![Texture mapping demonstration animation](https://upload.wikimedia.org/wikipedia/commons/f/f2/Texture_mapping_demonstration_animation.gif)
Texture mapping is a method for mapping a texture on a
computer-generated graphic. Texture here can be high frequency
detail Detail(s) or The Detail(s) may refer to:
Film and television
* ''Details'' (film), a 2003 Swedish film
* ''The Details'' (film), a 2011 American film
* ''The Detail'', a Canadian television series
* "The Detail" (''The Wire''), a television epis ...
,
surface texture
Surface finish, also known as surface texture or surface topography, is the nature of a surface as defined by the three characteristics of lay, surface roughness, and waviness.. It comprises the small, local deviations of a surface from the perf ...
, or
color
Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...
.
History
The original technique was pioneered by
Edwin Catmull
Edwin Earl "Ed" Catmull (born March 31, 1945) is an American computer scientist who is the co-founder of Pixar and was the President of Walt Disney Animation Studios. He has been honored for his contributions to 3D computer graphics (computer sci ...
in 1974.
Texture mapping originally referred to diffuse mapping, a method that simply mapped
pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the smal ...
s from a texture to a
3D surface ("wrapping" the image around the object). In recent decades, the advent of multi-pass rendering,
multitexturing
Texture mapping is a method for mapping a texture on a computer-generated graphic. Texture here can be high frequency detail, surface texture, or color.
History
The original technique was pioneered by Edwin Catmull in 1974.
Texture mapping ...
,
mipmaps
In computer graphics, mipmaps (also MIP maps) or pyramids are pre-calculated, optimization (computer science), optimized sequences of digital image, images, each of which is a progressively lower image resolution, resolution representation of the ...
, and more complex mappings such as
height mapping
In computer graphics, a heightmap or heightfield is a raster graphics, raster image used mainly as Discrete Global Grid in digital elevation model#Types_of_DEM, secondary elevation modeling. Each pixel stores values, such as surface elevatio ...
,
bump mapping
Bump mapping is a texture mapping technique in computer graphics for simulating bumps and wrinkles on the surface of an object. This is achieved by perturbing the surface normals of the object and using the perturbed normal during lighting cal ...
,
normal mapping
In 3D computer graphics, normal mapping, or Dot3 bump mapping, is a texture mapping technique used for faking the lighting of bumps and dents – an implementation of bump mapping. It is used to add details without using more polygons. A common u ...
,
displacement mapping
Displacement mapping is an alternative computer graphics technique in contrast to bump, normal, and parallax mapping, using a texture or height map to cause an effect where the actual geometric position of points over the textured surface are ' ...
,
reflection mapping
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. The texture is used to store the image of ...
,
specular mapping
Specularity is the visual appearance of specular reflections.
In computer graphics
In computer graphics, it means the quantity used in three-dimensional (3D) rendering which represents the amount of reflectivity a surface has. It is a key com ...
,
occlusion mapping, and many other variations on the technique (controlled by a
materials system
3D computer graphics, or “3D graphics,” sometimes called CGI, 3D-CGI or three-dimensional computer graphics are graphics that use a three-dimensional representation of geometric data (often Cartesian) that is stored in the computer for th ...
) have made it possible to simulate near-
photorealism
Photorealism is a genre of art that encompasses painting, drawing and other graphic media, in which an artist studies a photograph and then attempts to reproduce the image as realistically as possible in another medium. Although the term can be ...
in
real time
Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...
by vastly reducing the number of
polygon
In geometry, a polygon () is a plane figure that is described by a finite number of straight line segments connected to form a closed ''polygonal chain'' (or ''polygonal circuit''). The bounded plane region, the bounding circuit, or the two toge ...
s and lighting calculations needed to construct a realistic and functional 3D scene.
Texture maps
A is an image applied (mapped) to the surface of a shape or
polygon
In geometry, a polygon () is a plane figure that is described by a finite number of straight line segments connected to form a closed ''polygonal chain'' (or ''polygonal circuit''). The bounded plane region, the bounding circuit, or the two toge ...
. This may be a
bitmap image
In computing, a bitmap is a mapping from some domain (for example, a range of integers) to bits. It is also called a bit array or bitmap index.
As a noun, the term "bitmap" is very often used to refer to a particular bitmapping application: th ...
or a
procedural texture
In computer graphics, a procedural texture is a texture created using a mathematical description (i.e. an algorithm) rather than directly stored data. The advantage of this approach is low storage cost, unlimited texture resolution and easy textur ...
. They may be stored in common
image file formats
An Image file format is a file format for a digital image. There are many formats that can be used, such as JPEG, PNG, and GIF. Most formats up until 2022 were for storing 2D images, not 3D ones. The data stored in an image file format may be c ...
