Three.js: PlaneHelper is error at some point

[whatisor]

Description of the problem

PlaneHelper is error at some point.
Please take a look at this, during scanning, PlaneHelper will be in a wrong direction.
https://codepen.io/karoshi/pen/MPEJeG/
I looked at updateMatrixWorld function, and see this:
this.lookAt( this.plane.normal );
It seems a bug of lookAt function usage.

Three.js version

• [ ] Dev
• [x] r97
• [ ] ...

Browser

• [x] All of them
• [ ] Chrome
• [ ] Firefox
• [ ] Internet Explorer

OS

• [x] All of them
• [ ] Windows
• [ ] macOS
• [ ] Linux
• [ ] Android
• [ ] iOS

Hardware Requirements (graphics card, VR Device, ...)

[WestLangley]

PlaneHelper.position should not be changed from ( 0, 0, 0 ). It was not designed for that.

[Mugen87]

I think you should use a mesh with an instance of PlaneBufferGeometry in order to visualize your scanner. PlaneHelper is intended to visualize an instance of Plane which represents a flat, 2D surface that extends infinitely far. The second parameter size only exists to avoid visual clutter when rendering the helper.

[WestLangley]

@Mugen87 PlaneHelper is designed to visualize a clipping plane. Be careful not to clip the helper, however.

localPlane = new THREE.Plane( new THREE.Vector3( 1.0, 0, 0 ), - 1 );
renderer.localClippingEnabled = true;
material.clippingPlanes = [ localPlane ];

var helper = new THREE.PlaneHelper( localPlane, 20, 0x0000ff );
scene.add( helper );

//

localPlane.constant -= speed; // animate

[Mugen87]

PlaneHelper is designed to visualize a clipping plane.

If this is its actual purpose, you should call it ClippingPlaneHelper.

[WestLangley]

If this is its actual purpose, you should call it ClippingPlaneHelper.

Its purpose is to render a Plane. A clipping plane is a special case.

Neither should Box3Helper be renamed to BoundingBoxHelper.

[whatisor]

if its pupose is "Its purpose is to render a Plane", I think this still need to be fixed. Because Plane is plane, not only 0 position plane :)

[whatisor]

Do you have some idea why lookAt failed? I have no idea of reason...

[WestLangley]

@whatisor Please see the Plane docs and make sure you understand Hessian Normal Form. Please use the forum if you need more help.

[whatisor]

I know the solution. We should create update(plane) API which is consistency with BoxHelper design :)

[WestLangley]

@whatisor See https://threejs.org/examples/webgl_clipping_intersection.html.

[whatisor]

That means it refers to the original plane, do not need to call an update.