Animation_of_an_Engine.m

%% Math 111: MATLAB (Summer 2019)
% TW Judge (twjudge@comcast.net)
%
%
% Lecture: Chapter 6 Supplemental: Animation Using movie Function
%          Example #1: Animation of an Engine
%
%
% This program presents a method for animating the motion of an engine
% cylinder and saves the movie as a video file.
%
%
% ----- START OF PROGRAM -----
%
% Initiate Workspace
clear, clc
%
% We Opt to Divide the Engine Cycle Into 50 Frames...
n = 50;
theta = linspace(0, 2*pi, n);
a = 1.1;              % Crank of engine/piston  
b = 2.7;              % Link of engine/piston  
c = 0.6;              % Radius of cylinder  
d = 0.4;              % Half height of piston length  
aX = a*cos(theta);    % Both aX and aY are the coordinates of a point on  
aY = a*sin(theta);    %  circle where the crank attaches to the link  
p = aX + sqrt(b^2 - aY.^2);     % Calculates Distance traveled by piston
limits = [-a, a+b+d, -a, a];    % Determines limits for axes...
%                                   - horizontal goes from -a to a+b+d;
%                                   - vertical goes from -a to a/  
cmap = colormap;                % Retrieve current colormap parula  
nc = length(colormap) - 1;
%
% Generate the Successive Images Required for the Animation 
for k = 1:n      
    plot(aX, aY, 'k:')              % Draw plot of Point A 
    hold on        
    cylinderX = [a, a+b+d, a+b+d, a];  % Current axis held so not erased 
    cylinderY = [-c, -c, c, c];        % Current axis held so not erased     
    plot(cylinderX, cylinderY, 'k')      % Draw cylinder    
    pistonX = [p(k)-d, p(k)+d, p(k)+d, p(k)-d, p(k)-d];     
    pistonY = [-c, -c, c, c, -c];     
    fill(pistonX, pistonY, 'c');         % Draw cylinder space    
    fuelX = [p(k)+d, a+b+d, a+b+d, p(k)+d, p(k)+d];       
    fuelY = [-c, -c, c, c, -c];     
    color = cmap(ceil((p(k)-b+a) / (2*a)*(nc - 1)),:);    
    fill(fuelX, fuelY, color)            % Draw fuel      
    crankX = [0, aX(k)];               % Draw crank     
    crankY = [0, aY(k)];    
    plot(crankX, crankY, 'ko', 'LineWidth', 4)     
    linkX = [aX(k), p(k)];             % Draw link       
    linkY = [aY(k), 0];     
    plot(linkX, linkY, 'ko', 'Linewidth', 4)   
    axis(limits)    
    axis off equal                       % Removes Axes and sets lengths
%                                           of units equal in both the x-
%                                           and y-axis
% ...And Capture Each Image Generated by Each Loop Iteration...    
    Frames(k) = getframe;
    hold off  
end
movie(Frames, 5, 30)
%
% Create the Video Object (so we can save frames as a video file)  
videoObj = VideoWriter('Engine');
% ...Open a Video File...     
     open(videoObj);
% ...And Write the Frames to the File...    
     writeVideo(videoObj, Frames);
% ...And Then Close the File...    
     close(videoObj);
%
% ----- END OF PROGRAM -----