, referenced by
3d model formats or
material definitions, and assembled into
resource bundles
This is a list of file formats used by computers, organized by type. Filename extension it is usually noted in parentheses if they differ from the file format name or abbreviation. Many operating systems do not limit filenames to one extension s ...
.
They may have 1-3 dimensions, although 2 dimensions are most common for visible surfaces. For use with modern hardware, texture map data may be stored in
swizzled or tiled orderings to improve
cache coherency
In computer architecture, cache coherence is the uniformity of shared resource data that ends up stored in multiple local caches. When clients in a system maintain caches of a common memory resource, problems may arise with incoherent data, whi ...
.
Rendering APIs Rendering APIs typically provide just enough functionality to abstract a graphics accelerator, focussing on rendering primitives, state management, command lists/command buffers; and as such differ from fully fledged 3D graphics libraries, 3D engin ...
typically manage texture map resources (which may be located in
device memory) as buffers or surfaces, and may allow '
render to texture
This is a glossary of terms relating to computer graphics.
For more general computer hardware terms, see glossary of computer hardware terms.
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' for additional effects such as post processing or
environment mapping
In computer graphics
Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized a ...
.
They usually contain
RGB
The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three addi ...
color data (either stored as
direct color
Color depth or colour depth (see spelling differences), also known as bit depth, is either the number of bits used to indicate the color of a single pixel, or the number of bits used for each color component of a single pixel. When referring to ...
,
compressed formats, or
indexed color
In computing, indexed color is a technique to manage digital images' colors in a limited fashion, in order to save computer memory and file storage, while speeding up display refresh and file transfers. It is a form of vector quantization compr ...
), and sometimes an additional channel for
alpha blending
In computer graphics, alpha compositing or alpha blending is the process of combining one image with a background to create the appearance of partial or full transparency. It is often useful to render picture elements (pixels) in separate pas ...
(
RGBA
RGBA stands for red green blue alpha. While it is sometimes described as a color space, it is actually a three-channel RGB color model supplemented with a fourth ''alpha channel''. Alpha indicates how opaque each pixel is and allows an image to ...
) especially for
billboards
A billboard (also called a hoarding in the UK and many other parts of the world) is a large outdoor advertising structure (a billing board), typically found in high-traffic areas such as alongside busy roads. Billboards present large advertise ...
and ''decal'' overlay textures. It is possible to use the
alpha channel
In computer graphics, alpha compositing or alpha blending is the process of combining one image with a background to create the appearance of partial or full transparency. It is often useful to render picture elements (pixels) in separate pas ...
(which may be convenient to store in formats parsed by hardware) for other uses such as
specularity
Specularity is the visual appearance of specular reflections.
In computer graphics
In computer graphics, it means the quantity used in three-dimensional (3D) Rendering (computer graphics), rendering which represents the amount of Reflection co ...
.
Multiple texture maps (or
channels
Channel, channels, channeling, etc., may refer to:
Geography
* Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water.
Australia
* Channel Country, region of outback Austral ...
) may be combined for control over
specularity
Specularity is the visual appearance of specular reflections.
In computer graphics
In computer graphics, it means the quantity used in three-dimensional (3D) Rendering (computer graphics), rendering which represents the amount of Reflection co ...
,
normals,
displacement
Displacement may refer to:
Physical sciences
Mathematics and Physics
*Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...
, or
subsurface scattering
Subsurface scattering (SSS), also known as subsurface light transport (SSLT), is a mechanism of light transport in which light that penetrates the surface of a translucent object is scattered by interacting with the material and exits the surf ...
e.g. for skin rendering.
Multiple texture images may be combined in
texture atlases
In computer graphics, a texture atlas (also called a spritesheet or an image sprite in 2d computer graphics, 2d game development) is an image containing multiple smaller images, usually packed together to reduce overall dimensions. An atlas can con ...
or
array textures
This is a glossary of terms relating to computer graphics.
For more general computer hardware terms, see glossary of computer hardware terms.
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to reduce state changes for modern hardware. (They may be considered a modern evolution of
tile map graphics). Modern hardware often supports
cube map
In computer graphics, cube mapping is a method of environment mapping that uses the six faces of a cube as the map shape. The environment is projected onto the sides of a cube and stored as six square textures, or unfolded into six regions of a s ...
textures with multiple faces for environment mapping.
Creation
Texture maps may be acquired by
scanning/
digital photography
Digital photography uses cameras containing arrays of electronic photodetectors interfaced to an analog-to-digital converter (ADC) to produce images focused by a lens, as opposed to an exposure on photographic film. The digitized image is sto ...
