Computer graphics are pictures and films created using computers. The term refers to computer-generated image data created with the help of specialized graphical hardware and software, it is a vast and developed area of computer science. The phrase was coined in 1960, by computer graphics researchers Verne Hudson and William Fetter of Boeing, it is abbreviated as CG, though sometimes erroneously referred to as computer-generated imagery. Some topics in computer graphics include user interface design, sprite graphics, vector graphics, 3D modeling, shaders, GPU design, implicit surface visualization with ray tracing, computer vision, among others; the overall methodology depends on the underlying sciences of geometry and physics. Computer graphics is responsible for displaying art and image data and meaningfully to the consumer, it is used for processing image data received from the physical world. Computer graphics development has had a significant impact on many types of media and has revolutionized animation, advertising, video games, graphic design in general.
The term computer graphics has been used in a broad sense to describe "almost everything on computers, not text or sound". The term computer graphics refers to several different things: the representation and manipulation of image data by a computer the various technologies used to create and manipulate images the sub-field of computer science which studies methods for digitally synthesizing and manipulating visual content, see study of computer graphicsToday, computer graphics is widespread; such imagery is found in and on television, weather reports, in a variety of medical investigations and surgical procedures. A well-constructed graph can present complex statistics in a form, easier to understand and interpret. In the media "such graphs are used to illustrate papers, theses", other presentation material. Many tools have been developed to visualize data. Computer generated imagery can be categorized into several different types: two dimensional, three dimensional, animated graphics; as technology has improved, 3D computer graphics have become more common, but 2D computer graphics are still used.
Computer graphics has emerged as a sub-field of computer science which studies methods for digitally synthesizing and manipulating visual content. Over the past decade, other specialized fields have been developed like information visualization, scientific visualization more concerned with "the visualization of three dimensional phenomena, where the emphasis is on realistic renderings of volumes, illumination sources, so forth with a dynamic component"; the precursor sciences to the development of modern computer graphics were the advances in electrical engineering and television that took place during the first half of the twentieth century. Screens could display art since the Lumiere brothers' use of mattes to create special effects for the earliest films dating from 1895, but such displays were limited and not interactive; the first cathode ray tube, the Braun tube, was invented in 1897 – it in turn would permit the oscilloscope and the military control panel – the more direct precursors of the field, as they provided the first two-dimensional electronic displays that responded to programmatic or user input.
Computer graphics remained unknown as a discipline until the 1950s and the post-World War II period – during which time the discipline emerged from a combination of both pure university and laboratory academic research into more advanced computers and the United States military's further development of technologies like radar, advanced aviation, rocketry developed during the war. New kinds of displays were needed to process the wealth of information resulting from such projects, leading to the development of computer graphics as a discipline. Early projects like the Whirlwind and SAGE Projects introduced the CRT as a viable display and interaction interface and introduced the light pen as an input device. Douglas T. Ross of the Whirlwind SAGE system performed a personal experiment in which a small program he wrote captured the movement of his finger and displayed its vector on a display scope. One of the first interactive video games to feature recognizable, interactive graphics – Tennis for Two – was created for an oscilloscope by William Higinbotham to entertain visitors in 1958 at Brookhaven National Laboratory and simulated a tennis match.
In 1959, Douglas T. Ross innovated again while working at MIT on transforming mathematic statements into computer generated 3D machine tool vectors by taking the opportunity to create a display scope image of a Disney cartoon character. Electronics pioneer Hewlett-Packard went public in 1957 after incorporating the decade prior, established strong ties with Stanford University through its founders, who were alumni; this began the decades-long transformation of the southern San Francisco Bay Area into the world's leading computer technology hub - now known as Silicon Valley. The field of computer graphics developed with the emergence of computer graphics hardware. Further advances in computing led to greater advancements in interactive computer graphics. In 1959, the TX-2 computer was developed at MIT's Lincoln Laboratory; the TX-2 integrated a number of new man-machine interfaces. A light pen could be used to draw sketches on the computer using Ivan Sutherland's revolutionary Sketchpad software.
Using a light pen, Sketchpad allowed one to draw simple shapes on the computer screen, save them and recall them later. The light pen itself had a small photoelectric cell in its tip. T
Ray tracing (graphics)
In computer graphics, ray tracing is a rendering technique for generating an image by tracing the path of light as pixels in an image plane and simulating the effects of its encounters with virtual objects. The technique is capable of producing a high degree of visual realism higher than that of typical scanline rendering methods, but at a greater computational cost; this makes ray tracing best suited for applications where taking a long time to render a frame can be tolerated, such as in still images and film and television visual effects, more poorly suited for real-time applications such as video games where speed is critical. Ray tracing is capable of simulating a wide variety of optical effects, such as reflection and refraction and dispersion phenomena. Optical ray tracing describes a method for producing visual images constructed in 3D computer graphics environments, with more photorealism than either ray casting or scanline rendering techniques, it works by tracing a path from an imaginary eye through each pixel in a virtual screen, calculating the color of the object visible through it.
