What is Ray Tracing

Ray tracing is a rendering technique used to add realistic light effects in 3D scenes. It is a relatively advanced concept in computer graphics, and it has been used to create stunning visuals for decades. Ray tracing involves tracing the path of light as pixels in an image to simulate its effects such as the formation of shadows, reflections, etc.

History

The idea was first announced in the 16th century by Albrecht Dürer. One of the described techniques was what geometry is visible along a given ray, as is done with ray tracing.

Aurther Appel was the first to use a computer for ray tracing to generate shaded geometric pictures in 1968.

In 1971 Goldstein and Nagel published “3D visual simulation” in which ray tracing is used to make shaded pictures out of solids by simulating the photographic process in reverse.

The concept was also put to use in the early 1970s when it was used for the rendering of three-dimensional images in the movie “Futureworld.” 

Scott Roth created a flip book animation in Bob Sproull’s computer graphics course at Caltech in 1976. In Roth’s computer program, if a ray intersects a plane different from its neighbors, an edge point was noted. It’s true that rays can intersect more than one plane in space, but only the closest surface point is visible. The edges are jagged because the time-sharing DEC PDP-10 only had a coarse resolution. For the display of text and graphics there was a tektronix storage-tube called “terminal”. An image of the display was printed on rolling thermal paper by a printer attached to the display. Roth extended the framework and coined the term “ray casting” in the context of computer graphics and solid modeling.

In the 1980s, ray tracing was further refined, leading to the development of the RenderMan software used in Hollywood films such as “Tron” and “Toy Story.” The increased realism of ray tracing allowed filmmakers to create more realistic and believable visuals for their films.

How it works

Ray tracing works by tracing the path of light rays from the camera through the virtual scene. As the rays encounter objects in the image, the color, texture, and other properties of the object are used to determine the color of the pixel and its effects in reality. The process is repeated as each pixel is processed and the scene is rendered.  

Where is it used

Ray tracing is used in movies, video games, and virtual reality applications. Movies such as Avatar and Gravity use ray tracing to create realistic visuals. Video games like Call of Duty and Battlefield use ray tracing to create realistic lighting and shadows. And virtual reality applications like Google Earth use ray tracing to create a realistic virtual world.  

How to use it

To use ray tracing, a 3D scene must be created in a 3D modeling program, such as Blender or Maya, and then rendered with a ray tracer, such as V-Ray or Arnold. The ray tracer then takes the 3D model and traces the path of light rays in the scene. Once the scene is rendered, the resulting image can be adjusted and tuned to get the look wanted by us.

The Ray Tracing Algorithm

Turner Whitted was the first to show recursive ray tracing for mirror reflection and for refraction through translucent objects, with an angle determined by the solid’s index of refraction, and to use ray tracing for anti-aliasing. Whitted also showed ray traced shadows. He produced a recursive ray-traced film called “The Compleat Angler” in 1979.  

The ray tracing algorithm is based on the concept of tracing the path of light from a specific source through a three-dimensional scene. It begins by tracing a single ray from the camera to a point in the scene, and then tracing the ray of light reflected from that point. The resulting ray is then traced to another point in the scene, and the process is repeated until the ray reaches the camera. This process is repeated for each pixel in the image, resulting in an accurate and realistic rendering of the scene.

How/Where is Ray Tracing used in Graphics Card 

Ray tracing is used in graphics cards to determine which pixels should be illuminated, and which should be left in the dark as it’s a crucial part of creating realistic lighting effects. Ray tracing can also be used to create more realistic reflections and refractions, which can be used to create more believable water and glass surfaces.

For graphics card manufacturers, ray tracing provides an efficient way of creating realistic images without having to resort to more traditional methods. By using ray tracing, graphics card manufacturers can reduce the amount of time it takes to render an image, as well as reducing the amount of power it requires. This helps to make graphics cards more energy-efficient, and can result in improved performance in games and other applications.

Advantages of Ray Tracing

First- ray tracing produces more realistic images due to its ability to simulate a wide range of natural phenomena such as reflection, refraction, shadows, and global illumination. This allows for a more realistic representation of light and shadow in 3D scenes, which is not possible with traditional rendering techniques.

Second- ray tracing can also be used to generate high-quality images in real-time. This makes it well-suited to applications such as virtual reality and augmented reality, where the user needs to interact with the environment in real-time.

Third- ray tracing is much more efficient than traditional rendering techniques. Traditional rendering techniques require significant amounts of computing power to render an image, whereas ray tracing requires significantly less computing power to produce the same result.

Lastly- ray tracing is incredibly versatile. It can be used for a wide range of 3D applications, from architectural renderings to medical imaging. It is also used in motion picture production and video game development.

Disadvantages of Ray Tracing 

The first issue is its high computational cost. Ray tracing requires a great deal of processing power to calculate the paths of light rays which are used to generate the realistic images. This makes it unsuitable for real-time applications, such as video games, where the rendering must be done quickly in order to produce a smooth experience. 

Another disadvantage of ray tracing is its dependence on large amounts of memory. The memory required to store the scene data and the data related to the light rays for rendering can be quite significant, making it difficult to render complex scenes. 

Finally, ray tracing is difficult to parallelize, making it less efficient in multi-core environments. Parallelization involves splitting up the workload to be processed across multiple cores, resulting in faster rendering times. However, due to the nature of ray tracing, this is not easily achievable. 

Global Illumination 

Global Illumination is a lighting technique used in 3D rendering that simulates more realistic lighting. This technique accounts for indirect illumination, or light bouncing off other surfaces in the scene. This allows for more realistic shadows, reflections, and diffuse lighting. Global Illumination also accounts for the color of light as it bounces off surfaces, creating more realistic lighting effects.

In order to accurately simulate Global Illumination, the rendering engine needs to solve the rendering equation. This equation uses direct lighting, indirect lighting, specular reflections, and diffuse reflections. By solving this equation, the engine can accurately simulate how light interacts with the 3D scene and create more realistic lighting effects. 

Global Illumination can be further enhanced by using techniques such as ray tracing and path tracing. These techniques allow the lighting engine to simulate more complex light interactions, such as caustics, reflection and refraction, and indirect occlusion.

– Saanvi Verma