egin{savequote}[75mm] parts of the skeletal model correspond

egin{savequote}75mm Try to be a filter, not a sponge.qauthor{Stephen Chbosky} end{savequote}chapter{Character Animation}section{Computer Animation}
ewthought{Computer animation}, or CGI animation, is the process used to generate animated images by using computer graphics. It is a subfield of computer graphics and animation. The more general term CGI (computer-generated imagery) refers to both static scenes and dynamic images while computer animation only refers to moving images.subsection{Methods for animation}Create a simplified representation of a character’s anatomy, which is analogous to a skeleton or stick figure. The position of each segment of the skeletal model is defined by animation variables, or Avars for short. In human and animal characters, many parts of the skeletal model correspond to the actual bones, but skeletal animation is also used to animate other things, such as facial features. The character “Woody” in Toy Story, for example, uses 700 Avars (100 in the face alone). The computer doesn’t usually render the skeletal model directly (it is invisible), but it does use the skeletal model to compute the exact position and orientation of that certain character, which is eventually rendered into an image. Thus by changing the values of Avars over time, the animator creates motion by making the character move from frame to frame.subsection{How to generate Avars?}egin{enumerate}    item extbf{Keyframing:} Manipulate the Avars directly. Set the Avars at strategic points (frames) and let the computer interpolate inbetween.    item extbf{Motion Capture:} Use a live action footage. Real performer acts the scene and the computer records his motion using video cameras and markers.end{enumerate}Starting from 2007, games and films are using either or both methods in production.subsection{Development Equipment}Computer animation can be created with a computer and an animation software. Some impressive animation can be achieved even with basic programs; however, the rendering can take a lot of time on an ordinary home computer.The first completely computer-animated television series was ReBoot in 1994, and the first completely computer-animated movie was Toy Story (1995).subsection{Detailed examples and pseudocode}In 2D computer animation, moving objects are often referred to as “sprites.” A sprite is an image that has a location associated with it. The location of the sprite is changed slightly, between each displayed frame, to make the sprite appear to move. The following pseudocode makes a sprite move from left to right:egin{lstlisting}var int x := 0, y := screenHeight / 2;while x < screenWidthdrawBackground()drawSpriteAtXY (x, y) // draw on top of the backgroundx := x + 5 // move to the rightend{lstlisting}section{Motion capture}Motion capture (Mo-cap for short) is the process of recording the movement of objects or people. It is used in military, entertainment, sports, medical applications, and for validation of computer vision and robotics. In filmmaking and video game development, it refers to recording actions of human actors, and using that information to animate digital character models in 2D or 3D computer animation. When it includes face and fingers or captures subtle expressions, it is often referred to as performance capture. In many fields, motion capture is sometimes called motion tracking, but in filmmaking and games, motion tracking usually refers more to match moving. extbf{Advantages:}egin{enumerate}    item More rapid.    item Complex movement and realistic physical interactions.    item Free software reduce cost.end{enumerate} extbf{Disadvantages}egin{enumerate}    item Specific hardware & software to obtain & process data.    item Capture system require specific space to operate.    item Easier to re-shoot the scene than to manipulate the data.    item Movement that doesn't follow physics laws can't be captured.    item Computer model must have same proportions of the capture subject or artefacts may occur.end{enumerate}section{Computer-assisted vs computer-generated animation}To animate means "to give life to" and there are two basic ways that animators commonly do this.Table ef{tab:ComputerAnimation}egin{table}!htcenteringcaption{label{tab:ComputerAnimation} Computer-assisted animation Vs Computer-generated animation}egin{tabular}{ |p{2cm}|p{5cm}|p{5cm}|  }hline& Computer-assisted animation & Computer-generated animation \hlineClass & two-dimensional (2D) animation & 3-dimensional (3D) animation \hlineDrawing method & either hand drawn (pencil to paper) or interactively drawn (drawn on the computer) using different assisting appliances & design an object or character with an X,Y and Z axis (no pencil to paper drawings) \hlineProcess & 1- creator will place drawings into different key frames which fundamentally create an outline of the most important movements & 1- object will be taken into a software. \& 2- the computer will interpolate the in-between frames (Tweening) & 2- Key-framing & tweening are carried by the computer. \& & 3- Animators can break physical laws by using mathematical algorithms to cheat mass, force and gravity rules. \hlineAdvantages & 1- cut down the time scale that traditional animation could take & 1- enhanced time scale and quality \& 2- still having the elements of traditional drawings of characters & 2- you can create a flock of creatures to act independently when created as a group.example: An animal's fur can be programmed to wave in the wind and lie flat when it rains instead of programming each strand of hair separately. \hlineExamples & Beauty and the Beast and Antz & Toy Story, The Incredibles and Shrek \hlineend{tabular}end{table}section{What Is CGI Animation}What Ever Happened to Plain Old Cartoons? cite{CGIAnimation}egin{enumerate}    item extbf{Traditional animation:} consisted of a whole team of animators who would draw and color images on "cels" – transparent sheets that were placed on top of a background image to create a multi-layered frame.    