How do I specify vertex normals on a mesh? - three.js

Question

I'm importing a mesh and have already computed the vertex normals for it. I want to use my normals instead of calling computeVertexNormals() for the geometry object. Right now I have
var geometry = THREE.Geometry();
// fill in vertex, face and texture
// ...
// compute normals
geometry.computeFaceNormals();
geometry.computeVertexNormals(); // <-- Would like to replace this
There is a reference in the docs to using a buffer attribute but no examples.
http://threejs.org/docs/index.html?q=vertex#Reference/Core/BufferAttribute
Does anyone know how to do this?
thanks,
john

Answer 1

In the case of a THREE.Geometry object the vertex normals are stored with the faces. If NormalList contains the normal vectors for the vertices then this loop will do it.
/*
* Add the normals. They are added to the face array
*/
for ( f = 0, fl = geometry.faces.length; f < fl; f ++ ) {
var face = geometry.faces[ f ];
var ndx = face.a;
var normal = new THREE.Vector3();
normal.x = NormalList[ndx].x;
normal.y = NormalList[ndx].y;
normal.z = NormalList[ndx].z;
face.vertexNormals[ 0 ] = normal;
ndx = face.b;
normal = new THREE.Vector3();
normal.x = NormalList[ndx].x;
normal.y = NormalList[ndx].y;
normal.z = NormalList[ndx].z;
face.vertexNormals[ 1 ] = normal;
ndx = face.c;
normal = new THREE.Vector3();
normal.x = NormalList[ndx].x;
normal.y = NormalList[ndx].y;
normal.z = NormalList[ndx].z;
face.vertexNormals[ 2 ] = normal;
}