How does Ray Tracing Work in Video Games and Movies?

Summary

This video delves into the intricacies of Ray Tracing, a technology pivotal for creating realistic CGI in movies and TV shows. It explains how path tracing, the industry standard, simulates light interactions to render scenes with lifelike quality. Despite its computational intensity, recent advancements in GPU architecture have made real-time rendering feasible. The video also explores Ray Tracing's application in video games, contrasting methods like path tracing with screen space ray tracing, and highlights the educational resources available for those interested in the field.

Takeaways

• 🌟 Ray Tracing is a rendering technique used in TV shows and movies to create realistic images by simulating how light interacts with 3D models.
• 🚀 The industry standard for rendering realistic scenes is path tracing, which requires an immense number of calculations.
• 💡 Path tracing was considered computationally impossible for decades due to its high computational demands, but advancements in technology have made it feasible.
• 🎬 Movies like Zootopia, Moana, Finding Dory, and Coco were rendered using path tracing, which required thousands of computers and multiple months to complete.
• 🧩 Ray Tracing works by sending rays from a virtual camera through a view plane and into a scene, calculating how light bounces off objects to create realistic lighting and shadows.
• 🖼️ Each pixel in a rendered image is determined by numerous rays, with each ray potentially bouncing multiple times off different surfaces before reaching the camera.
• 📊 Direct illumination is calculated by sending shadow rays from the point of intersection to each light source to determine the brightness of a pixel.
• 🔄 Indirect illumination is calculated by bouncing secondary rays off surfaces to simulate light reflecting from one object to another, contributing to global illumination.
• 💻 The bounding volume hierarchy (BVH) is a technique used to efficiently determine which triangle a ray hits first in a complex 3D scene.
• 💾 Modern GPUs with specialized Ray Tracing cores have made real-time rendering with path tracing possible, significantly reducing the time required for complex scenes.

Q & A

What is Ray Tracing and why is it important for TV shows and movies?

Ray Tracing is a computational process that simulates how rays of light bounce off of and illuminate each of the models in a 3D scene, transforming it into a realistic environment. It's important for TV shows and movies because it allows for the creation of highly realistic computer-generated images and special effects.

What is the industry standard algorithm for rendering scenes in TV shows and movies?

The industry standard algorithm for rendering scenes in TV shows and movies is called path tracing. It requires an unimaginable number of calculations to simulate how light interacts with and bounces off every surface in the scene.

How does path tracing work and why does it require so many calculations?

Path tracing simulates how light interacts with and bounces off every surface in a scene by sending out rays from a virtual camera and into the scene. It requires many calculations because it needs to determine which objects the rays hit, how those objects are illuminated by light sources, and account for direct and indirect illumination to produce realistic effects.

What is a bounding volume hierarchy (BVH) and how does it help with ray tracing?

A bounding volume hierarchy (BVH) is a data structure that helps to organize the geometry in a scene by dividing it into a hierarchy of bounding volumes or boxes. This allows for more efficient calculations of ray-triangle intersections by reducing the number of triangles that need to be considered for each ray, thus speeding up the ray tracing process.

How has the advancement of GPUs enabled real-time ray tracing for applications like video games?

The advancement of GPUs, specifically the inclusion of Ray Tracing or RT cores, has enabled real-time ray tracing by allowing for parallel processing of billions of rays per second. This has made it possible to render complex scenes with realistic lighting and reflections in a fraction of the time that was previously required.

What is the difference between primary rays, secondary rays, and shadow rays in ray tracing?

Primary rays are the initial rays emitted from the virtual camera into the scene to determine the first object they hit. Secondary rays are generated after a primary ray hits a surface and bounce off, simulating indirect illumination. Shadow rays are used to determine whether a point on a surface is directly illuminated by a light source or if it's in shadow.

How does indirect illumination contribute to the realism of a rendered scene?

Indirect illumination contributes to the realism of a rendered scene by simulating light bouncing off surfaces and illuminating other objects in the scene. This results in effects like color bleeding from one object to another, and more accurate shading based on the interplay of light and objects in the environment.

What are some of the challenges that were historically associated with implementing path tracing for TV shows and movies?

Historically, the challenges with implementing path tracing included the immense computational requirements, which made it nearly impossible for anything but supercomputers. Additionally, determining which triangle a ray hits first in a scene with millions of triangles was a significant computational problem.

How has the use of ray tracing evolved in video games, and what are some methods employed?

Ray tracing in video games has evolved with methods like using low-resolution duplicates of scenes to create light maps for indirect lighting, and screen space ray tracing which uses the game's generated data like depth and normal maps to create reflections and refractions. These techniques are employed in engines like Unreal Engine's Lumen renderer and games like Cyberpunk.

What role did Steve Jobs play in the development of computer-generated imagery and ray tracing?

Steve Jobs, as the CEO of Pixar from 1986 to 2006, played a significant role in the development of computer-generated imagery and ray tracing. He helped design the computers used to render some of Pixar's first movies, contributing to the advancement of the technology used in CGI.

How does the script describe the process of creating a realistic 3D scene, from modeling to rendering?

The script describes the process of creating a realistic 3D scene as involving several steps: modeling objects and assigning textures, positioning them in a scene with lights and a camera, and then rendering the scene using path tracing to simulate light interactions. This process transforms a simple collection of 3D models into a realistic environment with accurate lighting and reflections.