How to use Three.js plane

Question

I'm trying to use three.js plane to get the distance from a point to a plane.

I have three points a,b,c, that I calculate the normal like so:

    const v = a.clone().sub(c);
    const u = b.clone().sub(c);
    const normal = u.cross(v);

Then

const plane = new THREE.Plane(normal, (?))

What are you supposed to give in the second argument?

From the docs:

the negative distance from the origin to the plane along the normal vector. Default is 0.

What does that mean?

If I place there the distance of one of the points a,b,c to (0,0,0) (positive and negative distance), like const dist = a.distanceTo(new THREE.Vector3(0,0,0)), then if I do:

plane.distanceToPoint(a);

I'm getting a huge number and not zero, the same happens if I leave that argument empty.

So how can I place that plane at its correct place so that the distance to points on that plane will be zero as it should?

why not to use `.setFromCoplanarPoints(a, b, c)` method of `THREE.Plane()` as you already have three coplanar points? — prisoner849, Aug 07 '17 at 09:48
I didn't see that function in the docs, I'll try. @prisoner849 — shinzou, Aug 07 '17 at 09:50
@prisoner849 yes it looks a lot better now, thanks. You can write this as the answer. — shinzou, Aug 07 '17 at 09:58
@kuhaku [This change](https://github.com/mrdoob/three.js/commit/efccbfee0d27bf44503454d3d9f292b76a243f3e) has not made it into production yet, but it should clarify things for you. — WestLangley, Aug 07 '17 at 10:43
It should clarify that it's just the distance from (0,0,0), "origin" and "signed" can be confusing. @WestLangley — shinzou, Aug 07 '17 at 10:52

score 0 · Accepted Answer · answered Aug 07 '17 at 10:04

0

As you have three coplanar points, you can use .setFromCoplanarPoints(a, b, c) method of THREE.Plane().

An example of using it is in this SO answer.

answered Aug 07 '17 at 10:04

prisoner849

16,894
4
34
68

How to use Three.js plane

1 Answers1