How to add a texture to one side of a cube without THREE.MultiMaterial to reduce draw calls - three.js

Question

So lets say theres a cube with 2 materials.I'm using MultiMaterial but maybe thats not the correct approach because its showing 6 draw calls instead of 2. I'm worried about performance when it scales up.
http://codepen.io/glued/pen/JXmvzm
This is just an example, I know about FaceColors but would like to mix a meshBasicMaterial with another Material, say, with a texture.
var greenMaterial = new THREE.MeshBasicMaterial({ color: 0xc4f288 })
var orangeMaterial = new THREE.MeshBasicMaterial({ color: 0xf4511e })
var mats = [
orangeMaterial,
greenMaterial,
orangeMaterial,
orangeMaterial,
greenMaterial,
orangeMaterial
]
let box = new THREE.Mesh(geometry, new THREE.MultiMaterial( mats ))
If i used vertexColors: FaceColors and a texture:
new MeshBasicMaterial({ vertexColors: FaceColors, map:someTexture }))
how would i designate the texture for a specific face only?

Answer 1

I figured it out by creating a material with a texture and removing the UVs on the geometry faces that i'm not using
the texture is 128x256, See the codepen as i'm using a 2d canvas to generate
texture.repeat.y = 0.5
texture.offset.y = 0.5
let geometry = new THREE.BoxGeometry(50, 50, 50)
function assignUvAndColor(geo, i, color = 0x00cbff){
geo.faceVertexUvs[0][i] = new Array(3).fill(new THREE.Vector2(0, -1))
geo.faces[i].color.setHex(color)
}
const greenColor = 0xacffd3
assignUvAndColor(geometry, 3, greenColor)
assignUvAndColor(geometry, 2, greenColor)
assignUvAndColor(geometry, 0, greenColor)
assignUvAndColor(geometry, 1, greenColor)
assignUvAndColor(geometry, 4)
assignUvAndColor(geometry, 5)
assignUvAndColor(geometry, 6)
assignUvAndColor(geometry, 7)
let material = new THREE.MeshBasicMaterial({ map: texture, vertexColors: THREE.FaceColors })
let box = new THREE.Mesh(geometry, material)
http://codepen.io/glued/pen/grBEmo?editors=0010

Answer 2

multimaterial will always do N drawcalls where N = length of its material array
(see renderer implementation)
it does not even try to check whether some of its materials are duplicite in reference - so in your examples you have multimaterial with 6 materials = 6 drawcalls
you will have to change the geometry face material index or abandon using multimaterial and divide your geometry manually