three.js – How can I dynamically change object’s opacity?

THREE.MeshLambertMaterial extends THREE.Material which means it inherits the opacity property, so all you need to do is access the material on your object, and change the opacity of the material:

object.materials[0].opacity = 1 + Math.sin(new Date().getTime() * .0025);//or any other value you like

Also note that the material must have it’s transparent property set to true.

object.materials[0].transparent = true;

(Thank you Drew and Dois for pointing this out)

Update

the property is now simply material:

// enable transparency
object.material.transparent = true;
// set opacity to 50%
object.material.opacity = 0.5;