How to get the normal of a face in a plane (not a vertice)

[elkyu]

Hi,

 

Yes, me again ...

 

So, I still have my plane with some face (triangle) compose by 3 vertex.

 

I can get the face ID, get the 3 vertex which compose a face, get the normal of each vertex but now, I would like to find how to get the normal of a face (not the all plane, just one face) ..

 

I try with the function getNormal() (pickingInformation) but each time that return x=0 y=1 z=0, but some face are inverted and the function return the same result I don't know why

[jahow]

Hey again,

 

This is where it's done in the BJS code (used for converting mesh to flat shaded): https://github.com/BabylonJS/Babylon.js/blob/master/src/Mesh/babylon.mesh.ts#L1102

 

Basically the normal of a face is the cross product of two of its three sides, but you have to compute it yourself (this data is not stored, unlike vertices normals).

 

Good luck

[elkyu]

Thank you ! It's done and it's working

 var positions = plane.getVerticesData(BABYLON.VertexBuffer.PositionKind);scene.onPointerDown = function(evt, pickResult){                               if(pickResult.hit){                    faceId = pickResult.faceId;                    var vertex1 = BABYLON.Vector3.FromArray(positions, indices[faceId * 3] * 3);                    var vertex2 = BABYLON.Vector3.FromArray(positions, indices[faceId * 3 + 1] * 3);                    var vertex3 = BABYLON.Vector3.FromArray(positions, indices[faceId * 3 + 2] * 3);                    var p1p2 = vertex1.subtract(vertex2);                    var p3p2 = vertex3.subtract(vertex2);                    var normal = BABYLON.Vector3.Normalize(BABYLON.Vector3.Cross(p1p2, p3p2));                }}

[GameMonetize]

You can also call pickResult.getNormal()

[elkyu]

You can also call pickResult.getNormal()

 

Like I said, it's not working . Each time that return x=0 y=1 z=0 , but some face are inverted ..

[jahow]

That's because this method uses the vertices normals to compute the face normal: https://github.com/BabylonJS/Babylon.js/blob/master/src/Collisions/babylon.pickingInfo.ts#L21

 

The difference between both type of computations should probably be documented somewhere...

[GameMonetize]

Correct

[GameMonetize]

I updated pickingInfo.getNormal to allow both versions:

getNormal(useWorldCoordinates = false, useVerticesNormals = true)

[MinsuKim]

On 2015. 7. 2. at 오전 12시 48분, Deltakosh said:

두 버전 모두 허용하도록 pickingInfo.getNormal을 업데이트했습니다.

getNormal (useWorldCoordinates = false, useVerticesNormals = true)

this code is work for me!!

[jerome]

http://doc.babylonjs.com/how_to/how_to_use_facetdata

getFacetNormal()