RAY TRACING and other RENDERING METHODS

in a lot of my videos I say that software doesn't matter it is you and the knowledge about the software that matters today we're going deep gentlemen after this video you will understand how the magic behind your renders works fun [Music] [Applause] the more you know about these deep processes the more control you have over everything over the look of your 3d scene and more importantly over the time it takes to render your 3d scene first in my talk about render engines I briefly mentioned the light in photography and cinematography is briefly get back to that topic photos and videos a result of our camera recording light humans have an ultimate sensor called eyes that's why the light is the most important aspect and it defines the look they feel the quality of your photos and videos I have a big light source on my right the race this light emits are scattered across my room and reflected by other objects I have here each ray from this light source gets bounced billions of times before it gets to my camera sensor and gets recorded you can imagine how many rays are there in this room right now bouncing trillions of times this is why real life looks so good good models textures materials eternal variety of elements and enormous amount of light bounces captured by our eyes or camera one of the most popular topics is the hardware we use in our work and it makes sense because opposed to real world computers have limits of what they can calculate in real life eyes are capturing uncountable amount of data non-stop computers are far away from that kind of processing power and clever people came up with the different rendering methods there are several rendering method rasterization ray casting ray tracing and path tracing there are also subgroups for these but we won't go that deep let's start with the restoration this is what was possible in the beginning of computer era and it is what all computer games are using till this day this method doesn't use any race it simply helps to display geometry on your screen basically rasterization takes vector data and transforms it into pixels it refers to both primitives like polygons and 3d models to make it simpler 3d model consists of polygons polygons are formed with points points are placed in space using different math 3d scenes are using XYZ coordinates remember geometry is cool but your screen is flat to the XY plane for example here is our camera imagine that this is our screen with pixels in it the rasterizer takes the points from every polygon and calculates where to put them on screen then it's processing the space between the points and turns the shape into a group of pixels after all polygons are processed the computer is able to show you that 2d representation of your 3d object rasterization is what our 3d softwares are using to display our scene in the viewport and it's still the most popular way of producing 3d graphics in real time it is extremely fast because it's simply a process of transforming our scene geometry into pixels this doesn't really sound like actual rendering does it indeed looking at your scene in a viewport is also a rendering method the second method back in a days when computers just appeared was rendering using ray casting I prepared a 3d scene that will help me to demonstrate everything the rays are casted from the camera one through every pixel when the objects in the scene are intersected by the Ray the computer records the closest point to the camera and its color value that can be determined from a texture let's say we want our image to be thousand by thousand pixels resolution this means the computer have to cast 1 million race each ray calculation is tens if not hundreds of lines of code to process I think you guessed how challenging it was back to 70s a massive amount of calculations for the computers to do this method also limits everything creatively as it's only a texture that defines the color of geometry as the Rays going one direction only it means no reflections or shadows possible does that remind you something this flat look started to change in 1980 when a man called Turner Whitted turned Ray casting into something different something revolutionary previously witted made researches for a nuclear power industry and he was studying the behavior of light photons in space so this clever man knew exactly how light behaves in real life let's look at our sample 3d scene again with it introduced what we know as Ray bounces the ray tracing method with this method the computer is also sending a ray through every pixel but when the Ray hits an object instead of recording the data straight away the computer sends more rays one to each light source from this intersection point to find out how these lights are affecting the color or brightness of this point the point could now have shading an illumination data calculated if that ray did meet another geometry on its way to light source it means there is something blocking the light and our intersection point should be darker as it lies in the shadow if the object was reflective the computer sent a new ray forward at a certain angle to check if there is another object which should be reflected in our intersection point and so on until the ray meets a light source this was revolutionary because artists could finally art direct the scene they could dictate the behavior of the race by setting up the materials a material dictates how light should be reflected or maybe it's absorbed or maybe the light goes through the material there are billions of these bounces drawing our scene appearance over the years this method got modified and improved but still it wasn't a simulation of reality these calculations simulated only a reflection refraction and hard shadows hard shadows because the light and this method is a point in space which rays are travelling to get soft shadows who have to cheat to get global illumination we have to cheat and so on it was a huge jump towards a photorealistic renders that we are familiar with nowadays though ray tracing has been promised for years as a ultimate gaming experience but even today's computers are too slow for this method to be calculated at 60fps technology is constantly evolving and what we see in real-time renders nowadays is truly impressive just this year we have seen the Star Wars real-time ray tracing them or released by Unreal Engine and was powered by NVIDIA sir RTX technology still required a computer which costs fifty thousand dollars to run at 24 frames per second but it is a perfect example of how realistic real-time rendering can be with good skills and time spent on cheating ray tracing is good for everything including now real time engines but what about let's say VFX where image has to be flawless in order to be believable there is a purely offline rendering method that is not suitable for real-time engines just yet due to calculations needed and it's called path tracing once again it sounds raised through pixels but when the ray hits an object instead of tracing new race to the points of light sources it keeps bouncing the same ray between scene objects as many times as necessary to get to light source this allows to gather information about the objects that are close to each other find out what color they are and if that color effects the previous object in simple words the Rays are acting like light in a real world this is why the path racing engines care about size of the light not the position because every individual ray can hit a surface of their life it is no longer restricted to a point you will have your soft shadows calculated properly in color bleeding like let's say if colored object is intensely lit caustics like fancy light reflections through the bottle nowadays GPUs are getting more and more advanced powering path tracing engines and you can add many GPUs in one system more than processors this means you can render realistic scenes in the matter of seconds but everything always depends on a lot of factors for instance I'm waiting for octane for to be ready for production use because they're introducing the the noise system noise in path tracing render engines is one of the most painful topics and looks like octane for eliminated that problem but this is a topic for another video how does it feel now when you know exactly what's going on behind your renders and how they are born if you guys still have questions feel free to use comment section thumbs up if that lecture was interesting to you subscribe if CG and VFX is something you're into thanks for watching guys see you soon peace [Music]

