Three.js png texture - alpha renders as white instead as transparent - three.js

Question

I'm creating a cube and I apply 6 different textures to each of it's faces. Each texture is a .png file and contains transparent parts. I'm also applying a color to the cube - I want to see that color trough png transparency.
Problem: Transparency renders as white color so I cannot see the base color of the cube (which renders ok if I remove the png texture)
How can I make the png transparency work? I tried playing with some material settings but none make it transparent.
Code for creating the cube and materials:
var geometry = new THREE.CubeGeometry(150, 200, 150, 2, 2, 2);
var materials = [];
// create textures array for all cube sides
for (var i = 1; i < 7; i++) {
var img = new Image();
img.src = 'img/s' + i + '.png';
var tex = new THREE.Texture(img);
img.tex = tex;
img.onload = function () {
this.tex.needsUpdate = true;
};
var mat = new THREE.MeshBasicMaterial({color: 0x00ff00, map: tex, transparent: true, overdraw: true });
materials.push(mat);
}
cube = new THREE.Mesh(geometry, new THREE.MeshFaceMaterial(materials));
cube.position.y = 150;
scene.add(cube);
EDIT:
Picture below shows the problem - with senthanal solution the left texture now renders ok - it is a png image without transparency - I set the transparency in code with
materialArray.push(new THREE.MeshBasicMaterial({ map: THREE.ImageUtils.loadTexture('img/s2.png'), transparent: true, opacity: 0.9, color: 0xFF0000 }));
The right texture is also a png image - only that it has a transparent area (all that renders white should be pure red since it is transparent and should take the color from the cube?). How can I make that white part transparent?

Answer 1

the opacity attribute of material does the trick for you. Follows, example code snippet:
var materialArray = [];
materialArray.push(new THREE.MeshBasicMaterial( { map: THREE.ImageUtils.loadTexture( 'images/xpos.png' ), transparent: true, opacity: 0.5, color: 0xFF0000 }));
materialArray.push(new THREE.MeshBasicMaterial( { map: THREE.ImageUtils.loadTexture( 'images/xneg.png' ), transparent: true, opacity: 0.5, color: 0xFF0000 }));
materialArray.push(new THREE.MeshBasicMaterial( { map: THREE.ImageUtils.loadTexture( 'images/ypos.png' ), transparent: true, opacity: 0.5, color: 0xFF0000 }));
materialArray.push(new THREE.MeshBasicMaterial( { map: THREE.ImageUtils.loadTexture( 'images/yneg.png' ), transparent: true, opacity: 0.5, color: 0xFF0000 }));
materialArray.push(new THREE.MeshBasicMaterial( { map: THREE.ImageUtils.loadTexture( 'images/zpos.png' ), transparent: true, opacity: 0.5, color: 0xFF0000 }));
materialArray.push(new THREE.MeshBasicMaterial( { map: THREE.ImageUtils.loadTexture( 'images/zneg.png' ), transparent: true, opacity: 0.5, color: 0xFF0000 }));
var MovingCubeMat = new THREE.MeshFaceMaterial(materialArray);
var MovingCubeGeom = new THREE.CubeGeometry( 50, 50, 50, 1, 1, 1, materialArray );
MovingCube = new THREE.Mesh( MovingCubeGeom, MovingCubeMat );
MovingCube.position.set(0, 25.1, 0);
scene.add( MovingCube );
http://threejs.org/docs/#Reference/Materials/Material The key is to set transparent attribute true and set opacity to 0.5(for example).
Add the second the cube which fits inside exactly with no transparency, idea from #WestLangley ( Three.js canvas render and transparency )
backCube = new THREE.Mesh( MovingCubeGeom, new THREE.MeshBasicMaterial( { color: 0xFF0000 }) );
backCube.position.set(0, 25.1, 0);
backCube.scale.set( 0.99, 0.99, 0.99 );
scene.add( backCube );

Answer 2

for those looking for a simple transparent png import helper:
import { MeshBasicMaterial, TextureLoader } from 'three'
export const importTexture = async(url, material) => {
const loader = new TextureLoader()
const texture = await loader.loadAsync(url)
material.map = texture
material.transparent = true
material.needsUpdate = true
return texture
}
//usage
const geo = new PlaneGeometry(1, 1)
const mat = new MeshBasicMaterial()
const mesh = new Mesh(geo, mat)
scene.add(mesh)
//this is asynchronous
importTexture('path/to/texture.png', mat)