, designed in
image manipulation software
In computer graphics, graphics software refers to a program or collection of programs that enable a person to manipulate images or models visually on a computer.
Computer graphics can be classified into two distinct categories: raster graphic ...
such as
GIMP
GIMP ( ; GNU Image Manipulation Program) is a free and open-source raster graphics editor used for image manipulation (retouching) and image editing, free-form drawing, transcoding between different image file formats, and more specialized task ...
,
Photoshop
Adobe Photoshop is a raster graphics editor developed and published by Adobe Inc. for Windows and macOS. It was originally created in 1988 by Thomas and John Knoll. Since then, the software has become the industry standard not only in raster ...
, or painted onto 3D surfaces directly in a
3D paint tool such as
Mudbox
Mudbox is a proprietary computer-based 3D sculpting and painting tool. developed by Autodesk, Mudbox was created by Skymatter, founded by Tibor Madjar, David Cardwell and Andrew Camenisch, former artists of Weta Digital, where it was first us ...
or
zbrush.
Texture application
This process is akin to applying patterned paper to a plain white box. Every vertex in a polygon is assigned a
texture coordinate (which in the 2d case is also known as
UV coordinate
This is a glossary of terms relating to computer graphics
Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and comp ...
s).
This may be done through explicit assignment of
vertex attributes
A vertex (plural vertices) in computer graphics is a data structure that describes certain attributes, like the position of a point in 2D or 3D space, or multiple points on a surface.
Application to 3D models
3D models are most often represente ...
, manually edited in a 3D modelling package through
UV unwrapping tools. It is also possible to associate a procedural transformation from 3d space to texture space with the
material
Material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties, or on their geologi ...
. This might be accomplished via
planar projection or, alternatively,
cylindrical
A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base.
A cylinder may also be defined as an infini ...
or
spherical
A sphere () is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. A sphere is the set of points that are all at the same distance from a given point in three-dimensional space.. That given point is the ce ...
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
In mathematics, an injective function (also known as injection, or one-to-one function) is a function that maps distinct elements of its domain to distinct elements; that is, implies . (Equivalently, implies in the equivalent contrapositiv ...
" mapping from every piece of a surface (which is important for
render mapping
This is a glossary of terms relating to computer graphics
Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and comp ...
and
light mapping, also known as
baking
Baking is a method of preparing food that uses dry heat, typically in an oven, but can also be done in hot ashes, or on hot stones. The most common baked item is bread but many other types of foods can be baked. Heat is gradually transferred " ...
).
Texture space
Texture mapping maps the model surface (or
screen space
This is a glossary of terms relating to computer graphics.
For more general computer hardware terms, see glossary of computer hardware terms.
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during rasterization) into texture space; in this space, the texture map is visible in its undistorted form.
UV unwrapping tools typically provide a view in texture space for manual editing of texture coordinates. Some rendering techniques such as
subsurface scattering
Subsurface scattering (SSS), also known as subsurface light transport (SSLT), is a mechanism of light transport in which light that penetrates the surface of a translucent object is scattered by interacting with the material and exits the surf ...
may be performed approximately by texture-space operations.
Multitexturing
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, and dirt maps may add weathering and variation; this can greatly reduce the apparent periodicity of repeating textures. Modern graphics may use more than 10 layers, which are combined using
shaders
In computer graphics, a shader is a computer program that calculates the appropriate levels of light, darkness, and color during the Rendering (computer graphics), rendering of a 3D scene - a process known as ''shading''. Shaders have evolved ...
, for greater fidelity. Another multitexture technique is
bump mapping
Bump mapping is a texture mapping technique in computer graphics for simulating bumps and wrinkles on the surface of an object. This is achieved by perturbing the surface normals of the object and using the perturbed normal during lighting cal ...
, which allows a texture to directly control the facing direction of a surface for the purposes of its lighting calculations; it can give a very good appearance of a complex surface (such as tree bark or rough concrete) that takes on lighting detail in addition to the usual detailed coloring. Bump mapping has become popular in recent video games, as graphics hardware has become powerful enough to accommodate it in real-time.
Texture filtering
The way that samples (e.g. when viewed as
pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the smal ...
s on the screen) are calculated from the
texel
Texel (; Texels dialect: ) is a municipality and an island with a population of 13,643 in North Holland, Netherlands. It is the largest and most populated island of the West Frisian Islands in the Wadden Sea. The island is situated north of De ...
s (texture pixels) is governed by
texture filtering
In computer graphics, texture filtering or texture smoothing is the method used to determine the texture color for a texture mapped pixel, using the colors of nearby texels (pixels of the texture). There are two main categories of texture filtering ...
