The NGLE Manual
Invisible Ledges
by George
Maciver
Remember the ledges in TR3 that you can only
see when Lara lights a flare, or if a flame reveals them?
Well, you can have 'em! Make your ledges between rooms as
normal and light your rooms.
When that's done texture your ledges on all sides, including
top and bottom, with doublesided and transparent on. At this
stage the ledges will show because of the room lighting.
Now place an effects lightbulb on all six faces of your
ledge (all the sides and top and bottom) but instead of
increasing the effects bulb lighting, decrease it to a minus
value until you get the right result (this may take some
tweaking).
In game the ledges will be invisible, but a flare or flame
will illuminate them as invisible blocks just as in TR3.

Tinnos Revisited by Kitkat