this is not the best example but are you talking about volumetric stuff?
That requires ray marching.
In case it could help, we have a volumetric fog material plugin:
PGDemo | Babylon.js Playground (babylonjs.com)
This may be close to the effect you want.
Do you mean something like this:
It does seem like this, but your demo is only suitable for a solid color background. You are using a color to cover the model, but it does not actually become transparent
This demo covers the model with a color and is not suitable for transparent situations
You can make a material instead:
Thank you, this is exactly the effect I want