. The cheapest method is to use the
nearest-neighbour interpolation, but
bilinear interpolation
In mathematics, bilinear interpolation is a method for interpolating functions of two variables (e.g., ''x'' and ''y'') using repeated linear interpolation. It is usually applied to functions sampled on a 2D rectilinear grid, though it can be ge ...
or
trilinear interpolation
Trilinear interpolation is a method of multivariate interpolation on a 3-dimensional regular grid. It approximates the value of a function at an intermediate point (x, y, z) within the local axial rectangular prism linearly, using function data on ...
between
mipmap
In computer graphics, mipmaps (also MIP maps) or pyramids are pre-calculated, optimized sequences of images, each of which is a progressively lower resolution representation of the previous. The height and width of each image, or level, in the m ...
s are two commonly used alternatives which reduce
aliasing
In signal processing and related disciplines, aliasing is an effect that causes different signals to become indistinguishable (or ''aliases'' of one another) when sampled. It also often refers to the distortion or artifact that results when a ...
or
jaggies
"Jaggies" is the informal name for artifacts in raster images, most frequently from aliasing, which in turn is often caused by non-linear mixing effects producing high-frequency components, or missing or poor anti-aliasing filtering prior to samp ...
. In the event of a texture coordinate being outside the texture, it is either
clamped or
wrapped.
Anisotropic filtering
In 3D computer graphics, anisotropic filtering (abbreviated AF) is a method of enhancing the image quality of textures on surfaces of computer graphics that are at oblique viewing angles with respect to the camera where the projection of the t ...
better eliminates directional artefacts when viewing textures from oblique viewing angles.
Texture streaming
Texture streaming is a means of using
data stream
In connection-oriented communication, a data stream is the transmission of a sequence of digitally encoded coherent signals to convey information. Typically, the transmitted symbols are grouped into a series of packets.
Data streaming has bec ...
s for textures, where each texture is available in two or more different resolutions, as to determine which texture should be loaded into memory and used based on draw distance from the viewer and how much memory is available for textures. Texture streaming allows for rendering engine to use low resolution textures for objects far away from the viewer's camera, and resolve those into more detailed textures, read from a data source, as the point of view nears the objects.
Baking
As an optimization, it is possible to render detail from a complex, high-resolution model or expensive process (such as
global illumination
Global illumination (GI), or indirect illumination, is a group of algorithms used in 3D computer graphics that are meant to add more realistic lighting to 3D scenes. Such algorithms take into account not only the light that comes directly from ...
) into a surface texture (possibly on a low-resolution model). ''Baking'' is also known as render mapping. This technique is most commonly used for
light maps, but may also be used to generate
normal maps and
displacement maps
Displacement mapping is an alternative computer graphics technique in contrast to bump, normal, and parallax mapping, using a texture or height map to cause an effect where the actual geometric position of points over the textured surface are ...
. Some computer games (e.g.
Messiah
In Abrahamic religions, a messiah or messias (; ,
; ,
; ) is a saviour or liberator of a group of people. The concepts of ''mashiach'', messianism, and of a Messianic Age originated in Judaism, and in the Hebrew Bible, in which a ''mashiach'' ...
) have used this technique. The original
Quake software engine used on-the-fly baking to combine light maps and colour maps ("
surface caching").
Baking can be used as a form of
level of detail generation, where a complex scene with many different elements and materials may be approximated by a ''single'' element with a ''single'' texture, which is then algorithmically reduced for lower rendering cost and fewer
drawcalls
Real-time computer graphics or real-time rendering is the sub-field of computer graphics focused on producing and analyzing images in real time. The term can refer to anything from rendering an application's graphical user interface (GUI) to ...
. It is also used to take high-detail models from
3D sculpting software and
point cloud scanning
Point or points may refer to:
Places
* Point, Lewis, a peninsula in the Outer Hebrides, Scotland
* Point, Texas, a city in Rains County, Texas, United States
* Point, the NE tip and a ferry terminal of Lismore, Inner Hebrides, Scotland
* Poin ...
and approximate them with
meshes
A mesh is a barrier made of connected strands of metal, fiber, or other flexible or ductile materials. A mesh is similar to a web or a net in that it has many attached or woven strands.
Types
* A plastic mesh may be extruded, oriented, ex ...
more suitable for realtime rendering.
Rasterisation algorithms
Various techniques have evolved in software and hardware implementations. Each offers different trade-offs in precision, versatility and performance.
Forward texture mapping
Some hardware systems e.g.
