GPU Raycasting

A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobile phones, personal computers, workstations, and game consoles.

Modern GPUs are efficient at manipulating computer graphics and image processing. Their parallel structure makes them more efficient than general-purpose central processing units (CPUs) for algorithms that process large blocks of data in parallel. In a personal computer, a GPU can be present on a video card or embedded on the motherboard. In some CPUs, they are embedded on the CPU die.

In the 1970s, the term "GPU" originally stood for ''graphics processor unit'' and described a programmable processing unit independently working from the CPU and responsible for graphics manipulation and output. Later, in 1994, Sony used the term (now standing for ''graphics processing unit'') in reference to the PlayStation console's Toshiba-designed Sony GPU in 1994. The term was popularized by Nvidia in 1999, who marketed the GeForce 256 as "the world's first GPU". It was presented as a "single-chip processor with integrated transform, lighting, triangle setup/clipping, and rendering engines". Rival ATI Technologies coined the term "visual processing unit" or VPU with the release of the Radeon 9700 in 2002.

History

1970s

Arcade system boards have been using specialized graphics circuits since the 1970s. In early video game hardware, the RAM for frame buffers was expensive, so video chips composited data together as the display was being scanned out on the monitor.

A specialized barrel shifter circuit was used to help the CPU animate the framebuffer graphics for various 1970s arcade games from Midway and Taito, such as '' Gun Fight'' (1975), '' Sea Wolf'' (1976) and '' Space Invaders'' (1978). The Namco Galaxian arcade system in 1979 used specialized graphics hardware supporting RGB color, multi-colored sprites and tilemap backgrounds. The Galaxian hardware was widely used during the golden age of arcade video games, by game companies such as Namco, Centuri, Gremlin, Irem, Konami, Midway, Nichibutsu, Sega and Taito.

In the home market, the Atari 2600 in 1977 used a video shifter called the Television Interface Adaptor. The Atari 8-bit computers (1979) had ANTIC, a video processor which interpreted instructions describing a "display list"—the way the scan lines map to specific bitmapped or character modes and where the memory is stored (so there did not need to be a contiguous frame buffer). 6502 machine code subroutines could be triggered on scan lines by setting a bit on a display list instruction. ANTIC also supported smooth vertical and horizontal scrolling independent of the CPU.

1980s

The NEC µPD7220 was the first implementation of a PC graphics display processor as a single Large Scale Integration (LSI) integrated circuit chip, enabling the design of low-cost, high-performance video graphics cards such as those from Number Nine Visual Technology. It became the best-known GPU up until the mid-1980s. It was the first fully integrated VLSI (very large-scale integration) metal-oxide-semiconductor ( NMOS) graphics display processor for PCs, supported up to 1024x1024 resolution, and laid the foundations for the emerging PC graphics market. It was used in a number of graphics cards and was licensed for clones such as the Intel 82720, the first of Intel's graphics processing units. The Williams Electronics arcade games ''Robotron 2084'', '' Joust'', '' Sinistar'', and ''Bubbles'', all released in 1982, contain custom blitter chips for operating on 16-color bitmaps.

In 1984, Hitachi released ARTC HD63484, the first major CMOS graphics processor for PC. The ARTC was capable of displaying up to 4K resolution when in monochrome mode, and it was used in a number of PC graphics cards and terminals during the late 1980s. In 1985, the Commodore Amiga featured a custom graphics chip, with a blitter unit accelerating bitmap manipulation, line draw, and area fill functions. Also included is a coprocessor with its own simple instruction set, capable of manipulating graphics hardware registers in sync with the video beam (e.g. for per-scanline palette switches, sprite multiplexing, and hardware windowing), or driving the blitter. In 1986, Texas Instruments released the TMS34010, the first fully programmable graphics processor. It could run general-purpose code, but it had a graphics-oriented instruction set. During 1990–1992, this chip became the basis of the Texas Instruments Graphics Architecture ("TIGA") Windows accelerator cards.

In 1987, the IBM 8514 graphics system was released as one of the first video cards for IBM PC compatibles to implement fixed-function 2D primitives in electronic hardware. Sharp's X68000, released in 1987, used a custom graphics chipset with a 65,536 color palette and hardware support for sprites, scrolling, and multiple playfields, eventually serving as a development machine for Capcom's CP System arcade board. Fujitsu later competed with the FM Towns computer, released in 1989 with support for a full 16,777,216 color palette. In 1988, the first dedicated polygonal 3D graphics boards were introduced in arcades with the Namco System 21 and Taito Air System.

IBM's proprietary