Two THREE.BoxGeometry intersect error.

[kxh4892636]

The example code is as follows.

import { BoxGeometry, BufferGeometry, PlaneGeometry } from 'three'
import { Brush, Evaluator, INTERSECTION } from 'three-bvh-csg'

const intersection = (
  geometry1: BufferGeometry,
  geometry2: BufferGeometry,
): BufferGeometry => {
  const brush1 = new Brush(geometry1)
  const brush2 = new Brush(geometry2)

  const csgEvaluator = new Evaluator()
  const result = csgEvaluator.evaluate(brush1, brush2, INTERSECTION)

  return result.geometry
}

const geo1 = new BoxGeometry(10, 10, 10)
const geo2 = new PlaneGeometry(10, 10)
geo2.translate(0, 0, 5)
const geo3 = new BoxGeometry(10, 10, 10)
geo3.translate(0, 0, 10)

const intersection1 = intersection(geo1, geo2)
const intersection2 = intersection(geo1, geo3)
console.log(intersection1.getAttribute('position'))
console.log(intersection2.getAttribute('position'))

The bottom surface of geo3 is the same as geo2, but when the two BoxGeometry intersect, the result is null. However, when BoxGeometry intersects with PlaneGeometry, the result is correct.

The result is as follows.

BufferAttribute {
  isBufferAttribute: true,
  name: '',
  array: Float32Array(18) [
    -5, 5,  5, -5, -5, 5,  5,
     5, 5, -5, -5,  5, 5, -5,
     5, 5,  5,  5
  ],
  itemSize: 3,
  count: 6,
  normalized: false,
  usage: 35044,
  updateRange: { offset: 0, count: -1 },
  gpuType: 1015,
  version: 1
}
BufferAttribute {
  isBufferAttribute: true,
  name: '',
  array: Float32Array(0) [],
  itemSize: 3,
  count: 0,
  normalized: false,
  usage: 35044,
  updateRange: { offset: 0, count: -1 },
  gpuType: 1015,
  version: 1
}

[gkjohnson]

Please provide a live example with something like jsfiddle and pictures of the issue

[kxh4892636]

I create the live example, the link as follow.

The bottom surface of geo3 is the same as geo2. geo1 and geo3 have no intersection (but the intersection should be a surface), while geo1 and geo2 have the correct intersection result. You can see the intersecting results in the console.

https://codesandbox.io/s/kind-wave-3jmvks

[gkjohnson]

Again - please provide pictures and explain what you expect. If you look at this there's nothing incorrect about the result. The result of an intersection of two shapes in a just-touch configuration has no volume and therefore no shape.

However, when BoxGeometry intersects with PlaneGeometry, the result is correct.

Using PlaneGeometry is not valid since it is not two manifold and has no volume.