MATLAB: Draw filled triangle and possibly change aspect ratio

aspect ratiodrawtriangle

How can I draw a filled equilateral triangle (actually white) with background black? I don't want to have any x and y axis on the drawing. I just need the graph.

And also how can I define an aspect ratio (hight:width) of the triangle and then get the different triangles of different aspect ratio from an equilateral triangle?

I think some logic for the length of pixels should work but I could not figure out.

Thanks in adavance!!

Best Answer

Hi Chen,

As mentioned by Rik, you can use patch command to draw the triangles and set axes properties to get desired results. Below mentioned code will help you draw triangles with specified aspect ratio:

w=10; %width of triangle
ar=0.866; % Aspect ratio for equilateral triangle
h=ar*w;%height of triangle
x=[0 w w/2];%x coordinates of vertices
y=[0 0 h];%y coordinates of vertices
patch(x,y,'white') %plotting triangle in white color
set(gca,'Color','k','xticklabel',[],'yticklabel',[])%setting background black and removing labels
daspect([1 1 1]);%equal data unit length along x and y axis
xlim([-5 15])
ylim([-5 15])

You can tweak above code to get required geometry for the triangle.

Kindly refer this documentation link to know more details on using ‘patch’ command.

Hope this helps!

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MATLAB: How to create triangle and animate it

Try this

w0 = 1 ;
w1 = 0.5 ;
N = 5 ;
ww = linspace(w1,w0,N) ;
W = [fliplr(ww) ww] ;
ar=0.866; % Aspect ratio for equilateral triangle
h=ar*W;%height of triangle
fig = figure();
ax = axes();
set(ax,'Color','k','xticklabel',[],'yticklabel',[])
ax.XLim = [0 1];
ax.YLim = [0 1];
p = patch([0 0 0], [0 0 0], 'w');
for i = 1:length(W)
    
    x = [0 W(i) W(i)/2];%x coordinates of vertices
    y = [0 0 h(i)];%y coordinates of vertices
    
    p.Vertices = [x.' y.'];
    
    drawnow
    pause(0.1)
    
end

MATLAB: How to create randomly distributed triangles

Slightly editing your code gets me to a max framerate of just under 200. Results will vary for different systems.

w = 3 ;
ar=0.866; % Aspect ratio for equilateral triangle
h=ar*w;%height of triangle
p=[];origins=cell(1,10);
figure(1),clf(1)
for k=1:10
    x=[0 w w/2];%x coordinates of vertices
    y=[0 0 h];%y coordinates of vertices
    x=x+15*rand-5;y=y+15*rand-5;%add random
    p(k)= patch(x,y,'white'); %#ok<SAGROW> plotting triangle in white color
    origins{k}=[mean(x) mean(y) 0];%store explicitly to prevent having to retrieve it from an object
end
set(gca,'Color','k','xticklabel',[],'yticklabel',[])%setting background black and removing labels
daspect([1 1 1]);%equal data unit length along x and y axis
xlim([-5 15]),ylim([-5 15])
rotation_per_frame_in_deg=0.8;
target_fps=60;
frametime=1/target_fps;
h_tic=tic;
for n=1:60%do 60 frames
    tic
    for k=1:numel(p)
        rotate(p(k),[0 0 1],rotation_per_frame_in_deg,origins{k})
    end
    drawnow
    pause(frametime-toc)%comment this line to see the max framerate
end
t=toc(h_tic);
fprintf('the fps was %.1f Hz\n',n/t)

Best Answer

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