bouncing ball simulation

hello i have a working bouncing ball simulation but i would like to make it appear as though it is being squished when it hits the ground using a scale factor i tried using this if statement to squish the image when its hits the ground but it doesn't seem to work can someone help me fix it

if yc_o==.7
radius =.1;
end

%ee150_bball.m function ee150_bball %---------------------------------- % Constants %---------------------------------- radius = 0.7; % radius of the ball x0 = 0; % position of the center of the ball y0 = 10 + radius; w = 3*pi; % angular velocity (radians/sec.) g = 9.81; % gravitational acceleration constant in m/s

%---------------------------------- % Duration of the movie, frames per second, and other values %---------------------------------- duration = 15; framerate = 30; maxframes = duration * framerate + 1; dt = 1/framerate; % delta time between each frame

%---------------------------------- % Draw the initial ball, ground, and target %---------------------------------- % to draw the ball we'll have 512 points around the circumference n = 512;

% Creates a vector of 512 angles from [0 2*PI] radians to be used % to calculate the points on the circumference of the ball % rotate/spin the ball arg = [0 : 2*pi/n : 2*pi];

% Initial ball circumference X,Y coordinates matrix % We will never change this representation of the ball and just % rotate it for each frame % 8 Rows (1 for each sector) x 512/8 + 1 cols % Extra col => starting point of each sector is 0,0 xi = zeros(8,1+n/8); yi = zeros(8,1+n/8);

%=== For LAB completion==== % We'll cut the ball into 8 sectors filling each sector w/ a unique color % To do this, modify the xi, yi matrices such that the 1st point of each % row vector is 0,0 and the rest of the points are the circumference % points of the circle (i.e. use the 'arg' vector when calculating your % circumference points along with the 'radius' value). for i=1:8 j=(i-1)*n/8; k=(i*n/8) - 1; xi(i,:)=[0 radius*cos(arg(j+1:k+1))]; yi(i,:)=[0 radius*sin(arg(j+1:k+1))]; end

% Draw the 8 sectors filling them with color draw_ball(xi,yi); hold on; line([-1 20],[0 0], 'Color', 'b' ); % Draw the ground axis([-1 20 -1 20]); hold off;

% Now let the user pick the initial velocity and angle of the ball initV = input('Enter the initial velocity in m/s: '); angle = input('Enter the angle in degrees of the ball: '); rad = pi*angle/180; %=== For PRELAB completion==== vy = initV*sin(rad); % change these assignments appropriately for the ball's velocity vx = initV*cos(rad);

%---------------------------------- % Ball Path/Trajectory Calculation %---------------------------------- % xc and yc are coordinates of the center of the ball at each time xc = zeros(1,maxframes); yc = zeros(1,maxframes);

% theta = angle of rotation of the ball at each time frame theta = zeros(1,maxframes);

% sx, sy are the scaling factors of the ball in the x and y direction % at each time frame sx = ones(1,maxframes); sy = ones(1,maxframes);

% set the time = 0 t = 0;

%set initial position of the ball and its angle yc(1) = y0; xc(1) = x0; sx(1) = 1; sy(1) = 1; theta(1) = 0; % Calculate the velocity of the ball and change in angle at each timestep i % You will need to calculate theta, sx, sy, vx, vy, xc, yc, w, & status % You will also need to update i and t in each iteration % Continue calculation until the LAST position of the ball is past the edge % of the screen (i.e. 20 meters) or the current time has reached the % end of the movie (i.e. time less than (duration - dt) ) % Change the while loop below to perform these operations i=2; %=== For PRELAB completion==== while xc(i-1)<20+radius && t<=duration - dt [vx, vy, w, xc(i), yc(i), theta(i)] = physics_update(vx, vy, w, xc(i-1), yc(i-1), theta(i-1), dt, radius); i = i+1; t = t+dt; end % set the number of frames based on how many times the loop iterated numframes = i-1;

%plot the path of the center of the ball figure; plot(xc(1:numframes),yc(1:numframes)); hold on; line([-1 20], [0 0], 'Color', 'b'); % Draw the ground axis([-1 20 -1 20]);

