three.jsvertexnormalsface

Three.js: Convert face normal from local space to world space

I have a THREE.PlaneGeometry, with ComputeFaceNormals(). I create two meshes using this geometry, with different rotations applied to them. I want to compute the two angles between the camera and the two meshes central face normal. It should be :

vLocalCamera = vCamera.position - mesh1.position;

mesh1.normal() . vLocalCamera = cos(angle);

The problem is that I don't know how to get the mesh normal in world coordinate (from geometry and mesh rotation) with three.js API

Solution

  • If you want to convert a face or vertex normal, normal, from local space to world space, you do it like so:

    var normalMatrix = new THREE.Matrix3(); // create once and reuse
var worldNormal = new THREE.Vector3(); // create once and reuse

...

normalMatrix.getNormalMatrix( object.matrixWorld );

worldNormal.copy( normal ).applyMatrix3( normalMatrix ).normalize();

    three.js r.107