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Index › Programming Questions & Help › OpenGL and 3D Libraries › 2d shape subtraction

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2d shape subtraction (Read 1803 times)

sam_mcelhinney

2d shape subtraction
May 14^th, 2010, 4:25pm

is there an equivalent of this:

Code:

size(400,400);
fill(255);
stroke(0);

beginShape();
// outer shape
vertex(100,100);
vertex(300,100);
vertex(300,300);
vertex(100,300);
vertex(100,100);  

breakShape();
//cutout
vertex(150,150);
vertex(150,250);
vertex(250,250);
vertex(250,150);
endShape(CLOSE);

that works with OPENGL rendering?

S

martin_p

Re: 2d shape subtraction
Reply #1 - May 15^th, 2010, 12:02am

Are thinking about creating a menger sponge perchance If so it has been done before see-
http://www.openprocessing.org/visuals/?visualID=8332
for a recent version or check out the processing archive for a version by Tom Carden. I hadn't even come across the 2D breakshape before seeing your post, but I don't think there is 3D version.

And here is were to find the the real answer, don't you check the documentation/discourse This only the start of the thread make sure you read FRY's answer.
No wonder I hadn't heard of it before!!!

Cedric wrote on Dec 16^th, 2009, 10:01am:

This question was asked several times the last few days and i always give the same answer.
I know breakshape is not documented yet but works pretty good most of the times. So maybe we can add it to the reference page.

it was first mentioned by davebollinger on his flickr account :
http://www.flickr.com/photos/davebollinger/3598281488/

sam_mcelhinney

Re: 2d shape subtraction
Reply #2 - May 15^th, 2010, 2:22am

no, I do read the discourse Martin; hence I asked if there was an equivalent

and also no, that's not what i'm trying to do, either.
i'm trying to draw an isovist in 2d plan for a set field of view. a bit like this: http://www.lydiaheard.com/citywalker/assets_c/2008/10/compact_isovist1.html
but restricted to a 60 span and changing in realtime as the viewers moves.

I figure the simplest way to do this is to calculate the full 60 degree view cone and the subtract the 'shadow' shapes of any objects in the way. Hence my query.

If this has been done before in processing, i'd love to see it, but I can't find anything.
S

sam_mcelhinney YaBB Newbies Offline Posts: 34	Re: 2d shape subtraction Reply #3 - May 15^th, 2010, 9:29am ok dynamic isovist constructed; but using a different method after all. see here for details: http://dl.dropbox.com/u/6460407/_00_ISOVIST.zip S

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