Path Tracing vs. Ray Tracing, Explained


Posts: 92   +32
I used quite a bit of path tracing in Unreal and it has come a long way ... still we might be many years away for full pathtracing. Toughest problem is refraction, glass etc. There are a lot of cheats that we have to use to get glass, and translucency right. I think we might need 3 more generations of GPU hardware for detailed path tracing, and unfortunately we need the next gen consoles to have enough cores for it. At the same time the software side on engine level can give huge boosts. The main advantage of path tracing is that you could have dynamic building games where a player adds to the environment while things look as good as a prebaked illumination. You can have moving objects that illuminate the scene accurately. Destructible dynamic objects that cast shadows and lights correctly when they disappear. For game devs, nanites and path tracing is freedom, they can imagine more, they have less limitations, less focus on visuals cheats, more focus on creating things. Path tracing is the biggest thing that happened in games for quite a while. By they way I don't like Nvidia, AMD or Intel ... they are all corporate blood suckers.


Posts: 25   +19
They invented DLSS/FSR/XeSS exactly for this reason. You don't need a ludicrous 3090 to get good performance with RT enabled.

Such a shame that the GPU companies went down the wrong path and stuck with crappy ray tracing instead of developing accelerators for beam tracing. Rays are a 100% artificial construct, they are not light rays, they have zero physics embedded in them, and this is why we have to fudge things like colour, and we need hundreds of millions of rays to get a clean image. Beams on the other hand are actual solution of a simplified version of the actual Maxwell equations,called the Helmholtz equation. As such they carry all the physics with them: refraction, diffraction, refractive index, caustics, etc are all inherent in the beam. The equations for the beam tracing algorithm are similar to that required for rays, but more complex, but there are no fudges required. The big thing is you can get output with only a few hundred to a thousand beams, rather than millions of rays. You would just need to make the GPU's fp64 powerful. You don't need to solve the Helmholtz equation on the fly, just use beams that are solutions of the equation. I worked for Canon cameras and we developed a beam tracer to hopefully be used by the Canon lens design group. They were using the progam Code V as a test bed for their own design software, but it costs a bomb. Our relatively simple beam tracing program was benchmarked against Zeemax and could produce equal results to 10 million rays with 400 beams, but we could do things impossible with ray tracing. We could easily model things like vignetting, negative refractive index metmaterials, and colour of surfaces was naturally occuring by inclusion of the refractive index in the equations, even for metals which have complex refractive indices.

Beam tracing is a big deal in sonar and acoustics so disappointing to see us keep using ray tracing. Even Hollywood clings to this outdated technology.

Very interesting. Does sound an awful lot better than basic ray tracing alright. I did very basic classes in computer graphics 20+ years ago in college that covered ray tracing as it was at the time. Always would have liked to do more in this area, but never got chance (probably not smart enough anyway). Nvidia get some research and development in this please!

p.s I'm happy to hear someone charged Canon a bomb for something - a taste of their own medicine there considering how much they charge consumers for camera gear repair (eg 800+ for shutter replacement on EOS1D MKII for me years ago, similar amount for lens repair) ;-)


Posts: 418   +205
Well those images look amazing to me, but I wonder when can we really enjoy it without sacrificing fps or paying huge amount of money for high end GPUs ?

That day will come but in the mean time just save your money xD Sounds like a bad joke but well, anything can happen with new GPU generation 😉
I mean like with any new tech it always starts as something available only to the high end but without those users spending for and using said tech it doesn't ever get to become "mainstream"... If your lot in life says you need / should wait til it's basically commonplace well that's fine and expected for many but I do get tired of people telling me that it's "dumb" to support these things with hits to fps or buying expensive gpu's.

I'd much rather have the latest and greatest tech now and because I can afford it and don't mind the loss in performance (since I paid more for my gpu literally to make up for the hit and allow me access now).

It's only because of users like myself who want and push for this stuff to be included that people like yourself will eventually get to enjoy it.

Also DLSS has done a great job for me in every game I've played where I wanted to experience ray tracing by allowing me to basically get the fps I used to get without it but now with the heavy hit of adding RT.


Posts: 418   +205
The article shines light on an important topic but could have been clearer about the fact that what everyone calls raytracing in games today is actually path tracing. It would be easy for someone to assume that path tracing is coming to future games to “fix” current ray tracing troubles which isn’t true.

