Partial invisibility effect

Partial invisibility is an effect which appears when the player picks up a blur artifact or when we see a partially invisible thing. The thing retains its shape, but instead of color we see black pixels scattered randomly (applied by colormapping the pixels behind it to darker shades), which makes the thing more difficult to see. Partial invisibility is applied to Spectre by default.

In Heretic, Hexen, and some source ports, partial invisibility is achieved by translucency (using the TINTTAB color map).