add THREE.Mesh.prototype.containsPoint

[gonnavis]

example
mesh.containsPoint(new THREE.Vector3(0,0,0))

[mrdoob]

So the approach is so use a Raycaster and cast a ray from the point outside of the mesh (-z specifically), right?

What's your use case?

[gonnavis]

Hi mrdoob, I often need to change a mesh to point cloud, so I wrote the demo before.
The method is inspired by this answer, and I summerized to "Just raycast once from the point to any direction, then check the intersects num, if is odd, the point is in the geometry".
And found other people have the same demand, so I think if this method can embed into three.js will be very userful.
But I konw the performance is very bad, may be use gpgpu to speed up? I'll try.

[WestLangley]

If the mesh is not watertight -- e.g., a planar mesh, or a cylinder without end-caps, or TeapotBufferGeometry -- your approach will either not work, or will not be guaranteed to work. Correct?

[gonnavis]

Yes, may use some method to check if the mesh is watertight first?

[gonnavis]

Or use a option parameter, let the user to specify the direction, no-matter if the mesh is watertight, just use the direction to check.

[Mugen87]

I've never seen that an engine supports such a method in their Mesh class. AFAIK, at least Unity does not provide such a functionality. Probably because it's complicated to implement a generic containsPoint() method that reliably supports all types of meshes (like @WestLangley mentioned). I vote to keep such code on app level.

[WestLangley]

Right. This is an application-specific method, and it only works in certain cases.

See examples/js/utils/GeometryUtils.js for methods that will generate random points on the geometry surface.

[mrdoob]

Yeah, I can see this getting people confused when their model is not watertight. I'd prefer to add only robust methods to core. Better to leave this as application-specific.

Thanks though!