item extbf{2D CGI animation:} This simply involved computers doing what animators had been doing for decades – creating multiple frames of images each second in order to generate the visual effect of animation. Computers can modify large parts of a 2 dimensional image as "layers".example: GIF files (1990's)    item extbf{3D CGI animation:} With today's amazing CPU processing capabilities, computer animators are now able to create a 3 dimensional "model" to start with.Computers can calculate and modify very small sections of an object within a 3D worldend{enumerate}subsection{3D Modeling and Animation}Blender is an alternativeto 3Ds Max and LightWave. When it comes to 3D modeling and animation, there aren't very many open source free alternatives that are as powerful as their commercial counterparts. That's where Blender is the exception. See Figure ef{fig:Fig28}.egin{figure}centering  includegraphicswidth=0.7 extwidth{figures/Figure28.jpg}  caption{Editing 3D model in Blender}  label{fig:Fig28}end{figure}Blender is a very feature-full 3D animation program that can be used for a variety of uses, such as modeling, simulation, animation, and pretty much anything else that can be done on commercial software. What's also great about this software is its small installation size and ability to run on Windows, Linux, and OS X.However, the user interface needs a bit of work, as it does seem a bit un-intuitive and cluttered at the moment. You really need to sit down with this program for a while and learn how to use the application before you can harness its robust power.subsection{Keyframing in Blender} extbf{Keyframing:} Manipulate the Avars directly.Set the Avars at strategic points (frames) and let the computer interpolate between.For example, a key frame might indicate that the horizontal position of a cube is at 3m on frame 1.The user could then add another key on frame 10, specifying the cube's horizontal position at 20mBlender will automatically determine the correct position of the cube for all the frames between frame 1 and 10 depending on the chosen interpolation method (e.g. linear, bezier, quadratic, etc...). extbf{Adding Key Frames:} In the 3D View, pressing I will bring up a menu to choose what to add a key frame to.Hovering over a property and pressing I.RMB a value and choose Insert Keyframe from the menu. extbf{Removing Key Frames:} In the 3D View press Alt-I to remove keys on the current frame for selected objects.When the mouse is over a value press Alt-I.RMB a value and choose Delete Keyframe from the menu. extbf{Editing Key Frames:} For editing key frames go to the Graph Editor or to the Dopesheetsection{Pixar's animation process}Figure ef{fig:Fig29} shows the process for producing a Pixar's animation movie. egin{figure}centering  includegraphicswidth=.7 extwidth{figures/Figure29.jpg}  caption{Pixar's animation process}  label{fig:Fig29}end{figure}section{Computer Animation in Matlab}Creating an animation in MATLAB is done by creating a plot and periodically updating it. The simplest way to do this is by using while loops.Steps:egin{enumerate}    item Initialize all variables before the loop starts.    item Inside the loop:    egin{itemize}        item Update variables        item Use "Pause" command to refresh plot        item Configure the axis to keep them constant    end{itemize}end{enumerate}Example: extbf{Drawing Sin Wave}egin{lstlisting}%--------------------------------------------------------------------------%Script01a - Dancing Sinus%Creating Simple Animation in MATLAB%MATLAB script m-file creates an endless animation of sinusoidal wave whose%amplitude keeps on changing between -1 and 1.%--------------------------------------------------------------------------%CodeStart-----------------------------------------------------------------%Resetting MATLAB environment    close all;    clear all;    clc;%Creating base plot (sinusoidal plot)    x=0:10:360;    y=sind(x);%Declaring variable as a scale factor (amplitude) for base plot    theta=0;%Executing infinite loop to animate base plot    while 1        %Scaling base plot        theta=theta+1;        y_plot=y*sind(theta);        plot(x,y_plot);        %Preserving axis configuration        axis(0,360,-1.2,1.2);        %Delaying animation        pause(0.001);    end%CodeEnd-------------------------------------------------------------------end{lstlisting}When animation first started, each and every frame had to be drawn by hand.  Lead artists would drawn in key frames and other would fill in the frames in between. This process was extremely tedious, time consuming, and labor intensive.  However this was the only option for animators until technology began to improve.Computer animation is broken down into two categories, Computer generated animation this is when the animation is designed mainly on the computer system using animation and 3D graphics software, and computer assisted animation where older animations are computerised.

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