Feast your eyes upon these beautiful
images. Oh my goodness. And get this, none of them are real. None. Yes, that’s right. These images were created through a technique
called ray tracing. Simulating the paths of light rays to create beautiful images and animations.
And, goodness, it would be an absolute dream to be able to create video games that look like
this. So, wait, why is not everything ray traced today? Well, there is a problem, and not a
small one. And this problem is noise. Look. What is going on here? Well, during this process,
we have to shoot millions and millions of light rays into the scene to estimate how much light
is bouncing around, and before we have simulated enough rays, the inaccuracies in our estimations
show up as noise in these images. Do not worry, this clears up over time as we simulate more rays,
but it may take from minutes to days for this to happen, even for a smaller scene. For instance,
in an earlier paper, this one took us 3 full weeks to finish. 3 weeks! Yes, really. I am not
kidding. Ouch. So, can we do this in real time? Here is a classical technique, path tracing
trying to create images in quick succession for real-time applications. Whoa! This
is a terrible disappointment. As you see, there is unfortunately plenty of noise here. But
wait, noise filtering techniques exist that are specifically designed for light transport,
and these do an absolutely amazing work, look at how much more we know about this scene.
But still, but come on…if you look at this, who would be able to guess what
the real image should be? No one. Now, wait a second, we have decades of research
works in the area of ray tracing, so if we jump in time about 30 years, we get this. This is
so much better, however, this is unfortunately, still not that usable. So, is that it? Is all hope
lost for getting these beautiful ray-traced images in real time? Well, don’t despair, despite
the fact, that unfortunately, the problem gets even worse. Dear Fellow Scholars, this is
Two Minute Papers with Dr. Károly Zsolnai-Fehér. How does it get worse? Well, as soon as you
start moving the camera, we get this thing that we call high-frequency noise that makes
almost all of this footage completely unusable, even after noise filtering. There
is just too much flickering. And now, hold on to your papers, because here
is this absolutely miraculous new paper that can do this instead. This is a collaboration
between University of Utah and NVIDIA and it not only looks so much better immediately,
wow! However, it has four more huge advantages that only reveal themselves to experienced
Scholars with a keen eye. One, try to look at the frequency of the noise. It is of much
lower frequency, in other words, it is a great deal less jumpy so when we hand it over to the
denoiser, it can do so much better with it. Two, it also has much better antialiasing. What
does that mean? Well, look - the edges are more visible, better resolved. Once again,
that is a lot more helpful for the denoiser. Three, it is able to get more information
out of each light path that we simulate. How much more? Well, 25 times more. Yes,
these results are equivalent to 25 times more rays with previous techniques, that
is a huge leap in capabilities. And, four, large glowing light sources that
are not in focus, called bokeh, seem to be often completely gone with
the previous methods for quite a while, but are resolved better with this technique. I
am absolutely stunned by these results. So good! Now, despite all this, not even this
technique is perfect. Three things here. One, we don’t yet know how well it generalizes to
motion blur, things getting a little blurry when we move objects or the camera around.
Two, if we need a super sharp still image and we are willing to wait for longer, there are
some moving parts called pixel filters that this does not do well with. This is not super
relevant for real-time applications. Three, it takes a tiny bit more time per frame than
previous techniques, but it is totally worth it. And there are more good news. The source code
of this project is also available. They just give this out to all of us free of charge.
Absolutely amazing. When I was a PhD student, I was thinking whether real time ray tracing will
be a possibility in my lifetime, and here we are, approximately 10 years later, and we get this. I
can’t believe it. What a time to be alive! Make sure to have a look at the paper in the video
description, it is beautifully written. Also, I have a master-level course on light transport
that is completely free for everyone, no strings attached. We write a full light simulation
program from scratch there, check it out!
