Draw a box with triangles in three.js

make-a-box.js

// the box geometry to initialise
var box=new THREE.Geometry();

// the trick to make all faces: vectors i, j and k have the coordinates of the triangles in the box
var i="011010111111100101000000001011110100".split('').map(c=>(c=='0')?0:1),
    j="000000011010111111100101011010011010".split('').map(c=>(c=='0')?0:1),
    k="001011001011001011001011000000111111".split('').map(c=>(c=='0')?0:1);

// this function multiplies each of the coordinates by a transformation matrix that turns them
// into an arbitrary box
i.map(function(v,n){
    var vec=MRI.multMatVec(mat,[i[n],j[n],k[n]]);
    box.vertices.push(newVector(vec))
});

// faces are added to the box
for(l=0;l<12;l++)
    box.faces.push(new THREE.Face3(l*3,l*3+1,l*3+2));
var material=new THREE.MeshBasicMaterial({wireframe:true});

// the final object is added to the scene
mesh=new THREE.Mesh(box,material);
scene.add(mesh);