As graphics processing units evolved, major graphics software libraries such as OpenGL and Direct3D began to support shaders. The first shader-capable GPUs only supported pixel shading, but vertex shaders were quickly introduced once developers realized the power of shaders. The first video card with a programmable pixel shader was the Nvidia GeForce 3 (NV20), released in 2001.[3] Geometry shaders were introduced with Direct3D 10 and OpenGL 3.2. Eventually, graphics hardware evolved toward a unified shader model.
Shaders are simple programs that describe the traits of either a vertex or a pixel. Vertex shaders describe the attributes (position, texture coordinates, colors, etc.) of a vertex, while pixel shaders describe the traits (color, z-depth and alpha value) of a pixel. A vertex shader is called for each vertex in a primitive (possibly after tessellation); thus one vertex in, one (updated) vertex out. Each vertex is then rendered as a series of pixels onto a surface (block of memory) that will eventually be sent to the screen.
There are three types of shaders in common use (pixel, vertex, and geometry shaders), with several more recently added. While older graphics cards utilize separate processing units for each shader type, newer cards feature unified shaders which are capable of executing any type of shader. This allows graphics cards to make more efficient use of processing power.
2D shaders act on digital images, also called textures in the field of computer graphics. They modify attributes of pixels. 2D shaders may take part in rendering 3D geometry. Currently the only type of 2D shader is a pixel shader.
Vertex shaders are the most established and common kind of 3D shader and are run once for each vertex given to the graphics processor. 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).[6] Vertex shaders can manipulate properties such as position, color and texture coordinates, but cannot create new vertices. The output of the vertex shader goes to the next stage in the pipeline, which is either a geometry shader if present, or the rasterizer. Vertex shaders can enable powerful control over the details of position, movement, lighting, and color in any scene involving 3D models.
Geometry shaders were introduced in Direct3D 10 and OpenGL 3.2; formerly available in OpenGL 2.0+ with the use of extensions.[7] This type of shader can generate new graphics primitives, such as points, lines, and triangles, from those primitives that were sent to the beginning of the graphics pipeline.[8]
Geometry shader programs are executed after vertex shaders. They take as input a whole primitive, possibly with adjacency information. For example, when operating on triangles, the three vertices are the geometry shader's input. The shader can then emit zero or more primitives, which are rasterized and their fragments ultimately passed to a pixel shader.
Typical uses of a geometry shader include point sprite generation, geometry tessellation, shadow volume extrusion, and single pass rendering to a cube map. A typical real-world example of the benefits of geometry shaders would be automatic mesh complexity modification. A series of line strips representing control points for a curve are passed to the geometry shader and depending on the complexity required the shader can automatically generate extra lines each of which provides a better approximation of a curve.
As of OpenGL 4.0 and Direct3D 11, a new shader class called a tessellation shader has been added. It adds two new shader stages to the traditional model: tessellation control shaders (also known as hull shaders) and tessellation evaluation shaders (also known as Domain Shaders), which together allow for simpler meshes to be subdivided into finer meshes at run-time according to a mathematical function. 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. This allows objects close to the camera to have fine detail, while further away ones can have more coarse meshes, yet seem comparable in quality. It also can drastically reduce required mesh bandwidth by allowing meshes to be refined once inside the shader units instead of downsampling very complex ones from memory. Some algorithms can upsample any arbitrary mesh, while others allow for "hinting" in meshes to dictate the most characteristic vertices and edges.
Nvidia introduced mesh and task shaders with its Turing microarchitecture in 2018 which are also modelled after compute shaders.[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.[14] These mesh shaders allow the GPU to handle more complex algorithms, offloading more work from the CPU to the GPU, and in algorithm intense rendering, increasing the frame rate of or number of triangles in a scene by an order of magnitude.[15] Intel announced that Intel Arc Alchemist GPUs shipping in Q1 2022 will support mesh shaders.[16]
Compute shaders are not limited to graphics applications, but use the same execution resources for GPGPU. 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.
A programming model with shaders is similar to a higher order function for rendering, taking the shaders as arguments, and providing a specific dataflow between intermediate results, enabling both data parallelism (across pixels, vertices etc.) and pipeline parallelism (between stages). (see also map reduce).
The language in which shaders are programmed depends on the target environment. The official OpenGL and OpenGL ES shading language is OpenGL Shading Language, also known as GLSL, and the official Direct3D shading language is High Level Shader Language, also known as HLSL. Cg, a third-party shading language which outputs both OpenGL and Direct3D shaders, was developed by Nvidia; however since 2012 it has been deprecated. Apple released its own shading language called Metal Shading Language as part of the Metal framework.
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. Automatic compilation then turns the graph into an actual, compiled shader.
I was slightly frustrated with poor performance when playing in VR with the new deferred rendering engine, so I had a look what would be possible to remove/simplify from the shaders to improve the framerate without too huge sacrifices in image quality. Focusing on anything that has a potentially high memory bandwidth cost (which is usually a big problem with deferred renderers + high resolutions) I was able to do some seemingly decent "optimizations".
This seems to happen randomly when the shaders for the cockpit were just compiled. Re-entering the plane/restarting the mission or DCS should fix it and it should not happen any more when the shaders are already compiled.
Shaders written in for example GLSL are typically loaded into a graphics application at runtime. I am wondering why not just compile the application with the shaders so they will not have to be loaded later. Like this:
I don't think this would result in too large of an exe file and it would speed up loading times; unless I'm mistaken about how many shaders are used for a typical graphics application. I realize you may want to update shaders after compile time, but does that really happen?
The OpenGL API specifices GLSL source code being the only way to actually load shaders. There's a caching API (glShaderBinary, glProgramBinary) but the binaries loaded through that are in an unspecified format, that may change at any time, and it's a valid error condition that the driver rejects a binary for whatever reason to enforce loading the original GLSL source. To actually obtain such a shader binary you first load a regular GLSL shader source, compile it and then retrieve a binary blob from OpenGL.
 5527185c55