The goal of the ShadowOnlyMaterial is to display only shadows casted by a light on a receiving object. It is mostly useful when you want to display shadow on a transparent canvas (on top of your existing DOM).
ShadowOnly material can be found here: https://github.com/BabylonJS/Babylon.js/blob/master/dist/preview release/materialsLibrary/babylon.shadowOnlyMaterial.js
A demo can be found here: http://babylonjs-playground.com/#OBGRK#31 -
ShadowOnly material is dead simple to use. Just apply it as material to any mesh where you want to display only shadow:
var ground = BABYLON.Mesh.CreatePlane('ground', 1000, scene) ground.rotation.x = Math.PI / 2 ground.material = new BABYLON.ShadowOnlyMaterial('shadowOnly', scene) ground.receiveShadows = true
Limitation: Please note that only the first light that can reach the mesh will be used. So if you have multiple lights in your scene you may end up using