I always have been derendering ugly stuff i dont want to see and avies I dont like. It´s an ossum feature! But be aware nowadays they made it permanent. Before it was temporary and I had to derender everytime i logged in again. If u want to render again and uses Phoenix or Firestorm:
As of the Phoenix 188.8.131.528 release we have changed the way Derender works. When you derender something now it is added to the assest blacklist. This allows you to permanently derender things.
Do NOT derender any of your alts, or they will not be able to log in correctly.
In layman’s terms, the asset blacklist is a shared resource. If you derender an alt, and subsequently try to log in with it, during login, Phoenix sees from the black list that this account should not be displayed, and so it doesn’t. You will find the account placed at 10, 10, 10, and likely unable to move.
To Derender an object right click on it → more → more → derender
To rerender it you need to remove it from the blacklist.
Access the Asset Blacklist from the Phoenix menu at the top of your screen.
Click on the item you want to rerender, note avatars show as objects.
Click the Remove button.
Change your group tag, or teleport out and back.
The object, or avatar will render in a few seconds.