using keyboard to control

figure;
bottom = [-2 2 2 -2 -2; 4 4 -4 -4 4];  
blade1 = [-0.5 0.5 0.5 -0.5 -0.5; 5.5 5.5 2.5 2.5 5.5];
drawshape(bottom, 'g')
hold on
drawshape(blade1, 'r')
hold on
stopRotation = false;
for i = 1:1000 
    if stopRotation == true
        break; % 如果 stopRotation 为 true，停止旋转
    end
    
    clf; % 清除当前图形窗口
    drawshape(bottom, 'g')
    fill(bottom(1, :), bottom(2, :), 'g');
    hold on
    
    % rotate and draw the blade
    for j = 1:4
        bladei = rotateabout(blade1, 0, 6, (j - 1) * pi/2 + i * pi/180);
        drawshape(bladei, 'r')
        fill(bladei(1, :), bladei(2, :), 'r');
        hold on
    end
    % set axis
    axis([-10 10 -10 10])
    axis square
    set(gca, 'Color', [0.7 0.85 1]);
    
    % 控制每一帧显示的时间
    pause(0.001) 
end
set(gcf, 'KeyPressFcn', @keyPressCallback); % 设置当前图形窗口的按键回调函数
% 按键回调函数
function keyPressCallback(~, event)
if strcmp(event.Key, 's') % 如果按下回车键
    stopRotation = true; % 设置 stopRotation 为 true
end
end
function drawshape(matrix, colour)
x = matrix(1,:);
y = matrix(2,:);
plot(x, y, colour)
end
function newShape = translateShape(shape, xShift, yShift)
x = shape(1,:) + xShift;
y = shape(2,:) + yShift;
newShape = [x; y];
end
function newShape = rotateShape(shape, a)
reflectMatrix = [cos(a) -sin(a); sin(a) cos(a)];
newShape = reflectMatrix * shape;
end
function newShape = rotateabout(shape, p, q, a)
shape1 = translateShape(shape, -p, -q);
shape2 = rotateShape(shape1, a);
newShape = translateShape(shape2, p, q);
end

Answer 1

[Hassaan]

% Execute the animation function
% fan_animation();

function fan_animation()

    global stopRotation;  % Declare as global variable
    stopRotation = false; % Initialize the variable

    % Initialize the figure
    figure;
    
    % Set up key press callback function for the current figure
    set(gcf, 'KeyPressFcn', @keyPressCallback);

    % Define the shapes using matrices
    bottom = [-2 2 2 -2 -2; 4 4 -4 -4 4];  
    blade1 = [-0.5 0.5 0.5 -0.5 -0.5; 5.5 5.5 2.5 2.5 5.5];
    
    % Draw the initial shapes
    drawshape(bottom, 'g');
    hold on;
    drawshape(blade1, 'r');
    hold on;
    
    % Initialize stopRotation variable
    stopRotation = false;
    
    % Main loop for animation
    for i = 1:1000 
        if stopRotation
            break; % If stopRotation is true, stop the rotation
        end

        clf; % Clear the current figure
        drawshape(bottom, 'g');
        fill(bottom(1, :), bottom(2, :), 'g');
        hold on;

        % Rotate and draw the blade
        for j = 1:4
            bladei = rotateabout(blade1, 0, 6, (j - 1) * pi/2 + i * pi/180);
            drawshape(bladei, 'r');
            fill(bladei(1, :), bladei(2, :), 'r');
            hold on;
        end
        
        % Set axis properties
        axis([-10 10 -10 10]);
        axis square;
        set(gca, 'Color', [0.7 0.85 1]);
        
        % Control the display time of each frame
        pause(0.001); 
    end
    

end

% Key press callback function
function keyPressCallback(~, event)
    global stopRotation;

    disp("keyPressCallback() --> Key Pressed:")
    disp(event.Key)

    if strcmp(event.Key, 's') % If the 's' key is pressed
        stopRotation = true; % Set stopRotation to true
         disp("s key-pressed simulation will stop...")
    end
end

% Function to draw the shape
function drawshape(matrix, colour)
    x = matrix(1,:);
    y = matrix(2,:);
    plot(x, y, colour, 'LineWidth', 2);
end

% Function to rotate the shape about a point (p,q) by angle a
function newShape = rotateabout(shape, p, q, a)
    % Translate shape to origin
    shape1 = translateShape(shape, -p, -q);
    % Rotate shape
    shape2 = rotateShape(shape1, a);
    % Translate shape back
    newShape = translateShape(shape2, p, q);
end

% Function to translate the shape
function newShape = translateShape(shape, xShift, yShift)
    x = shape(1,:) + xShift;
    y = shape(2,:) + yShift;
    newShape = [x; y];
end

% Function to rotate the shape
function newShape = rotateShape(shape, a)
    % Rotation matrix
    reflectMatrix = [cos(a) -sin(a); sin(a) cos(a)];
    % Apply rotation
    newShape = reflectMatrix * shape;
end

This code will create an animation of a fan with blades rotating. Pressing the 's' key during the animation will stop it. Note that the global stopRotation is used to allow the keyPressCallback function to modify the stopRotation variable. Make sure to execute the fan_animation() function to start the animation.

Note

Pressing the 's' key well stop the animation.

------------------------------------------------------------------------------------------------------------------------------------------------

If you find the solution helpful and it resolves your issue, it would be greatly appreciated if you could accept the answer. Also, leaving an upvote and a comment are also wonderful ways to provide feedback.

Professional Interests

• Technical Services and Consulting
• Embedded Systems
• Electrical and Electronics Engineering

[JIayun]

what is the use of global variables?thx

[Walter Roberson]

In your original code, stoprotation is local to the script, and local to the function keyPressCallback .

In order for the variable to be shared, you would have had to wrap a function around everything -- it is a limitation of MATLAB.

[JIayun]

thank you for your reply. what do you mean by shared?

[JIayun]

Can I take it that if there is no global varaible, if i pressed 's', stopRotation is assigned for true. but initially, stopRotation is assigned for false, the value for stopRotation is still unchange? Please correct me if my understanding is wrong.

[Hassaan]

@JIayun global keyword is used so that the same variable can be accessed or modified from different functions else the variable will be local

[JIayun]

we first declear global varaible in the main function, why do we need to declear again in keyPressCallback function

[Hassaan]

@JIayun In MATLAB, the global keyword is used to declare variables that are accessible in multiple function workspaces. If you declare a variable as global in one function, you must also declare it as global in any other function that intends to access or modify that variable. This is because each function in MATLAB has its own local workspace, and variables in one function are not accessible in another function unless they are explicitly declared as global.

[JIayun]

thank you very much. Another question is why do we need to set a fan_animation function

[Hassaan]

@JIayun fan_animation() is what actually implements the animation code loop. For your case think of it like a main() function having all the required function calling.

------------------------------------------------------------------------------------------------------------------------------------------------

If you find the solution helpful and it resolves your issue, it would be greatly appreciated if you could accept the answer. Also, leaving an upvote and a comment are also wonderful ways to provide feedback.

Professional Interests

• Technical Services and Consulting
• Embedded Systems
• Electrical and Electronics Engineering