# Exclude child from PShape to create mask is it possible?

**URL:** <https://discourse.processing.org/t/exclude-child-from-pshape-to-create-mask-is-it-possible/10425>\
**Category:** Coding Questions\
**Created:** [April 18, 2019, 1:39pm UTC](https://discourse.processing.org/t/exclude-child-from-pshape-to-create-mask-is-it-possible/10425 "2019-04-18T13:39:32Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![Stanlepunk](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/stanlepunk/32/11509_2.png) [@Stanlepunk](https://discourse.processing.org/u/Stanlepunk)\
**Post date:** [April 18, 2019, 1:39pm UTC](https://discourse.processing.org/t/exclude-child-from-pshape-to-create-mask-is-it-possible/10425/1 "2019-04-18T13:39:32Z")

</div>

I try to create a donnut with `PShape`, but this mission is more difficult than I think, I I don’t find a methode like `pshape.exclude(group_a)` or `pshape.remove(group_a)` or something like that there is a way do to that?

```auto
PVector [] pts_a;
PVector [] pts_b;
PShape s;
PShape group_a;
PShape group_b;
void setup() {
  size(300,300);
  generate_mask();
}

void draw() {
  background(255);
  s.fill(255,0,0);
  s.noStroke();
  shape(s);
}

void keyPressed() {
  generate_mask();
}

void generate_mask() {
  pts_a = new PVector[4];
  pts_a[0] = new PVector(0,0);
  pts_a[1] = new PVector(width,0);
  pts_a[2] = new PVector(width,height);
  pts_a[3] = new PVector(0,height);
  
  pts_b = new PVector[4];
  for(int i = 0 ; i < pts_b.length ; i++) {
    pts_b[i] = new PVector(random(width),random(height));
  }
  s = createShape(GROUP);
  group_a = createShape();
  group_b = createShape();
   
  group_a.beginShape();
  for(int i = 0 ; i < pts_a.length ; i++) {
    group_a.vertex(pts_a[i].x,pts_a[i].y);
  }
  group_a.endShape(CLOSE);
  
  group_b.beginShape();
  for(int i = 0 ; i < pts_b.length ; i++) {
    group_b.vertex(pts_b[i].x,pts_b[i].y);
  }
  group_b.endShape(CLOSE);
  
  s.addChild(group_a);
  s.addChild(group_b);
}

```

the result expected is something like that :  
 ![mask](https://canada1.discourse-cdn.com/flex036/uploads/processingfoundation1/original/2X/2/22b5db5d7aa0c72bf841cb69e4b8aa9b41aab0fa.jpeg)  
And if it’s possible with PShape my second step is to code that without PShape only with vertex with my proper class, but I’m lock on the first step ☹

---

<div class="post-metadata">

**Author:** ![solub](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/solub/32/333_2.png) [@solub](https://discourse.processing.org/u/solub)\
**Post date:** [April 18, 2019, 2:54pm UTC](https://discourse.processing.org/t/exclude-child-from-pshape-to-create-mask-is-it-possible/10425/2 "2019-04-18T14:54:18Z")

</div>

Hi @Stanlepunk,

Not sure to fully understand your issue, could the `beginContour()` [method](https://processing.org/reference/PShape_beginContour_.html) be a solution to your problem ?

---

<div class="post-metadata">

**Author:** ![Stanlepunk](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/stanlepunk/32/11509_2.png) [@Stanlepunk](https://discourse.processing.org/u/Stanlepunk)\
**Post date:** [April 18, 2019, 3:29pm UTC](https://discourse.processing.org/t/exclude-child-from-pshape-to-create-mask-is-it-possible/10425/3 "2019-04-18T15:29:17Z")

