What's the Deal With Raytracing?

The companion article with this video:

Linus Tech Tips building a 16K display(!!!) using a 4x4 bank of 4k monitors:

[arohk]

Game Devs: Invest a huge amount of time to create realistic shadows and light effects.
Gamer: Turns off shadows for better fps.

[pigpuke]

Ray tracing isn't new, it's been around for decades. The reason why it seems new is because hardware is finally powerful enough to do it real time. I recall my dad playing around with ray tracing back in the early 1990's (it took over four hours to render a single scene at 320x200 in 8-bit colour albeit on a 80386). I realize that you (Mr. Young) probably know this, but some of your viewers (especially the younger ones) may not know this.

[aitch]

The thing that has me really excited about RTX tech is what they can do with audio path tracing. Real time dynamic reverb from moving sources, frequency modulation depending on the surface it's reflecting off of, distance muffling, sound transparency through different materials, doppler shifting, et cetera. In real life you take in so much auditory information that subconsciously builds the sense of space you're in, but we haven't had anything like that in video games until now. The idea hasn't gotten much press, but I think the effect is going to be much more profound for a sense of realism than most people would expect.



Though the RTX visuals in Control feel like a real milestone. I hadn't been so blown away by a game's effects in years as when I saw a running movie projector picked up and it kept casting the film wherever it pointed along with perfect shadows all in real time - shockingly incredible to see happen.

[mrmandolino]

Talking as someone who loves your written content, this is also great stuff. You have a knack for explaining stuff in a way that people without a technical background can easily follow your points

[diegofloor]

Doom 3 is ripe for the modding community to add raytracing.

[VOZmonsoon]

When he started excitedly listing off everything that was "free!" thanks to ray-tracing it sounded like he was trying to convert me to a new religion.

[QwertyCaesar]

Just came across this random video of Shamus' on shuffle. RIP, you were too young.

[GordonMaclachlan]

Oh Shamus it's more fair you are not here to witness the continuing development of this technology

[ingolifs]

It's interesting all the things you have to unlearn. Playing through Quake 2 RTX, I saw a glowing blue light on the gun of a grunt corpse, and noticed it was casting an almost imperceptible light on the ground. I also noticed the same of the glowing lights on the grenades. My first instinct was "Wow they've really thought of everything" but that's really not true. The game just does it. Also I instinctively wince when I come to an area I know will have lots of small lights, because I know multi-directional lighting is a resource hog on previous games. Nope, it treats all light and shadow the same, so it has no problem with a room full of diffuse light panels.

[KuraIthys]

Nothing new under the sun huh. I remember doing raytracing 30 years ago.

Granted, it took 5 hours to render a single frame of a very primitive scene...

But arguably raytracing as a concept might even be OLDER than the various tricks we've been using for 3d games in the last 30 years or so.

After all, Ray Tracing has always been a much closer approximation of the physics of light than all the weird bucket of rasterisation tricks.
I mean, Ray Tracing still does a few weird things - like trace from the camera outwards (where real light obviously comes from the light sources)

What I don't get is this 'graininess' stuff with modern 'raytracing'. To my knowledge that's not raytracing, but rather some variant technique (path tracing or whatever)

The thing is, Raytracing has two major flaws, which have plagued it from the start;
1. It is EXTREMELY slow. In the beginning this even made it difficult to use for pre-rendered sequences where you can justify using a render farm and taking hours to do a single frame. Realtime use was basically out of the question until about a decade ago, and even then it was only in very carefully crafted scenes and limited resolutions.
2. Raytracing (at least, the traditional formulation of it) can't do ambient lighting. AT ALL. Just flat out incapable of it. Thus, you have to combine raytracing with something else to get any ambient lighting effects. Or... Use a modified technique such as path tracing. If you see a tech demo calling itself 'raytracing', yet focusing on ambient lighting effects, I'd find that quite suspicious. Due to the slow performance of raytracing, the original solution was to just use an ambient colour value; which basically means the ambient lighting is handled the same as any rasterizer... Other options include combining it with Radiosity rendering, which happens to have the opposite problem - radiosity cannot really do specular lighting. Or, path tracing or similar extensions can be used, but that imposes new problems.

Speaking of new problems, the need to use denoising filters with 'Raytracing' solutions seems directly tied to the weakness of raytracing in doing ambient lighting.
The approach seems to be one of treating ambient lighting as a the sum/average of many specular lighting passes made with random reflection angles...
Seems a rather poor choice for it, but I guess they've settled on this method for a reason...

[SizzlingOne]

Glad to have found this channel. Really nice quick form of analysis. With retrospective elements to boot.

[mr_ako]

you forgot to say "it just works"

[sheridanglover]

9:41 No one told me this lecture was being given by a dracula. 0/10

[rickydo]

00:15 my graphics card is the one on the top right

[TheZetaKai]

Shamus Young died on Wednesday, June 15th, 2022, at 3am, of cardiac arrest. He is greatly missed by family, friends, colleagues, and his audience.

[cormano]

Thanks for the insights, Shamus. I used to watch your videos back in the day, so I'm happy to hear from you again. :)

[aaronmicalowe]

11:35 I like how when the character stands in front of the film projector, not only does she create a shadow on the wall, but the light that is blocked by her body is shown on her body. Not just the light, but the animated detail of the film. And all of this requires no additional programming as it's an emergent property of the raytracing algorithm.

[katemoody]

"the old way" to you, Shamus, isn't really the old way. I cut my gums on this stuff on the Amiga in the 90's with Imagine 3.0 (a raytracing program). It of course was not real time (an hour per 640x480 image of full raytrace rendering) but I always pined for a time when real time ray tracing could happen. It's early days, but I am glad it is starting to happen.

[NeovanGoth]

1:25 "It's been so long since I've seen something genuinely new" <- This is not exactly correct. Since the advent of programmable shaders, new rendering techniques (including raytracing) could be implemented in software instead of requiring explicit hardware support. The real increase was not found in the amount of pixels, but the amount of calculations per pixel. Also specialized raytracing hardware does _not_ add new features, it just accelerates certain operations used in raytracing to make it usable with decent performance without adding a ton of additional shader compute units.

[skaltura]

Dedicated hardware is not needed - just software support.
Minecraft raytraces on AMD hardware almost as good as on RTX :) That Neon Noir demo from Crytek ran Vega 56