Sega Saturn
The is a home video game console developed by Sega and released on November 22, 1994, in Japan, May 11, 1995, in North America, and July 8, 1995, in Europe. Part of the fifth generation of video game consoles, it was the successor to the succ ...
and the
NV1
The Nvidia NV1, manufactured by SGS-Thomson Microelectronics under the model name STG2000, was a multimedia PCI card announced in May 1995 and released in November 1995. It was sold to retail by Diamond as the Diamond Edge 3D.
The NV1 feature ...
traverse texture coordinates directly, interpolating the projected position in screen space through texture space and splatting the texels into a
frame buffer
A framebuffer (frame buffer, or sometimes framestore) is a portion of random-access memory (RAM) containing a bitmap that drives a video display. It is a memory buffer containing data representing all the pixels in a complete video frame. Modern ...
. (in the case of the NV1, quadratic interpolation was used allowing curved rendering).
Sega
is a Japanese multinational corporation, multinational video game and entertainment company headquartered in Shinagawa, Tokyo. Its international branches, Sega of America and Sega Europe, are headquartered in Irvine, California and London, r ...
provided tools for
baking
Baking is a method of preparing food that uses dry heat, typically in an oven, but can also be done in hot ashes, or on hot stones. The most common baked item is bread but many other types of foods can be baked. Heat is gradually transferred " ...
suitable per-quad texture tiles from UV mapped models.
This has the advantage that texture maps are read in a simple linear fashion.
Forward texture mapping may also sometimes produce more natural looking results than affine texture mapping if the
primitives are aligned with prominent texture directions (e.g. road markings or layers of bricks). This provides a limited form of perspective correction. However, perspective distortion is still visible for primitives near the camera (e.g. the Saturn port of ''
Sega Rally
''Sega Rally'' is a series of racing video games published by Sega and developed by several studios including Sega AM3, Sega and Sega Racing Studio.
The series released its first title, ''Sega Rally Championship'' in 1994. Initially, ''Sega Rall ...
'' exhibited texture-squashing artifacts as nearby polygons were
near clipped
Clipping, in the context of computer graphics, is a method to selectively enable or disable rendering operations within a defined region of interest. Mathematically, clipping can be described using the terminology of constructive geometry. A ...
without UV coordinates).
This technique is not used in modern hardware because
UV coordinates
UV mapping is the 3D modeling process of projecting a 3D model's surface to a 2D image for texture mapping. The letters "U" and "V" denote the axes of the 2D texture because "X", "Y", and "Z" are already used to denote the axes of the 3D object i ...
have proved more versatile for modelling and more consistent for
clipping
Clipping may refer to:
Words
* Clipping (morphology), the formation of a new word by shortening it, e.g. "ad" from "advertisement"
* Clipping (phonetics), shortening the articulation of a speech sound, usually a vowel
* Clipping (publications) ...
.
Inverse texture mapping
Most approaches use inverse texture mapping, which traverses the
rendering primitives
Rendering or image synthesis is the process of generating a photorealistic or non-photorealistic image from a 2D or 3D model by means of a computer program. The resulting image is referred to as the render. Multiple models can be defined ...
in screen space whilst interpolating texture coordinates for sampling. This interpolation may be ''affine'' or ''perspective correct''. One advantage is that each output pixel is guaranteed to only be traversed once; generally the source texture map data is stored in some lower bit-depth or compressed form whilst the frame buffer uses a higher bit-depth. Another is greater versatility for
UV mapping
UV mapping is the 3D modeling process of projecting a 3D model's surface to a 2D image for texture mapping. The letters "U" and "V" denote the axes of the 2D texture because "X", "Y", and "Z" are already used to denote the axes of the 3D object i ...
. A
texture cache
This is a glossary of terms relating to computer graphics.
For more general computer hardware terms, see glossary of computer hardware terms.
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becomes important for buffering reads, since the
memory access pattern In computing, a memory access pattern or IO access pattern is the pattern with which a system or program reads and writes memory on secondary storage. These patterns differ in the level of locality of reference and drastically affect cache performa ...
in
texture space
Texture mapping is a method for mapping a texture on a computer-generated graphic. Texture here can be high frequency detail, surface texture, or color.
History
The original technique was pioneered by Edwin Catmull in 1974.
Texture mappi ...
is more complex.
Affine texture mapping
![Perspective correct texture mapping](https://upload.wikimedia.org/wikipedia/commons/7/7d/Perspective_correct_texture_mapping.svg)
Affine texture mapping linearly interpolates texture coordinates across a surface, and so is the fastest form of texture mapping. Some software and hardware (such as the original
PlayStation
is a video gaming brand that consists of five home video game consoles, two handhelds, a media center, and a smartphone, as well as an online service and multiple magazines. The brand is produced by Sony Interactive Entertainment, a divisi ...
