This is a Runelite plugin which enables a (janky) first-person perspective. There are two modes, the detached camera mode, and the GPU rendering mode.
By default this plugin makes use of the Occulus mode of camera, you will be unable to interact with any NPCs or Objects whilst the plugin is on.
Alternatively, you can make use of the 'GPU rendering' config setting. This will instead draw the scene entirely from scratch.
This REQUIRES either the GPU plugin or the 117HD plugin to be active to work.
HOWEVER, this will not adjust any other Runelite plugins and their overlays, meaning they will not align with your view.
Additionally, clickboxes will act as though you camera were at the usual position, not positioned in your head. So although you can interact with things, it's far from easy to.