karylo

Point to Plane question

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My question has to do with how to generate a vector from a point to the nearest point on a plane.  If I have a mesh moving inside a box, I want to know the distance and direction from the mesh position to each side of the box.  I understand that would be a vector perpendicular to the plane that intersects the point.

Does Babylon have a method that will do that for me?  TIA

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Hiya K! 

Um... I have some quick thoughts.  Imagine that your box is made from 6 planes, positioned to form a box shape.  Then...

distance = BABYLON.Vector3.distance(mesh.position, oneWallOfTheBox.position);

and direction... umm... you get that by... umm...

direction = mesh.position.subtract(oneWallOfTheBox.position)   // I think.  Or maybe it's...

direction = oneWallOfTheBox.position.subtract(mesh.position)  // not sure.

How to determine which is the nearest wall of all 6?  I dunno.  Perhaps, whenever mesh is moved, you need to check .distance() on all 6 box walls.  The lowest distance as the nearest wall.  ??  hmm.

I think there may be fancier and/or easier ways to attain these values.  Let's listen for more/better replies.  Using a "ray" (similar to a picking ray)... might give you direction and distance all in one little piece of code, but I am not a ray master.

https://www.babylonjs-playground.com/#12D0ST#1

There is some "ray" activities happening in the line 62 area.  Not sure about the story, there.  It looks as-if SOMEBODY almost knew what they were doing, though.  :)

That PG was found via a playground search for 'distance'.

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Planes have normals, which are perpendicular, so you can work from there backwards (computeWorldMatrix updates everything, if you move the planes around).
The normal, if you are inside a box will probably be facing outwards, so you may not need to .negate() the Vector3 as I did.
http://playground.babylonjs.com/#QZH25V

If you don't want to write any math, you can use rays like in the PG.  Otherwise the normal of a plane can be calculated as the Cross from subtracting the corners (see comment in PG).

https://en.wikipedia.org/wiki/Normal_(geometry)

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