Scenes in ray tracing are described mathematically by a visual artist. Scenes may incorporate data from images and models captured by means such as digital photography; each ray must be tested for intersection with some subset of all the objects in the scene. Once the nearest object has been identified, the algorithm will estimate the incoming light at the point of intersection, examine the material properties of the object, combine this information to calculate the final color of the pixel. Certain illumination algorithms and reflective or translucent materials may require more rays to be re-cast into the scene, it may at first seem counterintuitive or "backward" to send rays away from the camera, rather than into it, but doing so is many orders of magnitude more efficient. Since the overwhelming majority of light rays from a given light source do not make it directly into the viewer's eye, a "forward" simulation could waste a tremendous amount of computation on light paths that are never recorded.
Therefore, the shortcut taken in raytracing is to presuppose that a given ray intersects the view frame. After either a maximum number of reflections or a ray traveling a certain distance without intersection, the ray ceases to travel and the pixel's value is updated. On input we have: E ∈ R 3 eye position T ∈ R 3 target position θ ∈ [ 0, π ) field of view - for human we can assume ≈ π / 2 rad = 90 ∘ m, k ∈ N numbers of square pixels on viewport vertical and horizontal direction i, j ∈ N, 1 ≤ i ≤ k ∧ 1 ≤ j ≤ m numbers of actual pixel w → ∈ R 3 vertical vector which indicates where is up and down w → = - roll component which determine viewport rotation around point C The idea is to find the position of each viewport pixel center P i j which allows us to find the line going from eye E through that pixel and get the ray described by point E and vector R → i j = P i j − E. First we need to find the coordinates of the bottom left viewport pixel P 1 m and find the next pixel by making a shift along directions parallel to viewport multiplied by the size of the pixel.
Below we introduce formulas which include distance d between the eye and the viewport. However, this value will be reduced during ray normalization r → i j. Pre-calculations: let's find and normalise vector t → and vectors b →, v → which are parallel to the viewport t → = T
Texture mapping is a method for defining high frequency detail, surface texture, or color information on a computer-generated graphic or 3D model. Its application to 3D graphics was pioneered by Edwin Catmull in 1974. Texture mapping referred to a method that wrapped and mapped pixels from a texture to a 3D surface. In recent decades, the advent of multi-pass rendering and complex mapping such as height mapping, bump mapping, normal mapping, displacement mapping, reflection mapping, specular mapping, occlusion mapping, many other variations on the technique have made it possible to simulate near-photorealism in real time by vastly reducing the number of polygons and lighting calculations needed to construct a realistic and functional 3D scene. A texture map is an image applied to the surface of a polygon; this may be a procedural texture. They may be stored in common image file formats, referenced by 3d model formats or material definitions, assembled into resource bundles, they may have 1-3 dimensions.
For use with modern hardware, texture map data may be stored in swizzled or tiled orderings to improve cache coherency. Rendering APIs manage texture map resources as buffers or surfaces, may allow'render to texture' for additional effects such as post processing, environment mapping, they contain RGB color data, sometimes an additional channel for alpha blending for billboards and decal overlay textures. It is possible to use the alpha channel for other uses such as specularity. Multiple texture maps may be combined for control over specularity, displacement, or subsurface scattering e.g. for skin rendering. Multiple texture images may be combined in texture atlases or array textures to reduce state changes for modern hardware.. Modern hardware supports cube map textures with multiple faces for environment mapping. Texture maps may be acquired by scanning/digital photography, authored in image manipulation software such as GIMP, Photoshop, or painted onto 3D surfaces directly in a 3D paint tool such as Mudbox or zbrush.
This process is akin to applying patterned paper to a plain white box. Every vertex in a polygon is assigned a texture coordinate; this may be done through explicit assignment of vertex attributes, manually edited in a 3D modelling package through UV unwrapping tools. It is possible to associate a procedural transformation from 3d space to texture space with the material; this might be accomplished via planar projection or, cylindrical or spherical mapping. More complex mappings may consider the distance along a surface to minimize distortion; these coordinates are interpolated across the faces of polygons to sample the texture map during rendering. Textures may be repeated or mirrored to extend a finite rectangular bitmap over a larger area, or they may have a one-to-one unique "injective" mapping from every piece of a surface. Texture mapping maps the model surface into texture space. UV unwrapping tools provide a view in texture space for manual editing of texture coordinates; some rendering techniques such as subsurface scattering may be performed by texture-space operations.