)
project
A project is any undertaking, carried out individually or collaboratively and possibly involving research or design, that is carefully planned to achieve a particular goal.
An alternative view sees a project managerially as a sequence of even ...
vertices in 3D space onto the screen during rendering and
linearly interpolate the texture coordinates ''in screen space'' between them ("inverse texture mapping"). This may be done by incrementing
fixed point UV coordinates
UV mapping is the 3D modeling process of projecting a 3D model's surface to a 2D image for texture mapping. The letters "U" and "V" denote the axes of the 2D texture because "X", "Y", and "Z" are already used to denote the axes of the 3D object i ...
, or by an
incremental error algorithm
This is a glossary of terms relating to computer graphics.
For more general computer hardware terms, see glossary of computer hardware terms.
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akin to
Bresenham's line algorithm
Bresenham's line algorithm is a line drawing algorithm that determines the points of an ''n''-dimensional raster that should be selected in order to form a close approximation to a straight line between two points. It is commonly used to draw line ...
.
In contrast to perpendicular polygons, this leads to noticeable distortion with perspective transformations (see figure: the checker box texture appears bent), especially as primitives near the
camera
A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...
. Such distortion may be reduced with the subdivision of the polygon into smaller ones.
Perspective correctness
Perspective correct texturing accounts for the vertices' positions in 3D space, rather than simply interpolating coordinates in 2D screen space.
This achieves the correct visual effect but it is more expensive to calculate.
To perform perspective correction of the texture coordinates
and
, with
being the depth component from the viewer's point of view, we can take advantage of the fact that the values
,
, and
are linear in screen space across the surface being textured. In contrast, the original
,
and
, before the division, are not linear across the surface in screen space. We can therefore linearly interpolate these reciprocals across the surface, computing corrected values at each pixel, to result in a perspective correct texture mapping.
To do this, we first calculate the reciprocals at each vertex of our geometry (3 points for a triangle). For vertex
we have
. Then, we linearly interpolate these reciprocals between the
vertices (e.g., using
Barycentric Coordinates
In mathematics, an affine space is a geometric structure that generalizes some of the properties of Euclidean spaces in such a way that these are independent of the concepts of distance and measure of angles, keeping only the properties related ...
), resulting in interpolated values across the surface. At a given point, this yields the interpolated
, and
. Note that this
cannot be yet used as our texture coordinates as our division by
altered their coordinate system.
To correct back to the
space we first calculate the corrected
by again taking the reciprocal
. Then we use this to correct our
:
and
.
This correction makes it so that in parts of the polygon that are closer to the viewer the difference from pixel to pixel between texture coordinates is smaller (stretching the texture wider) and in parts that are farther away this difference is larger (compressing the texture).
:Affine texture mapping directly interpolates a texture coordinate
between two endpoints
and
:
::
where
:Perspective correct mapping interpolates after dividing by depth
, then uses its interpolated reciprocal to recover the correct coordinate:
::
3D graphics hardware typically supports perspective correct texturing.
Various techniques have evolved for rendering texture mapped geometry into images with different quality/precision tradeoffs, which can be applied to both software and hardware.
Classic software texture mappers generally did only simple mapping with at most one lighting effect (typically applied through a
lookup table
In computer science, a lookup table (LUT) is an array that replaces runtime computation with a simpler array indexing operation. The process is termed as "direct addressing" and LUTs differ from hash tables in a way that, to retrieve a value v wi ...
), and the perspective correctness was about 16 times more expensive.
Restricted camera rotation
The ''
Doom engine
id Tech 1, also known as the ''Doom'' engine, is the game engine that powers the id Software games ''Doom'' and '' Doom II: Hell on Earth''. It is also used in ''Heretic'', '' Hexen: Beyond Heretic'', '' Strife: Quest for the Sigil'', '' Hacx: T ...
'' restricted the world to vertical walls and horizontal floors/ceilings, with a camera that could only rotate about the vertical axis. This meant the walls would be a constant depth coordinate along a vertical line and the floors/ceilings would have a constant depth along a horizontal line. A fast affine mapping could be used along those lines because it would be correct. Some later renderers of this era simulated a small amount of camera
pitch with
shearing
Sheep shearing is the process by which the woollen fleece of a sheep is cut off. The person who removes the sheep's wool is called a '' shearer''. Typically each adult sheep is shorn once each year (a sheep may be said to have been "shorn" or ...
which allowed the appearance of greater freedom whilst using the same rendering technique.
