Hmmm, precomputing lighting clearly works and works well for static lights.
Where RT lights come in are:
1. Less work from the developer
2. Less precompiling
3. Dynamic and/or moving lights can become possible (including reflected lights off of moving surfaces).
Those are the things that were demonstrated with the extra-shiny Stormtrooper demo (
).
It certainly adds an element of realism. But at the same time, there's an element of over-realism. Because we've never seen dynamic lighting in video games before, such demos are overemphasizing them... kinda like how "Wizard of Oz" overemphasized the cartoony colors of color-TV back when color-TV became a thing.
We will need a few generations of video games before we see "realism". For now, we'll see overly shiny cars and overly-shiny helmets that don't really have a realistic atmosphere. Until the artists figure out to use raytracing correctly anyway... I really find a lot of the recent demos to be ridiculous.
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The best lighting is lighting that you
don't notice. Lighting that sets the mood, provides contrast, and draws the eye towards the important elements of the screen. Lighting doesn't necessarily have to be "realistic". Lightning just has to set the mood correctly.
See Pulp Fiction:
The light is
behind Samuel Jackson's afro, a very unrealistic position when you consider what is going on in the room. But the lighting draws your attention to the scene (the guns, the faces, etc. etc.) while drawing your eye away from the background. That's cinematography right there: not necessarily being "realistic", but using lights to accomplish a goal... a way for the director to communicate with their audience.
A "realistic" light setup for that room would be dimly lit from only the window in the background. Its clear that the room doesn't have any lights in it, so why can we clearly see their faces? Well, that's cinematography done right. It doesn't worry about the details, its #1 goal is communication with the audience. Realism be damned.
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Video Game lighting gets better and better, and more realistic. But video game directors still don't know how to use lighting to communicate well. At some point, we have to recognize that its the video game art direction that's a problem as opposed to technology.