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Index › Programming Questions & Help › Programs › Shape() with hole

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Shape() with hole (Read 617 times)

alphachapmtl

Shape() with hole
Aug 15^th, 2007, 9:24pm

This will fill a 2D polygonal shape, the 2nd overlapping the 1st:

fill(somecolor,somealpha);
beginShape();
vertex(10,10);vertex(5,10);vertex(5,5);vertex(10,5);
endShape(CLOSE);fill(somecolor,somealpha);
beginShape();
vertex(20,20);vertex(0,20);vertex(0,0);vertex(20,0);
endShape(CLOSE);

Can I fill a shape with a hole ? without filling the hole ?
I mean fill the 2nd polygon without overlapping the polygonal hole?

Of course it "can" be done, but can it be done simply ?
using only the ..Shape() methods ?

Any suggestion ? Thanks, alphachapmtl

(if you email me, I can send you a .png image showing polygonal rings I need to fill)

fry YaBB Moderator Offline Posts: 2623 mass, usa	Re: Shape() with hole Reply #1 - Aug 15^th, 2007, 10:54pm there's currently no built-in means for doing it using the main API. you might try a way to hack around it, or use a library (geomerative might support this).

alphachapmtl Full Member Offline Posts: 128 Canada	Re: Shape() with hole Reply #2 - Aug 16^th, 2007, 8:03pm Can I cut/copy/paste a polygonal region ? That way I could save the hole and restore it later.

alphachapmtl

Re: Shape() with hole
Reply #3 - Aug 19^th, 2007, 12:08pm

The following message from <JohnG> gives a solution:

One possible way is to pick a vertex on the outer poly, and then find the closest vertex on the inner, and use that as an invisible break.. so you just draw one poly, like so:

Draw from "outside break" vertex around the outside back to itself, but instead of ending there, then draw the inside one, and go around that, in the opposite direction, back to the inside break, and then the last vertex is the outside break again.

This test program shows an example:

//polygonhole1
//2007-aug-17
//alphachapmtl

int x0,y0;

void setup() {
size(900,400);
background(0);

// square_cyclic
x0=width/6;
y0=height/2;
for (int i=0;i<8;i++) {
int delta=20*i;
stroke(0,0,200,50);
fill(200,0,0,50);
beginShape();//cyclic order
vertex(x0-delta, y0-delta);
vertex(x0-delta, y0+delta);
vertex(x0+delta, y0+delta);
vertex(x0+delta, y0-delta);
endShape(CLOSE);
}//for

// square_cyclic + insquare_cyclic
x0=3*width/6;
y0=height/2;
for (int i=0;i<8;i++) {
int delta=20*i;
stroke(0,0,200,50);
fill(200,0,0,50);
beginShape();//cyclic order
vertex(x0-delta, y0-delta);
vertex(x0-delta, y0+delta);
vertex(x0+delta, y0+delta);
vertex(x0+delta, y0-delta);
vertex(x0-delta, y0-delta);
if (i>0) {//cyclic order
int deltaOld=delta-20;
vertex(x0-deltaOld, y0-deltaOld);
vertex(x0-deltaOld, y0+deltaOld);
vertex(x0+deltaOld, y0+deltaOld);
vertex(x0+deltaOld, y0-deltaOld);
vertex(x0-deltaOld, y0-deltaOld);
vertex(x0-delta, y0-delta);
}
endShape();
}//for

// square_cyclic + insquare_anticyclic >> THIS WORKS !!
x0=5*width/6;
y0=height/2;
for (int i=0;i<8;i++) {
int delta=20*i;
stroke(0,0,200,50);
fill(200,0,0,50);
beginShape();//cyclic order
vertex(x0-delta, y0-delta);
vertex(x0-delta, y0+delta);
vertex(x0+delta, y0+delta);
vertex(x0+delta, y0-delta);
vertex(x0-delta, y0-delta);
if (i>0) {//anticyclic order
int deltaOld=delta-20;
vertex(x0-deltaOld, y0-deltaOld);
vertex(x0+deltaOld, y0-deltaOld);
vertex(x0+deltaOld, y0+deltaOld);
vertex(x0-deltaOld, y0+deltaOld);
vertex(x0-deltaOld, y0-deltaOld);
vertex(x0-delta, y0-delta);
}
endShape();
}//for

exit();
}

void draw() {
}

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