What is ray tracing? The graphics technique explained!

Ray tracing is a type of graphics tech­no­logy that real­ist­ic­ally cal­cu­lates visible and invisible rays of light. It enables lifelike lighting in computer games and animated 3D graphics and is in­creas­ingly used as a hardware feature in the form of real-time ray tracing. So, what exactly is ray tracing?

In principle, the function of ray tracing is simple. First, a 3D graphic with 3D objects is designed with 3D modelling software (e.g., Blender or Cinema 4D) and is then animated as a scene. To simulate lifelike lighting in realistic 3D land­scapes, light sources are placed to make 3D objects ‘visible’. This is where ray tracing comes into play. Like in all 3D an­im­a­tions, a virtual camera acts as the eye of the viewer. With the help of ray tracing tech­no­logy, the algorithm draws rays and lines between objects and the camera and works out whether these are visible for the camera and how many pixels each line needs.

In addition, ray tracing iden­ti­fies whether rays of light come from original light sources or from reflected objects in the field of view of the camera. The algorithm then defines pixel colours based on the tracked rays, re­flec­tions, incidence of light and surface textures. Even objects and light sources that cannot be seen are included in the rendering. The result is a realistic lighting model with complex light and shadow effects in real time. In addition, Nvidia’s RTX tech­no­logy works with a type of ar­ti­fi­cial in­tel­li­gence known as ‘Deep Learning Super Sampling’ in order to get an optimal res­ol­u­tion and frame rate.

The extent to which ray tracing affects the realism of a 3D graphic depends on the type of ray tracing used. Below we have listed different ray tracing methods in ascending order according to the computing power required and his­tor­ic­al de­vel­op­ment:

1. Hidden-surface de­term­in­a­tion: This rudi­ment­ary de­term­in­a­tion process does not include shadow or light effects in the animation.
2. Shadow sim­u­la­tion: Direct light sources and hard shadows are used but re­flec­tion effects are not cal­cu­lated.
3. Recursive ray tracing: In addition to direct light sources and hard shadows, ray tracing for mirror re­flec­tion is used with trans­lu­cent or re­flect­ive objects.
4. Diffuse ray tracing: In addition to direct lighting and re­frac­tion, umbra/penumbra and soft shadow edges are rendered.
5. Path ray tracing: The lighting model includes and records visible and invisible light sources, re­flec­tions, and re­frac­tions through lit objects. This creates realistic shadow sim­u­la­tions according to the play of light.

Ray tracing is primarily used in 3D computer graphics and has become more well-known by computer gamers since Nvidia’s RTX graphics card gen­er­a­tion was in­tro­duced in 2018. With ray tracing that is activated or supported by hardware, it is now possible to create even more effective and realistic light effects in video games. The graphic effects not only include light effects visible in the field of vision (so-called screen­space effects), but also re­flec­tions, light, and shadow outside the field of vision – including a global, virtual sun. Since this requires enormous computing power, even for hardware with ray tracing, this feature has only been used in a few games so far.

Ray tracing as a graphics tech­no­logy is still only in its infancy. Currently, the Nvidia’s RTX 3000 series (the 2^nd gen­er­a­tion of Nvidia RTX graphics cards) represent the next step in ray tracing as they offer even more ray tracing arith­met­ic units. Due to the different equipment of PCs and the enormous per­form­ance re­quire­ments, the tech­no­logy, which is re­volu­tion­ary in its approach, remains a niche graphics tech­no­logy for the time being. The newer console gen­er­a­tions, such as the Xbox Series X or Play­Sta­tion 5, are making the first steps towards sup­port­ing global ray tracing through the im­ple­ment­a­tion of hardware which supports the tech­no­logy.

Until now, only a few hardware and software systems supported ray tracing tech­no­logy. To display games and an­im­a­tions with fluid ray tracing, a fast, powerful computer and RTX graphic card are essential. Often costly PC upgrades are needed in order to possess the necessary computing power. Graphic cards that offer ray tracing support include the first and second Nvidia RTX gen­er­a­tion graphic cards (e.g., the GeForce RTX 2070 and GeForce RTX 3070). Certain AMD graphics cards from the Radeon-RX-6000 gen­er­a­tion, such as the RX 6800 and RX 6900 XT, also already support ray tracing.

A range of different PC and computer games already offer ray tracing support.

• Minecraft RTX
• Shadow of the Tomb Raider
• The Witcher 3: Complete Edition
• Call of Duty: Black Ops Cold War
• Control
• F1 2021

• Gran Turismo 7
• Halo Infinite
• Watch Dogs: Legion
• Gears 5