Multitexturing is the use of more than one texture at a time on a polygon. For instance, a light map texture may be used to light a surface as an alternative to recalculating that lighting every time the surface is rendered. Microtextures or detail textures are used to add higher frequency details, dirt maps may add weathering and variation. Modern graphics may use more than 10 layers, for greater fidelity. Another multitexture technique is bump mapping, which allows a texture to directly control the facing direction of a surface for the purposes of its lighting calculations. Bump mapping has become popular in recent video games, as graphics hardware has become powerful enough to accommodate it in real-time; the way that samples are calculated from the texels is governed by texture filtering. The cheapest method is to use the nearest-neighbour interpolation, but bilinear interpolation or trilinear interpolation between mipmaps are two used alternatives which reduce aliasing or jaggies. In the event of a texture coordinate being outside the texture, it is either wrapped.
Anisotropic filtering better eliminates directional artefacts when viewing textures from oblique viewing angles. As an optimization, it is possible to render detail from a high resolution model or expensive process into a surface texture; this is known as render mapping. This technique is most used for lightmapping but may be used to generate normal maps and displacement maps; some video games have used this technique. The original Quake software engine used on-the-fly baking to combi
In computer graphics, environment mapping, or reflection mapping, is an efficient image-based lighting technique for approximating the appearance of a reflective surface by means of a precomputed texture image. The texture is used to store the image of the distant environment surrounding the rendered object. Several ways of storing the surrounding environment are employed; the first technique was sphere mapping, in which a single texture contains the image of the surroundings as reflected on a mirror ball. It has been entirely surpassed by cube mapping, in which the environment is projected onto the six faces of a cube and stored as six square textures or unfolded into six square regions of a single texture. Other projections that have some superior mathematical or computational properties include the paraboloid mapping, the pyramid mapping, the octahedron mapping, the HEALPix mapping; the reflection mapping approach is more efficient than the classical ray tracing approach of computing the exact reflection by tracing a ray and following its optical path.
The reflection color used in the shading computation at a pixel is determined by calculating the reflection vector at the point on the object and mapping it to the texel in the environment map. This technique produces results that are superficially similar to those generated by raytracing, but is less computationally expensive since the radiance value of the reflection comes from calculating the angles of incidence and reflection, followed by a texture lookup, rather than followed by tracing a ray against the scene geometry and computing the radiance of the ray, simplifying the GPU workload. However, in most circumstances a mapped reflection is only an approximation of the real reflection. Environment mapping relies on two assumptions that are satisfied: 1) All radiance incident upon the object being shaded comes from an infinite distance; when this is not the case the reflection of nearby geometry appears in the wrong place on the reflected object. When this is the case, no parallax is seen in the reflection.
2) The object being shaded is convex, such that it contains no self-interreflections. When this is not the case the object does not appear in the reflection. Reflection mapping is a traditional image-based lighting technique for creating reflections of real-world backgrounds on synthetic objects. Environment mapping is the fastest method of rendering a reflective surface. To further increase the speed of rendering, the renderer may calculate the position of the reflected ray at each vertex; the position is interpolated across polygons to which the vertex is attached. This eliminates the need for recalculating every pixel's reflection direction. If normal mapping is used, each polygon has many face normals, which can be used in tandem with an environment map to produce a more realistic reflection. In this case, the angle of reflection at a given point on a polygon will take the normal map into consideration; this technique is used to make an otherwise flat surface appear textured, for example corrugated metal, or brushed aluminium.
Sphere mapping represents the sphere of incident illumination as though it were seen in the reflection of a reflective sphere through an orthographic camera. The texture image can be created by approximating this ideal setup, or using a fisheye lens or via prerendering a scene with a spherical mapping; the spherical mapping suffers from limitations that detract from the realism of resulting renderings. Because spherical maps are stored as azimuthal projections of the environments they represent, an abrupt point of singularity is visible in the reflection on the object where texel colors at or near the edge of the map are distorted due to inadequate resolution to represent the points accurately; the spherical mapping wastes pixels that are in the square but not in the sphere. The artifacts of the spherical mapping are so severe that it is effective only for viewpoints near that of the virtual orthographic camera. Cube mapping and other polyhedron mappings address the severe distortion of sphere maps.
If cube maps are made and filtered they have no visible seams, can be used independent of the viewpoint of the often-virtual camera acquiring the map. Cube and other polyhedron maps have since superseded sphere maps in most computer graphics applications, with the exception of acquiring image-based lighting. Image-based Lighting can be done with parallax-corrected cube maps. Cube mapping uses the same skybox, used in outdoor renderings. Cube-mapped reflection is done by determining the vector; this camera ray is reflected about the surface normal of where the camera vector intersects the object. This results in the reflected ray, passed to the cube map to get the texel which provides the radiance value used in the lighting calculation; this creates the effect. HEALPix environment mapping is similar to the other polyhedron mappings, but can be hierarchical, thus providing a unified framework for generating polyhedra that better approximate the sphere; this allows lower distortion at the cost of increased computation.
