Hemesh substraction one with many works, but intersection does not.

Contributed Library Questions

p3tr4s

Hemesh substraction one with many works, but intersection does not.

in Contributed Library Questions • 16 days ago

Hi,

I am working with "Hemesh" Library intersection and substraction functions.

I have applied substraction, calculating not one element with another, but one with many.

Sadly, it works with substraction function, but for intersection, I miss something.

The substracted part is in blue color, and intersected part should be in red (but it does not work, but I either do not get any errors)

The code:

import wblut.math.*;
import wblut.processing.*;
import wblut.core.*;
import wblut.hemesh.*;
import wblut.geom.*;
import java.util.List;
WB_Render render;
void setup() {
size(1280, 720, OPENGL);
smooth();
//initialize WB_Render
render = new WB_Render(this);
}//setup
void draw() {
background(255);
//size of polygon, call it radius;
int dim = 200;
ArrayList <WB_Polygon2D> inputPolys = new ArrayList <WB_Polygon2D> ();
ArrayList <WB_Point2d> points = new ArrayList <WB_Point2d> ();
//Polygon a initialization (in this case triangle)
points.add(new WB_Point2d(width/2, height/3-dim));
points.add(new WB_Point2d(width/2+dim, height/2+dim/2));
points.add(new WB_Point2d(width/2-dim, height/2+dim/2));
inputPolys.add(new WB_Polygon2D (points));
///////////////////////////////////////////////////
//clear points or bad things would happen
points.clear();
//Polygon b initialization (in this case triangle)
points.add( new WB_Point2d(mouseX, mouseY-dim) );
points.add( new WB_Point2d(mouseX+dim, mouseY+dim/2) );
points.add( new WB_Point2d(mouseX-dim, mouseY+dim/2) );
inputPolys.add(new WB_Polygon2D (points));
///////////////////////////////////////////////////
points.clear();
//Polygon a initialization (in this case triangle)
points.add(new WB_Point2d(width/4, height/3-dim));
points.add(new WB_Point2d(width/5+dim, height/5+dim/2));
points.add(new WB_Point2d(width/5-dim, height/5+dim/2));
inputPolys.add(new WB_Polygon2D (points));
///////////////////////////////////////////////////
points.clear();
//Polygon a initialization (in this case triangle)
points.add(new WB_Point2d(width/4, height/3+dim));
points.add(new WB_Point2d(width/5-dim, height/8+dim/2));
points.add(new WB_Point2d(width/8+dim, height/5+dim/2));
inputPolys.add(new WB_Polygon2D (points));
////////////////////////////////////////////////////////////////////////substraction - blue color
List <WB_Polygon2D> subtractPolys = new ArrayList <WB_Polygon2D> ();
for (int i = 0; i < inputPolys.size(); i++) {
subtractPolys.addAll(subtractManyFromOne(inputPolys.get(i), inputPolys));
}
fill(0,0,255);
noStroke();
for (WB_Polygon2D p : subtractPolys) {
render.drawPolygon2D(p);
}
///////////////////////////////////////////////////////////////////////////intersection - red color
List <WB_Polygon2D> intersectPolys = new ArrayList <WB_Polygon2D> ();
for (int i = 0; i < inputPolys.size(); i++) {
intersectPolys.addAll(intersectManyFromOne(inputPolys.get(i), inputPolys));
}
fill(255,0,0);
for (WB_Polygon2D i : intersectPolys) {
fill(0);
render.drawPolygon2D(i);
}
noFill();
stroke(0);
// for (WB_Polygon2D p : inputPolys) {
// render.drawPolygon2D(p);
// }
}//draw
List <WB_Polygon2D> subtractManyFromOne(WB_Polygon2D one, List <WB_Polygon2D> many) {
List <WB_Polygon2D> allFragments=new ArrayList <WB_Polygon2D> ();// this will collect all the pieces that remain from "one" after subtracting "many"
allFragments.add(one); //start with the source poly "one"
for (WB_Polygon2D other:many) {
if (other!=one) {//this way "one" can be part an element of "many" and you don't have to worry about self-subtracting...
// Subtracting a polygon can result in several fragments.To subtract another polygon you need to do that for all fragments. Giving you a new list of
// fragments etc.
List <WB_Polygon2D> AllFragmentsMinusOther=new ArrayList <WB_Polygon2D> ();// this stores all new fragments
for (WB_Polygon2D fragment: allFragments) {
AllFragmentsMinusOther.addAll(WB_Polygon2D.subtract(fragment, other));
}
allFragments=AllFragmentsMinusOther;//for the next poly top subtract you need to start from the new list of fragments, etc.
}
}
return allFragments;
}
List <WB_Polygon2D> intersectManyFromOne(WB_Polygon2D one, List <WB_Polygon2D> many) {
List <WB_Polygon2D> allFragments=new ArrayList <WB_Polygon2D> ();// this will collect all the pieces that remain from "one" after intersecting "many"
allFragments.add(one); //start with the source poly "one"
for (WB_Polygon2D other:many) {
if (other!=one) {//this way "one" can be part an element of "many" and you don't have to worry about self-intersection...
// Intersecting a polygon can result in several fragments.To intersect another polygon you need to do that for all fragments. Giving you a new list of
// fragments etc.
List <WB_Polygon2D> AllFragmentsMinusOther=new ArrayList <WB_Polygon2D> ();// this stores all new fragments
for (WB_Polygon2D fragment: allFragments) {
AllFragmentsMinusOther.addAll(WB_Polygon2D.intersection(fragment, other));
}
allFragments=AllFragmentsMinusOther;//for the next poly top intersect you need to start from the new list of fragments, etc.
}
}
return allFragments;
}

Earlier, Amnon Owed gave me this script with intersections: But is it possible to make the upper script work with intersection "one with many"?

for (int i = 0; i < inputPolys.size(); i++) {
WB_Polygon2D a = inputPolys.get(i);
for (int j = i+1; j < inputPolys.size(); j++) {
WB_Polygon2D b = inputPolys.get(j);
List <WB_Polygon2D> polys = WB_Polygon2D.intersection(a, b);
for (WB_Polygon2D p : polys) {
fill(0, 50);
render.drawPolygon2D(p);
fill(0);
render.drawPolygon2DVertices(p, 5);
}//for

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