Ray Tracing, How difficult is it to do?

[Psychosis]

Take an old game, be it on Unreal Engine or a different one.

How difficult and what would be necessary to turn off shadows and lighting and add your own?

Given that the game is old and doesn't have many items\vertices it may be possible to add a form of Ray Tracing or other Global Illumination and have it perform well.

Why has no one did it before?

Games that are on my mind:

dishonored
portal prelude
Bioshock 1,2
Dark Souls
Witcher
Freelancer
Mafia
Half Life 1,2
Far Cry
Max Payne
Fear
C&C Renegade
Dead Space
Burnout Paradise


Edit:

Found this http://gamasutra.com/blogs/AlexandruVoi ... _games.php



This is how your existing, rasterized-only game engine used to look



Meet your new game engine with added ray tracing: improved shadows, better transparency and reflections



Current Alpha Blending transparency technique



Ray-Traced transparency

[ENBSeries]

You have no idea how slow raytracing is and how to complex to implement and optimize it. It's heavily depends on memory speed and latency, which is already bottleneck for gpu/cpu. Even the best examples of raytrace converted games running at low fps, low resolutions, have very low world detail and definetly they don't have shadows from all lights, reflections from everything and other pop bullshit.