How to animate flow particles like on windy

Question

Robert 2023-12-2

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https://ww2.mathworks.cn/matlabcentral/answers/2055504-how-to-animate-flow-particles-like-on-windy

回答： Avni Agrawal 2023-12-19

I am reposting this question from 2017. No real answer since. So let's try again.

Have a look at www.windy.com that animates wind speed and direction. Is there a way to generate an animation such as this for a given flow field in MATLAB?

Thanks

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Robert 2023-12-4

Right, however animatedline is very limited, you can't set alpha values to fade it out, you can't remove a set of points to make it look like it is moving. I guess the answer is no? there is no simple way to do this.

Dyuman Joshi 2023-12-4

编辑：Dyuman Joshi 2023-12-4

You can add quiver points on the animated line and adjust the properties accordingly. But I guess that would require a good amount of effort.

Does it have to be live animation (with some delay)?

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Answer 1

Avni Agrawal 2023-12-19

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在 MATLAB Online 中打开

Hi Robert,

I understand that you want to create a similar animation to that of www.windy.com in a particular direction. MATLAB provides several tools and functions that can be used to create animations similar to the wind speed and direction visualization seen on websites like www.windy.com. To animate a given flow field, you can use MATLAB's built-in functions such as ‘quiver’, ‘streamline’, or ‘streamribbon’ for visualizing vector fields, and then create an animation by updating the data in a loop and capturing frames for a video or GIF.

Here is a simple example of how to create an animation of a flow field using the ‘quiver’ function:

% Define the grid points where the flow field is computed 
[x, y] = meshgrid(0:0.2:10, 0:0.2:10); 
% Define the flow field (u and v are the velocity components in the x and y directions) 
% Here we use a simple example of a rotating flow field 
u = -y; 
v = x; 
% Create a figure window 
figure; 
% Number of frames in the animation 
numFrames = 120; 
% Preallocate the array for storing the frames 
frames(numFrames) = struct('cdata', [], 'colormap', []); 
% Loop to create each frame of the animation 
for k = 1:numFrames 
    % Update the flow field or any parameters for animation 
    u = -y * cos(k * 2 * pi / numFrames); 
    v = x * sin(k * 2 * pi / numFrames); 
    
    % Clear the axes for the new frame 
    cla; 
    
    % Plot the flow field using the quiver function 
    quiver(x, y, u, v); 
    
    % Set the axis limits 
    axis([0 10 0 10]); 
    
    % Capture the frame for the animation 
    frames(k) = getframe(gcf); 
end 
% Create an animation (video or GIF) 
% For a video: 
videoFile = VideoWriter('flowFieldAnimation.mp4', 'MPEG-4'); 
open(videoFile); 
writeVideo(videoFile, frames); 
close(videoFile); 
% For a GIF: 
% Use the imwrite function with 'DelayTime' and 'LoopCount' options in a loop 
% to write each frame to the GIF file.

In the example above, we create a simple rotating flow field and animate it over ‘numFrames’ frames. The ‘quiver’ function is used to plot the velocity vectors of the flow field. The ‘getframe’ function captures each frame, which can then be compiled into a video using MATLAB's ‘VideoWriter’ class or into a GIF using the ‘imwrite’ function.

Please refer to the following documentation page for more information on the ‘quiver’ function: https://www.mathworks.com/help/matlab/ref/quiver.html