Intersect does not seem to work when a shape is inside another

[aalexgabi]

const { polygon } = require('@flatten-js/core');
const { intersect } = require('@flatten-js/boolean-op');

const item1 = polygon([
  [0, 30],
  [30, 30],
  [30, 0],
  [0, 0],
  [0, 30],
]);

const item2 = polygon([
  [10, 20],
  [20, 20],
  [20, 10],
  [10, 10],
  [10, 20],
]);

const intersection = intersect(item1, item2);

console.log('item1', item1.svg());
console.log('item2', item2.svg());
console.log('intersection', intersection.svg());

Prints:

<path stroke="black" stroke-width="1" fill="lightcyan" fill-rule="evenodd" fill-opacity="1"   d="
M0,30 L30,30 L30,0 L0,0 L0,30 L0,30 z" >
</path>
item2 
<path stroke="black" stroke-width="1" fill="lightcyan" fill-rule="evenodd" fill-opacity="1"   d="
M10,20 L20,20 L20,10 L10,10 L10,20 L10,20 z" >
</path>
intersection 
<path stroke="black" stroke-width="1" fill="lightcyan" fill-rule="evenodd" fill-opacity="1"   d="" >
</path>

I also tried using the intersect method on the polygon object:

const { polygon } = require('@flatten-js/core');

const item1 = polygon([
  [0, 30],
  [30, 30],
  [30, 0],
  [0, 0],
  [0, 30],
]);

const item2 = polygon([
  [10, 20],
  [20, 20],
  [20, 10],
  [10, 10],
  [10, 20],
]);


console.log('item1', item1.svg());
console.log('item2', item2.svg());
console.log('intersection', item1.intersect(item2));

Which prints:

item1 
<path stroke="black" stroke-width="1" fill="lightcyan" fill-rule="evenodd" fill-opacity="1"   d="
M0,30 L30,30 L30,0 L0,0 L0,30 L0,30 z" >
</path>
item2 
<path stroke="black" stroke-width="1" fill="lightcyan" fill-rule="evenodd" fill-opacity="1"   d="
M10,20 L20,20 L20,10 L10,10 L10,20 L10,20 z" >
</path>
intersection []

[alexbol99]

Hello @aalexgabi ,

Indeed, this is a bug in boolean operations (very stupid), I will release a patch soon.

Method intersect of the polygon object returns array of intersection points between two boundaries, so in this case it returns empty array, which is normal.

By the way, when define polygon, don't need to repeat the first point, it cause obsolete zero-length segment in the path.

Thanks,
Alex Bol

[alexbol99]

Hello @aalexgabi ,

Bug fixed in @flatten-js/core package release v.1.2.5.
Note, that boolean operations now moved to core package under namespace BooleanOperations, you can use it like this:

  const { polygon } = Flatten;
  const { intersect } = Flatten.BooleanOperations;

  const item1 = polygon([[0, 30], [30, 30], [30, 0], [0, 0]]);
  const item2 = polygon([[10, 20], [20, 20], [20, 10], [10, 10]]);
  const intersection = intersect(item1, item2);

See how it works in this notebook.

Package @flatten-js/boolean-op not fixed yes

Best regards,
Alex Bol