Shader

The position and color (hue, saturation, brightness, and contrast) of all pixels, vertices, and/or textures used to construct a final rendered image can be altered using algorithms defined in a shader, and can be modified by external variables or textures introduced by the computer program calling the shader.

[citation needed] Shaders are used widely in cinema post-processing, computer-generated imagery, and video games to produce a range of effects.

[clarification needed] This use of the term "shader" was introduced to the public by Pixar with version 3.0 of their RenderMan Interface Specification, originally published in May 1988.

Shaders replace a section of the graphics hardware typically called the Fixed Function Pipeline (FFP), so-called because it performs lighting and texture mapping in a hard-coded manner.

[5] Pixel shaders range from simply always outputting the same color, to applying a lighting value, to doing bump mapping, shadows, specular highlights, translucency and other phenomena.

In 3D graphics, a pixel shader alone cannot produce some kinds of complex effects because it operates only on a single fragment, without knowledge of a scene's geometry (i.e. vertex data).

The purpose is to transform each vertex's 3D position in virtual space to the 2D coordinate at which it appears on the screen (as well as a depth value for the Z-buffer).

Vertex shaders can enable powerful control over the details of position, movement, lighting, and color in any scene involving 3D models.

The function can be related to a variety of variables, most notably the distance from the viewing camera to allow active level-of-detail scaling.

[11][12] Nvidia Turing is the world's first GPU microarchitecture that supports mesh shading through DirectX 12 Ultimate API, several months before Ampere RTX 30 series was released.

[13] In 2020, AMD and Nvidia released RDNA 2 and Ampere microarchitectures which both support mesh shading through DirectX 12 Ultimate.

They may be used in graphics pipelines e.g. for additional stages in animation or lighting algorithms (e.g. tiled forward rendering).

Some rendering APIs allow compute shaders to easily share data resources with the graphics pipeline.

Ray tracing shaders are supported by Microsoft via DirectX Raytracing, by Khronos Group via Vulkan, GLSL, and SPIR-V,[18] by Apple via Metal.

Tensor shaders are supported by Microsoft via DirectML, by Khronos Group via OpenVX, by Apple via Core ML, by Google via TensorFlow, by Linux Foundation via ONNX.

Shaders are written to apply transformations to a large set of elements at a time, for example, to each pixel in an area of the screen, or for every vertex of a model.

This is well suited to parallel processing, and most modern GPUs have multiple shader pipelines to facilitate this, vastly improving computation throughput.

Modern video game development platforms such as Unity, Unreal Engine and Godot increasingly include node-based editors that can create shaders without the need for actual code; the user is instead presented with a directed graph of connected nodes that allow users to direct various textures, maps, and mathematical functions into output values like the diffuse color, the specular color and intensity, roughness/metalness, height, normal, and so on.

An example of two kinds of shadings: Flat shading on the left and Phong shading on the right. Phong shading is an improvement on Gouraud shading , and was one of the first computer shading models developed after the basic flat shader, greatly enhancing the appearance of curved surfaces in renders. Shaders are most commonly used to produce lit and shadowed areas in the rendering of 3D models .
Another use of shaders is for special effects, even on 2D images, (e.g., a photo from a webcam ). The unaltered, unshaded image is on the left, and the same image has a shader applied on the right. This shader works by replacing all light areas of the image with white, and all dark areas with a brightly colored texture.