Channel: Andrey Lebrov

Views: 226,557

Keywords: lebrov, cg, vfx, tutorial, how to, learning, filmmaking, step up, master, rendering, rasterizer, ray tracing, path tracing, ray casting, turner whitted, light rays, explained, render methods, RTX, RTX 2018, RTX2080, real time ray tracing, optix, denoising

Id: LAsnQoBUG4Q

Length: 10min 22sec (622 seconds)

Published: Tue Jul 31 2018

Reddit Comments

[u/mahatma_arium_nine]

So path tracing is the method closest to how light bounces off of objects but its not available in real time rendering due to the massive number of calculations necessary.

So 2080 AD then?

[u/Nightblade]

What's that fucking glowy thing on the shelf?

[u/CammKelly]

The key with these is accuracy, you don't need to calculate everything in the environment, nor do you need to calculate every bounce. With good engine support, I can't see either being that far off, but much like you don't run SSAA at max, neither will you be running RT or PT at max for a while, if ever.

[u/experts_never_lie]

Ray tracing is a useful step, but it won't be the end state. In the end, you'll want to solve the full illumination equation, and that requires at least a radiosity model. With ray tracing, the interplay between colors of surfaces and their mutual illumination isn't captured. This (standard graphics pipeline) vs. ray tracing vs. radiosity trade-off has been going on for over 20 years. It won't end until the highest quality is so cheap that no one considers anything else … if that ever occurs.

[u/Charuru]

Oh this is you? Nice!

[u/NV_Tim]

To get an idea of the modern history of Ray Tracing we posted a Dev blog about it. It's written by J. Turner Whitted who helped outline the modern foundation for RT. It doesn't touch on path tracing, but gives some direct "I was there" insight into RT and the research that goes into bringing these ideas from concept to commodity.

[u/[deleted]]

Interesting. Thank you!

[u/Chuppyzocker]

Do you actually know if NVidia will work on their Mental Ray or if they switch to working on Optix for Arnold?