Ray tracing as implemented in current games already uses very few rays and is extremely biased about when and where those rays are cast. So it has none of the waste of the classic RT algorithm.

The article also implies that shading is necessary for rasterization but not RT. In reality rasterization and raytracing are just visibility queries. They both rely on (essentially the same) shaders to compute the actual texture and lighting of the geometry returned by those queries.

Yea where the confusion comes in (I believe) I'd that marketing has been calling what these gpu's are doing in most games as "ray tracing" while games like quake 2 rtx were marketed as "fully path traced" what was lost in the marketing hype is that the "ray tracing" we use now IS path tracing its just not "full path tracing" aka it still uses things OTHER than path tracing in addition to the (limited) path tracing the game is attempting.

This has led many (myself originally as well) to think that "path tracing" was harder than "ray tracing" and while that statement technically isn't true based on the terms most of us had identified each type of tech with it was.

It all just come down to the fact that "ray tracing" isn't actually ray tracing but like you said "path tracing" but typically with the help of other lighting tech (aka not "full path tracing")


Posts: 418   +205
Yeah, raytracing and later pathtracing are definitely the future, though we are still probably like 2-3 generations away from making less intensive raytracing viable without big FPS sacrifice. Pathtracing will likely take quite a bit more of time to be viable. Still interesting tech and it truly does help making atmosphere in those older games better. Sure original graphics got their charm, but still, so does raytracing. Plus I do hope they try to eventually use raytracing to do something new in games that will eventually just require it, so it won't have to be this very optional thing they out on the top for few percent. But fir now it will just remain RTX on for screenshots, RTX off for playing. :-D
See even Seth here has the terms confused and is making that same mistake I mentioned directly above this post.

What we call "ray tracing" in most games today isn't ACTUALLY ray tracing... It's a basic path tracing tech and the tech Seth refers to as "path tracing" is likley him referring to the situation we see in games like quake 2 rtx aka "full path tracing" (meaning no additional help from alternative solutions amd ALL lighting is handled by the path tracer)

Actual ray tracing as described above is SIGNIFICANTLY more impact on performance than path tracing and we don't in fact have any games using real ray tracing they just choose to call it that for marketing purposes.
Ray tracing is 15-20fps
Path tracing is 3-5fps

"path tracing, the fast cousin of ray tracing. Looks almost as good, works a heck of a lot quicker."
... Reverse your fps values above. Ray tracing is significantly more expensive than path tracing.


Posts: 1,237   +1,190
I think the industry is heading the wrong direction.

One, I feel nothing bad about the original screenshots above. In fact they are even better than the 'traced ones.

Two, you are not watching a screensaver to admire all the graphics while you are frantically running with your guns around. Especially in multiplayer games, where you are constantly being hounded and targeted.

Three, the cost of a capable card that can play these games smoothly with tracing set to on is just too much, when without tracing, even modest cards can run these games comfortably.
Even if the price comes down, there's still the above two issues.

For me, like the folding phone craze, these ray tracing BS is just a novelty marketing gimmick, especially for the suckers who defend it.
I'm really curious where these generational improvement s are. When you use Nvidia's modern game comparisons the 4080 16 GB is about 20-25% faster than 3090 Ti. When u take the core count multiplied by the MHz increase. U get a 23% increase. Sooo ??. Why not buy a 3090ti with more ram for cheaper. The 16gb 4080 is 1200$. If u can OC a 3090 to to 2250 u can even that out. Obviously the 4080 16 GB will OC more but reference or cheap cards probably won't OC much or u don't have the PSU to do it. The cards that do OC will cost 1300-1400. How does Nvidia expect to win this when a 6950 with half the cores of a 3090 Ti is keeping up or winning if u can get it to 2600-2800 MHz. All the new games will be based on rDNA 2 or 3. If they don't have any generational gains how will they beat a 13k core and GPU that clocks to 3.2-3.5 with enough infinity cache for 4k. Why are we even talking about dlss or far when we have the power to it at native. Who the hell even owns a super high refresh rate 4k screen. And if u do both Nvidia and AMD's new cards should do it at 120-144 hz. So u need any more?