format). For example: 42, 53, B, rotate, “palm”, 1, 30 Here, 42 => start frame no. 53 => ending frame no. B => table. Rotate => action. Palm => object. 1 => start angle. 30 => end angle. 2. General purpose languages: The high level computer languages which are developed for the normal application software development also have the animation supporting features along with graphics drawing, For example QBASIC, C, C++, java etc. 3. Graphical language: it is also computer high level language and especially develop for graphics drawing and animation has been already develop for e.g. AutoCAD. 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 Morphing: Morphing is an animation function which is used to transform object shape from one form to another is called Morphing. It is one of the most complicated transformations. This function is commonly used in movies, cartoons, advertisement, and computer games. Example: face of young person is converted into aged person The process of Morphing involves three steps: 1. In the first step, one initial image and other final image are added to morphing application as shown in fig: Ist & 4th object consider as key frames. 2. The second step involves the selection of key points on both the images for a smooth transition between two images as shown in 2nd object. 3. In the third step, the key point of the first image transforms to a corresponding key point of the second image as shown in 3rd object of the figure. Motion Specification In Computer Animation There are several ways in which the motions of objects can be specified in an animation system. We can define motion in very explicit tems, or We can use more abstract or more general approaches. Direct motion specification : The most straightforward method for defining a motion sequence is direct specification of the motion paremeters. Here, We explicitly give the rotation angles and translation vectors. Then the geometric transformation matrices are applied to transform co-ordinate positions. Alternatively, We could use an approximating equation to specify certain kinds of motions. These methods can be used for simple user programmed animation sequencs. Goal-directed systems : At the opposite extreme, We can specify the motions that are to take place in general terms that abstractly describe the actions. these systems are referred to as goal directed because they determine specific motion parameters given the goals of the animation. For example, We could specify that we want an object to "walk " or to "run" to a particular destination. Or We could state that we want an object to "pick up " some other specified object. The inpute directive are then interpreted in term of component motions that will accomplish the selected task. Human motion, for instance, can be defined as a heirarchical structure of sub motion for the toros, limbs,and so forth. Kinematics and dynemics : We can also construct animation sequences using kinematic or dynemic descriptions. With a kinematic description, we specify the animation by giving motion parameters position, velocity, and acceleration) without reference to the forces that cause the motion. for constant velocity (zero acceleration), we designate the motions of rigid bodies in a scene by giving an initial position and velocity vector for each objects. An alternate apporach is to use inverse kinematics. Here, we specify the initial and final positions of objects at specified times and the motion parameters are computed by the system . For example, assuming zero acceleration , we can determine the constant velocity that will accomplish the movement of an object from the initial position to the final position. Dynamic descriptions on the other hand, require the specification of the forces that produce the velocities and acceleration. Descriptions of object behavior under the are generally referred to as a physically based modeling. Example of forces affecting object motion include electromagnetic, gravitational, friction, and other mechanical forces. Object motion are obtained from the forces equations describing physical laws, such as newton's law of motion for gravitational ang friction processes, euler or navier-stokes equations describing fluid flow, and maxwell 's equations for electromagnetic forces. For example, the general form os newton's second law for a particle of mass m is F = d(mv)/dt with F as the force vector, and v as the velocity vector. If mass is constant, we solve the equation F=ma, where a is the acceleration vector. otherwise, mass is a function of time, as in relativistic motions of space vehicles that consume measurable amounts of fuel per unit time. We can also use inverse dynemics to obtain the forces, given the initial and final positions of objects and the type of motion. Application of physically based modeling include complex rigid-body systems and such nonrigid systems as cloth and plastic materials. Typically, numerical methods are used to obtain the motion parameters incrementally from the dynemical equations using initial conditions or boundary values.
