void Mesh_normalize( Mesh *myself )
{
    Vert     *vert = myself->vert;
    Triangle *face = myself->face;

    for( int i=0; i<myself->mNumVerts; i++ ) vert[i].normal = vec3(0.0f);

    for( int i=0; i<myself->mNumFaces; i++ )
    {
        const int ia = face[i].v[0];
        const int ib = face[i].v[1];
        const int ic = face[i].v[2];

        const vec3 e1 = vert[ia].pos - vert[ib].pos;
        const vec3 e2 = vert[ic].pos - vert[ib].pos;
        const vec3 no = cross( e1, e2 );

        vert[ia].normal += no;
        vert[ib].normal += no;
        vert[ic].normal += no;
    }

    for( i=0; i<myself->mNumVerts; i++ ) verts[i].normal = normalize( verts[i].normal );
}