Some engines were able to render texture mapped
Heightmaps
In computer graphics, a heightmap or heightfield is a raster image used mainly as Discrete Global Grid in secondary elevation modeling. Each pixel stores values, such as surface elevation data, for display in 3D computer graphics. A heightm ...
(e.g.
Nova Logic's
Voxel Space
Voxel Space was a voxel raster graphics rendering engine invented by Novalogic developer and vice-president of technology, Kyle Freeman. The company was issued a patent for the technology in early 2000.
History
The original Voxel Space engine w ...
, and the engine for
Outcast) via
Bresenham
Jack Elton Bresenham (born 11 October 1937, Clovis, New Mexico, US) is a former professor of computer science.
Biography
Bresenham retired from 27 years of service at IBM as a Senior Technical Staff Member in 1987. He taught for 16 years at Wint ...
-like incremental algorithms, producing the appearance of a texture mapped landscape without the use of traditional geometric primitives.
Subdivision for perspective correction
Every triangle can be further subdivided into groups of about 16 pixels in order to achieve two goals. First, keeping the arithmetic mill busy at all times. Second, producing faster arithmetic results.
World space subdivision
For perspective texture mapping without hardware support, a triangle is broken down into smaller triangles for rendering and affine mapping is used on them. The reason this technique works is that the distortion of affine mapping becomes much less noticeable on smaller polygons. The
Sony PlayStation
is a video gaming brand that consists of five home video game consoles, two handhelds, a media center, and a smartphone, as well as an online service and multiple magazines. The brand is produced by Sony Interactive Entertainment, a divi ...
made extensive use of this because it only supported affine mapping in hardware but had a relatively high triangle throughput compared to its peers.
Screen space subdivision
Software renderers generally preferred screen subdivision because it has less overhead. Additionally, they try to do linear interpolation along a line of pixels to simplify the set-up (compared to 2d affine interpolation) and thus again the overhead (also affine texture-mapping does not fit into the low number of registers of the
x86
x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introd ...
CPU; the
68000
The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector ...
or any
RISC
In computer engineering, a reduced instruction set computer (RISC) is a computer designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a complex instruction set comput ...
is much more suited).
A different approach was taken for ''
Quake'', which would calculate perspective correct coordinates only once every 16 pixels of a scanline and linearly interpolate between them, effectively running at the speed of linear interpolation because the perspective correct calculation runs in parallel on the co-processor. The polygons are rendered independently, hence it may be possible to switch between spans and columns or diagonal directions depending on the orientation of the
polygon normal
In geometry, a normal is an object such as a line, ray, or vector that is perpendicular to a given object. For example, the normal line to a plane curve at a given point is the (infinite) line perpendicular to the tangent line to the curve at ...
to achieve a more constant z but the effort seems not to be worth it.
Other techniques
Another technique was approximating the perspective with a faster calculation, such as a polynomial. Still another technique uses 1/z value of the last two drawn pixels to linearly extrapolate the next value. The division is then done starting from those values so that only a small remainder has to be divided but the amount of bookkeeping makes this method too slow on most systems.
Finally,
the Build engine extended the constant distance trick used for Doom by finding the line of constant distance for arbitrary polygons and rendering along it.
Hardware implementations
Texture mapping hardware was originally developed for simulation (e.g. as implemented in the
Evans and Sutherland
Evans & Sutherland is a pioneering American computer firm in the computer graphics field. Its current products are used in digital projection environments like planetariums. Its simulation business, which it sold to Rockwell Collins, sold produc ...
ESIG image generators), and professional
graphics workstations such as
Silicon Graphics
Silicon Graphics, Inc. (stylized as SiliconGraphics before 1999, later rebranded SGI, historically known as Silicon Graphics Computer Systems or SGCS) was an American high-performance computing manufacturer, producing computer hardware and soft ...
, broadcast
digital video effect
Digital video effects (DVEs) are visual effects that provide comprehensive live video image manipulation, in the same form as optical printer effects in film. DVEs differ from standard video switcher effects (often referred to as ''analog effects' ...
s machines such as the
Ampex ADO and later appeared in
Arcade cabinet
An arcade cabinet, also known as an arcade machine or a coin-op cabinet or coin-op machine, is the housing within which an arcade game's electronic hardware resides. Most cabinets designed since the mid-1980s conform to the Japanese Amusement Ma ...
s, consumer
video game console
A video game console is an electronic device that Input/output, outputs a video signal or image to display a video game that can be played with a game controller. These may be home video game console, home consoles, which are generally placed i ...
s, and PC
video card
A graphics card (also called a video card, display card, graphics adapter, VGA card/VGA, video adapter, display adapter, or mistakenly GPU) is an expansion card which generates a feed of output images to a display device, such as a computer moni ...
s in the mid 1990s. In
flight simulation
A flight simulator is a device that artificially re-creates aircraft flight and the environment in which it flies, for pilot training, design, or other purposes. It includes replicating the equations that govern how aircraft fly, how they rea ...
