lighting in real-time and uses more realistic reflections rather than screen space reflections. Nvidia introduced their GeForce RTX and Quadro RTX GPUs September 2018, based on the Turing architecture that allows for hardware-accelerated ray tracing. The Nvidia hardware uses a separate functional block, publicly called an "RT core". This unit is somewhat comparable to a texture unit in size, latency, and interface to the processor core. The unit features BVH traversal, compressed BVH node decompression, ray-AABB intersection testing, and ray-triangle intersection testing. The GeForce RTX, in the form of models 2080 and 2080 Ti, became the first consumer-oriented brand of graphics card that can process ray tracing in real time, and, in November 2018, Electronic Arts' Battlefield V became the first game to take advantage of its ray tracing capabilities, which it achieves via Microsoft's new API, DirectX Raytracing. AMD, which already offered interactive ray tracing on top of OpenCL through its Radeon ProRender, unveiled in October 2020 the Radeon RX 6000 series, its second generation Navi GPUs with support for hardware-accelerated ray tracing at an online event. Subsequent games that render their graphics by such means appeared since, which has been credited to the improvements in hardware and efforts to make more APIs and game engines compatible with the technology. Current home gaming consoles implement dedicated ray tracing hardware components in their GPUs for real-time ray tracing effects, which began with the ninth-generation consoles PlayStation 5, Xbox Series X and Series S. Computational complexity Various complexity results have been proven for certain formulations of the ray tracing problem. In particular, if the decision version of the ray tracing problem is defined as follows – given a light ray's initial position and direction and some fixed point, does the ray eventually reach that point, then the referenced paper proves the following results: Ray tracing in 3D optical systems with a finite set of reflective or refractive objects represented by a system of rational quadratic inequalities is undecidable. Ray tracing in 3D optical systems with a finite set of refractive objects represented by a system of rational linear inequalities is undecidable. Ray tracing in 3D optical systems with a finite set of rectangular reflective or refractive objects is undecidable. Ray tracing in 3D optical systems with a finite set of reflective or partially reflective objects represented by a system of linear inequalities, some of which can be irrational is undecidable. Ray