%open a new figure; figure;

%---------------------------------- % Animation (Ball Rotation/Translation along trajectory path) %----------------------------------

% Rotated, translated ball circumference X,Y coordinates matrix at each % frame (we will rotate and traslate xi and yi at each frame to produce % these matrices) % 8 Rows (1 for each sector) x 512/8 + 1 cols x = zeros(8,1+n/8); y = zeros(8,1+n/8);

% Create the movie object mymovie = moviein(numframes);

% Draw the ball for EACH frame using trajectory/physics calculations % performed above % T = Translation matrix - move the ball to the (xc,yc) position % S = Scaling matrix - Scaling values for this frame % R = Rotation matrix - Rotation values for this frame for h = 1:numframes %=== For LAB completion==== % Calculate the geometric modification matrices T, S, R

% For each sector perform the affine transformation and place the
% result in the x,y vectors

T=[1 0 xc(h); 0 1 yc(h); 0 0 1];
R=[cos(theta(h)) -sin(theta(h)) 0; sin(theta(h)) cos(theta(h)) 0;  0 0 1;  ];
S=[sx(h),0,0;0,sy(h),0;0,0,1 ];
M=T*S*R;

for i=1:8
    for j=1:1+n/8
    p=[xi(i,j); yi(i,j); 1 ];
    p=M*p;
    x(i,j)=p(1);
    y(i,j)=p(2);
    end
end 
% Draw the 8 sectors filling them with color
draw_ball(x,y);
hold on;
line([-1 20], [0 0], 'Color', 'b');  % Draw the ground
axis([-1 20 -1 20]);
hold off;
a=[19.5 19.5]
b=[15 20]
line(a,b)

a=[19.5 19.5] b=[0 10] line(a,b)

% write the frame to the movie
mymovie(:,h)=getframe;

end

% Playback the movie movie(mymovie,1,framerate*2);

end

function [vx, vy, w, xc_o, yc_o, theta_o] = physics_update(vx, vy, w, xc_i, yc_i, theta_i, dt, radius) g = 9.81; %=== For PRELAB completion==== % Remember to check if the ball is hitting the ground and update your % velocities appropriately sx_o=1; sy_o=1; yc_o =yc_i+vy*dt; xc_o = xc_i+vx*dt; vy = vy-g*dt;

      if yc_o> 10 && yc_o<15
  a=[19.5 19.5]
  b=[0 10]
  line(a,b,'Color','g')

a=[19.5 19.5] b=[15 20] line(a,b,'Color','g')

else a=[19.5 19.5] b=[0 10] line(a,b,'Color','r')

a=[19.5 19.5] b=[15 20] line(a,b,'Color','r') end

%  vx = 0;
  theta_o = theta_i-w*dt;

      if yc_o <= radius 
          vy=-.85*vy
          yc_o=radius
          vx=.9*vx
          w=.8*w
      end
      % w=o;

end

% Expects 8xN x and y point matrices function draw_ball(x,y)

fill(x(1,:),y(1,:),'r'); hold on fill(x(2,:),y(2,:),'b'); hold on fill(x(3,:),y(3,:),'y'); hold on fill(x(4,:),y(4,:),'c'); hold on fill(x(5,:),y(5,:),'g') ; hold on fill(x(6,:),y(6,:),'w') ; hold on fill(x(7,:),y(7,:),'k') ; hold on fill(x(8,:),y(8,:),'m') ; hold off

%=== For LAB completion==== % Draw the 8 sectors filling them with color (turn hold on after the % first sector and turn hold off after the last sector

end

[Walter Roberson]

You posted what _looks_ like the same question, about an hour earlier. Perhaps you have updated the code between the two postings. One of the two questions would seem to be unneeded. Please delete one of the two.

The other copy of the question is at http://www.mathworks.com/matlabcentral/answers/22269-bouncing-ball-simulation

[Walter Roberson]

Note: messy code is as posted by original poster. The code in the other copy of the question was in better shape.