Updated Glow Effect

Garry hated the L4D-looking glow effect that we had with the engine, so I rewrote it inspired by our Facepunch.Highlight mesh outline effect, it outputs to HDR so the glow itself comes naturally from the intensity of the outline really helping it pop out.

The whole effect is highly configurable, you can set if it's additive, opaque, and it's depth aware now, both visible and occluded parts of the glow can be changed, so for example, items that are being held by the physgun are partially visible when occluded.

To have the previous behaviour you only need to make both visible and occluded parts share the same parameters.

You can get really creative with this effect, playing with it allows creators to make something unexpected, if you are doing a Predator/Zombie-style gamemode you can easily use it to have a sort of wallhack vision for example.