How to fill 2-D closed loops with lines? Boundary of this closed loops are extracted as output from slicing a STL file.

My main task is to slice STL file and generation of tool path into MATLAB for Laser metal deposition process.I have a list of polylines for each layer which I got after slicing a STL file in MATLAB. Now I have to develop the algorithm for filling these polygons using lines. I have to define the internal filling pattern for 2D closed-contour. so at the end I just want to fill this 2D closed loops with lines. IS there any functions, algorithms or opensource library for this work in MATLAB available? Each and every help will be appreciated as it is the first step of my new project.

[jonas]

Could you attach one of those contours and maybe a sketch of your desired output?

[yogi patel]

It would be any type of closed polygon.

[jonas]

And you want to fill it with lines, like this FEX function?

[yogi patel]

Please check attached figure..Thats how I want to fill it for finally generating tool path for robot code

[jonas]

Got it. Ill see if I can stitch something together using inpolygon.

[jonas]

So, problem resolved? Always appreciate some feedback after writing a piece of code.

[yogi patel]

I am really really thankful to you for this help. But as I am out of institute for few days didn’t get chance to try that and work on it.But I am damn sure that I will make my logic from this code. Once again thank you so much..will get back to you for further assist.?

[jonas]

I see! Please let me know if you run into trouble :)

Answer 1

[jonas]

I'm not one hundred percent certain this is exactly what you are looking for, but this algorithm does the following:

• Creates a hatched pattern on a surface with slope and distance between lines specified by k and m, respectively.
• Finds the line-segments inside of a specified polygons and plots those

Polygons with holes are a bit problematic, but I'm sure you can adapt this code to include also those.

% Define hatched pattern
f = @(m,k,x) m+k*x
m=-2:0.1:2; %Vert. distance between lines = .1
k=2; % Slope
x=0:0.001:1;
L=cell(length(m),1);
for i=1:length(m)
    L{i}=f(m(i),k,x);
end

% Define polygon
xp{1} = [.5 1 1 .5 .5]./2;
yp{1} = [.5 .5 1 1 .5]./2;
xp{2} = [.7 1 1 .7]-0.2;
yp{2} = [.7 .5 1 .7];

% Plot
ax = axes
hold on
ax.XLim=[0 1];
ax.YLim=[0 1];

% Draw polygon
cellfun(@(X,Y) plot(X,Y,'k'),xp,yp)

% Find points inside and draw those line segments
for i=1:length(xp)
  in = cellfun(@(y)inpolygon(x,y,xp{i},yp{i}),L,'uniformoutput',false)
  cellfun(@(Y,IN) plot(x(IN==true),Y(IN==true),'r'),L,in)
end

[Star Strider]

Impressive!

+1

[jonas]

Thanks :)

[yogi patel]

I am getting error like "not enough input argument" for this code line.

in = cellfun(@(y)inpolygon(x,y,xp{i},yp{i}),L,'uniformoutput',false);

Is it because of we didn't initialize value of y?

[jonas]

Impossible to say without seeing your code. You need to define a bunch of lines (stored in x and L) and some polygons (xp and yp).

[yogi patel]

I did not change the single line of code. Though it is showing some error in the line which I mentioned earlier. Error is regarding input arguments. Can you please run it one more time for checking purpose?

[jonas]

Oh, I made some extra break in a long line when I tried to formatted the code for posting it on the forum. Try again now and it should work fine :)

[yogi patel]

Thanks. That worked :) @jonas

[chao ye]

it is great，but How to fill multi connected region？

“Polygons with holes are a bit problematic, but I'm sure you can adapt this code to include also those.”