Shader: Exploring Visual Realms with Shader: A Journey into Computer Vision

Chapter 1: Shader

Shaders are computer programs used in computer graphics that determine how light, dark, and color should be rendered in a 3D environment. Shaders have progressed to serve a wide range of purposes, from general-purpose computing on graphics processing units to specialized tasks in computer graphics and video post-processing.

Conventional shaders are responsible for the flexible computation of rendering effects on graphics hardware. While not strictly necessary, most shaders are written to run on a graphics processing unit (GPU). The traditional fixed-function pipeline for GPU rendering, which only allowed for standard geometry transformations and pixel shading, has been largely replaced by the more flexible and powerful shader programming model. A shader is a computer program that modifies a produced image by changing its position and color (hue, saturation, brightness, and contrast) using techniques defined in the shader and by introducing external variables or textures.

In post-production, CGI, and video games, shaders are used to create a broad variety of visual effects. Shaders are used for a wide variety of effects beyond simple lighting models, including but not limited to: changing an image's hue, saturation, brightness (HSL/HSV), or contrast; creating blur, light bloom, volumetric lighting, normal mapping (for depth effects), bokeh, cel shading, posterization, bump mapping, distortion, chroma keying (for so-called bluescreen/greenscreen effects), edge detection, and motion blur; and psychedelic effects like those seen.

Pixar popularized this sense of the word shader with version 3.0 of the RenderMan Interface Specification, first released in May 1988. With the release of Direct3D 10 and OpenGL 3.2, geometry shaders were available. After some time, graphics hardware converged on a standard shader model.

The characteristics of a vertex or a pixel can be described using shaders, which are small programs. The characteristics of a vertex are described by vertex shaders (such as its position, texture coordinates, colors, etc.), whereas the characteristics of a pixel are described by pixel shaders (such as its color, z-depth, and alpha value). Each vertex in a primitive (potentially after tessellation) triggers a vertex shader call, so the only thing a vertex shader sees is itself. Then, the pixels that make up each vertex are drawn into a surface (a chunk of memory) and passed on to the display.

Shaders take the place of the graphics hardware's Fixed Function Pipeline (FFP), so named because of the predetermined nature with which it handles tasks like lighting and texture mapping. Shaders offer a more flexible, programmatic alternative to this type of inflexible coding.

This is the fundamental graphics pipeline::

Both geometry data and instructions (compiled shading language programs) are sent from the CPU to the GPU on the graphics card.

The vertex shader is where the geometry transformations take place.

When a geometry shader is loaded into the GPU and is active, some alterations to the scene's geometry are made.

Scene geometries can be partitioned if a tessellation shader is present in the GPU and enabled.

Triangulation is used in the computation of geometry (subdivided into triangles).

Triangles are broken down into fragment quads (one fragment quad is a 2 × 2 fragment primitive).

The fragment shader affects the fragment quads in several ways.

Fragments that pass the depth test are drawn to the screen and, potentially, merged with other frames in the frame buffer.

These procedures are used by the graphic pipeline to flatten three-dimensional (or two-dimensional) data into displayable two-dimensional information. Simply put, this is a massive pixel matrix, sometimes known as a frame buffer..

Pixel shaders, vertex shaders, and geometry shaders are the most prevalent, however there are more. In contrast to prior graphics cards, which had dedicated processing units for each shader type, contemporary cards have unified shaders that can run any shader. Because of this, graphics cards can make better use of their resources.

In the field of computer graphics, digital images (also known as textures) are the target of 2D shaders' manipulation. Pixel characteristics are changed by them. It's possible for 2D shaders to help render 3D geometry. Pixel shaders are the sole existing type of 2D shader.

Fragment shaders, or pixel shaders, are responsible for computing the color and other attributes of each fragment of rendering work, which affects no more than a single output pixel. The simplest pixel shaders have a single input and output the color value of a single pixel on the screen, whereas more complicated shaders can process numerous inputs and outputs. There is a wide variety of pixel shaders, some of which simply output a constant color, others which apply a lighting value, and still others which do bump mapping, shadows, specular highlights, translucency, and other effects. In the case of Z-buffering, they can change the fragment's depth, and when rendering to multiple destinations, they can output more than one color. Some complicated effects in 3D graphics cannot be achieved with just a pixel shader since it operates on a single fragment and has no context for the scene's geometry (i.e. vertex data). Pixel shaders, on the other hand, are aware of the screen coordinate being rendered and can take a sample of the screen and neighboring pixels if the complete screen is provided to the shader as a texture. This method can make it possible for cartoon/cel shaders to make use of a wide range of post-processing effects, from blur to edge detection and enhancement. While vertex shaders can only be used with a 3D scene, pixel shaders can be applied at any point in the pipeline to any 2D images (such as sprites or textures). For instance, only a pixel shader can be used as a postprocessor or filter for a rasterized video stream.

3D shaders modify the appearance of meshes and models in 3D space by manipulating their colors and textures. The earliest form of 3D shaders, vertex shaders modify each vertex independently. Recent iterations of geometry shaders include an in-shader vertex generator. Tessellation shaders are the most up-to-date type of 3D shaders; they perform mass operations on groups of vertices at once to increase realism, for example by dynamically subdividing a model into smaller groups of triangles or other primitives to enhance things like curves and bumps, or by altering other attributes.

The most common type of 3D shader, vertex shaders execute once for each vertex passed to the GPU. The goal is to map each vertex's 3D position in virtual space to its corresponding 2D coordinate on the display (as well as a depth value for the Z-buffer). While a vertex shader can modify existing vertices' attributes like color and texture coordinates, it can't generate any new ones. The vertex shader's output is transmitted to the next level of the pipeline, which may be a geometry shader or the rasterizer, depending on the setup. The use of vertex shaders allows for fine-grained manipulation of 3D models' locations, rotations, translations, illumination, and color.

Direct3D 10 and OpenGL 3.2 included geometry shaders, which were previously available in OpenGL 2.0+ via extensions.

After vertex shaders are completed, geometry shader code is run. They want a complete primitive, perhaps with information about its neighbors, as their input. When processing triangles,