</div>

Sorry for my cheapr english and explication. Your solution is on the way what i need, but the behavior is very weird, my purpose is see the background on the delimited zony by the four points.

```auto
PVector [] pts_ext;
PVector [] pts_int;
PShape s;

void setup() {
  size(300,300);
  generate_mask();
}

void draw() {
  background(255);
  // fill(255,0,0);
  // noStroke();
  shape(s);

  stroke(0);
  strokeWeight(10);
  for(int i = 0 ; i < pts_int.length ; i++) {
    point(pts_int[i].x,pts_int[i].y);
  }
}

void keyPressed() {
  generate_mask();
}

void generate_mask() {
  pts_ext = new PVector[4];
  pts_ext[0] = new PVector(0,0);
  pts_ext[1] = new PVector(width,0);
  pts_ext[2] = new PVector(width,height);
  pts_ext[3] = new PVector(0,height);
  
  pts_int = new PVector[4];
  int marge = 50;
  pts_int[0] = new PVector(marge,marge);
  pts_int[1] = new PVector(width-marge,marge);
  pts_int[2] = new PVector(width-marge,height-marge);
  pts_int[3] = new PVector(marge,height-marge);
  s = createShape(); 
  s.beginShape();
  s.fill(255,0,0);
  s.strokeWeight(1);
  s.stroke(0);
  for(int i = 0 ; i < pts_ext.length ; i++) {
    s.vertex(pts_ext[i].x,pts_ext[i].y);
  }
  // s.vertex(pts_ext[0].x,pts_ext[0].y);
  
  s.beginContour();
  for(int i = 0 ; i < pts_int.length ; i++) {
    s.vertex(pts_int[i].x,pts_int[i].y);
  }
  s.vertex(pts_int[0].x,pts_int[0].y);
  s.endContour();
  
  s.endShape(CLOSE);
}

```

 ![11](https://canada1.discourse-cdn.com/flex036/uploads/processingfoundation1/original/2X/1/12f14f46c8fe13a7cf4a90eb736b1ab97636b9ce.png)

---

<div class="post-metadata">

**Author:** ![solub](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/solub/32/333_2.png) [@solub](https://discourse.processing.org/u/solub)\
**Post date:** [April 18, 2019, 4:23pm UTC](https://discourse.processing.org/t/exclude-child-from-pshape-to-create-mask-is-it-possible/10425/4 "2019-04-18T16:23:13Z")

</div>

Interesting, it looks like [there is a bug](https://forum.processing.org/two/discussion/22275/what-am-i-doing-wrong-with-my-pshape-contour) in `PShape.beginContour()`.

According to @jeremydouglass’s answer the solution is to create a shape without calling the `PShape` method.

```auto
def setup():
    size(100, 100)
    
    background(52)
    translate(width/2, height/2)

    beginShape()
    noStroke()

    vertex(-50,-50)
    vertex(50,-50)
    vertex(50,50)
    vertex(-50,50)

    beginContour()
    vertex(-20,-20)
    vertex(-20,20)
    vertex(20,20)
    vertex(20, -20)
    endContour()

    endShape(CLOSE)

```

PS: don’t forget that “the exterior shape and the interior contour **must**  **_wind_ in opposite directions**.”. In your code the vertices of your interior contour should go in counterclockwise order (pts\_int[0], pts\_int[3], pts\_int[2], pts\_int[1]).

---

<div class="post-metadata">

**Author:** ![jeremydouglass](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/jeremydouglass/32/20_2.png) [@jeremydouglass](https://discourse.processing.org/u/jeremydouglass)\
**Post date:** [April 18, 2019, 5:21pm UTC](https://discourse.processing.org/t/exclude-child-from-pshape-to-create-mask-is-it-possible/10425/5 "2019-04-18T17:21:52Z")

</div>

That is right – for more discussion of this open bug, see:

> <https://github.com/processing/processing/issues/4978>

---

<div class="post-metadata">

**Author:** ![Stanlepunk](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/stanlepunk/32/11509_2.png) [@Stanlepunk](https://discourse.processing.org/u/Stanlepunk)\
**Post date:** [April 19, 2019, 9:30am UTC](https://discourse.processing.org/t/exclude-child-from-pshape-to-create-mask-is-it-possible/10425/6 "2019-04-19T09:30:05Z")

</div>

I try to find a way to fix the bug, but it’s too complex for methe relation between `PShape`, `PGraphics` and `PGraphicsJava2D`… ☹ That may be one of the reasons why in Processing 4 project it’s write :

```auto
Improve or replace PShape

    PShape has grown very complex and should probably be handled differently.
    When started, we were looking for a lightweight (a few Kb) way to do SVG. Nowadays, size footprint isn't much of an issue, so it might be better to get improved support by using something like Batik underneath.

```