Precursor work in texture mapping had been established by Edwin Catmull, with refinements for curved surfaces by James Blinn, in 1974. Blinn went on to further refine his work, developing environment mapping by 1976. Gene Miller experimented with spherical environment mapping in 1982 at MAGI Synthavision. Wolfgang Heidrich introduced Paraboloid Mapping in 1998. Emil Praun introduced Octahedron Mapping in 2003. Mauro Steigleder introduced Pyramid Mapping in 2005. Tien-Tsin Wong, et al. introduced the existing HEALPix mapping for rende
Displacement mapping is an alternative computer graphics technique in contrast to bump mapping, normal mapping, parallax mapping, using a texture- or height map to cause an effect where the actual geometric position of points over the textured surface are displaced along the local surface normal, according to the value the texture function evaluates to at each point on the surface. It gives surfaces a great sense of depth and detail, permitting in particular self-occlusion, self-shadowing and silhouettes. For years, displacement mapping was a peculiarity of high-end rendering systems like PhotoRealistic RenderMan, while realtime APIs, like OpenGL and DirectX, were only starting to use this feature. One of the reasons for this is that the original implementation of displacement mapping required an adaptive tessellation of the surface in order to obtain enough micropolygons whose size matched the size of a pixel on the screen. Displacement mapping includes the term mapping which refers to a texture map being used to modulate the displacement strength.
The displacement direction is the local surface normal. Today, many renderers allow programmable shading which can create high quality procedural textures and patterns at arbitrarily high frequencies; the use of the term mapping becomes arguable as no texture map is involved anymore. Therefore, the broader term displacement is used today to refer to a super concept that includes displacement based on a texture map. Renderers using the REYES algorithm, or similar approaches based on micropolygons, have allowed displacement mapping at arbitrary high frequencies since they became available 20 years ago; the first commercially available renderer to implement a micropolygon displacement mapping approach through REYES was Pixar's PhotoRealistic RenderMan. Micropolygon renderers tessellate geometry themselves at a granularity suitable for the image being rendered; that is: the modeling application delivers high-level primitives to the renderer. Examples include true NURBS- or subdivision surfaces; the renderer tessellates this geometry into micropolygons at render time using view-based constraints derived from the image being rendered.
Other renderers that require the modeling application to deliver objects pre-tessellated into arbitrary polygons or triangles have defined the term displacement mapping as moving the vertices of these polygons. The displacement direction is limited to the surface normal at the vertex. While conceptually similar, those polygons are a lot larger than micropolygons; the quality achieved from this approach is thus limited by the geometry's tessellation density a long time before the renderer gets access to it. This difference between displacement mapping in micropolygon renderers vs. displacement mapping in a non-tessellating polygon renderers can lead to confusion in conversations between people whose exposure to each technology or implementation is limited. More so, as in recent years, many non-micropolygon renderers have added the ability to do displacement mapping of a quality similar to that which a micropolygon renderer is able to deliver naturally. To distinguish between the crude pre-tessellation-based displacement these renderers did before, the term sub-pixel displacement was introduced to describe this feature.
Sub-pixel displacement refers to finer re-tessellation of geometry, tessellated into polygons. This re-tessellation results in micropolygons or microtriangles; the vertices of these get moved along their normals to achieve the displacement mapping. True micropolygon renderers have always been able to do what sub-pixel-displacement achieved only but at a higher quality and in arbitrary displacement directions. Recent developments seem to indicate that some of the renderers that use sub-pixel displacement move towards supporting higher level geometry too; as the vendors of these renderers are to keep using the term sub-pixel displacement, this will lead to more obfuscation of what displacement mapping stands for, in 3D computer graphics. In reference to Microsoft's proprietary High Level Shader Language, displacement mapping can be interpreted as a kind of "vertex-texture mapping" where the values of the texture map do not alter pixel colors, but instead change the position of vertices. Unlike bump and parallax mapping, all of which can be said to "fake" the behavior of displacement mapping, in this way a genuinely rough surface can be produced from a texture.
It has to be used in conjunction with adaptive tessellation techniques to produce detailed meshes. Heightmap Sculpted prim Blender Displacement Mapping Relief Texture Mapping website Parallax Occlusion Mapping in GLSL on sunandblackcat.com Real-Time Relief Mapping on Arbitrary Polygonal Surfaces paper Relief Mapping of Non-Height-Field Surface Details paper Steep Parallax Mapping website State of the art of displacement mapping on the gpu paper