, texture mapping provided important motion cues.
Modern
graphics processing unit
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, mobi ...
s (GPUs) provide specialised
fixed function units called ''texture samplers'', or
''texture mapping units'', to perform texture mapping, usually with
trilinear filtering
Trilinear filtering is an extension of the bilinear texture filtering method, which also performs linear interpolation between mipmaps.
Bilinear filtering has several weaknesses that make it an unattractive choice in many cases: using it on a f ...
or better multi-tap
anisotropic filtering
In 3D computer graphics, anisotropic filtering (abbreviated AF) is a method of enhancing the image quality of textures on surfaces of computer graphics that are at oblique viewing angles with respect to the camera where the projection of the t ...
and hardware for decoding specific formats such as
DXTn. As of 2016, texture mapping hardware is ubiquitous as most
SOCs contain a suitable GPU.
Some hardware combines texture mapping with
hidden-surface determination
In 3D computer graphics, hidden-surface determination (also known as shown-surface determination, hidden-surface removal (HSR), occlusion culling (OC) or visible-surface determination (VSD)) is the process of identifying what surfaces and parts o ...
in
tile based deferred rendering Tiled rendering is the process of subdividing a computer graphics image by a regular grid in optical space and rendering each section of the grid, or ''tile'', separately. The advantage to this design is that the amount of memory and bandwidth is re ...
or
scanline rendering
Scanline rendering (also scan line rendering and scan-line rendering) is an algorithm for visible surface determination, in 3D computer graphics, that works on a row-by-row basis rather than a polygon-by-polygon or pixel-by-pixel basis. All of t ...
; such systems only fetch the visible
texels at the expense of using greater workspace for transformed vertices. Most systems have settled on the
Z-buffering
A depth buffer, also known as a z-buffer, is a type of data buffer used in computer graphics to represent depth information of objects in 3D space from a particular perspective. Depth buffers are an aid to rendering a scene to ensure that the ...
approach, which can still reduce the texture mapping workload with front-to-back
sorting
Sorting refers to ordering data in an increasing or decreasing manner according to some linear relationship among the data items.
# ordering: arranging items in a sequence ordered by some criterion;
# categorizing: grouping items with similar pro ...
.
Applications
Beyond 3D rendering, the availability of texture mapping hardware has inspired its use for accelerating other tasks:
Tomography
It is possible to use texture mapping hardware to accelerate both the
reconstruction
Reconstruction may refer to:
Politics, history, and sociology
*Reconstruction (law), the transfer of a company's (or several companies') business to a new company
*'' Perestroika'' (Russian for "reconstruction"), a late 20th century Soviet Unio ...
of
voxel
In 3D computer graphics, a voxel represents a value on a regular grid in three-dimensional space. As with pixels in a 2D bitmap, voxels themselves do not typically have their position (i.e. coordinates) explicitly encoded with their values. Ins ...
data sets from
tomographic scans, and to
visualize the results
User interfaces
Many user interfaces use texture mapping to accelerate animated transitions of screen elements, e.g.
Exposé
Expose, exposé, or exposed may refer to:
News sources
* Exposé (journalism), a form of investigative journalism
* '' The Exposé'', a British conspiracist website
Film and TV Film
* ''Exposé'' (film), a 1976 thriller film
* ''Exposed'' (1932 ...
in
Mac OS X
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac (computer), Mac computers. Within the market of ...
.
See also
*
2.5D
*
3D computer graphics
3D computer graphics, or “3D graphics,” sometimes called CGI, 3D-CGI or three-dimensional computer graphics are graphics that use a three-dimensional representation of geometric data (often Cartesian) that is stored in the computer for th ...
*
Mipmap
In computer graphics, mipmaps (also MIP maps) or pyramids are pre-calculated, optimized sequences of images, each of which is a progressively lower resolution representation of the previous. The height and width of each image, or level, in the m ...
*
Materials system
3D computer graphics, or “3D graphics,” sometimes called CGI, 3D-CGI or three-dimensional computer graphics are graphics that use a three-dimensional representation of geometric data (often Cartesian) that is stored in the computer for th ...
*
Parametrization
*
Texture synthesis
Texture synthesis is the process of algorithmically constructing a large digital image from a small digital sample image by taking advantage of its structural content. It is an object of research in computer graphics and is used in many fields, amo ...
*
Texture atlas
In computer graphics, a texture atlas (also called a spritesheet or an image sprite in 2d game development) is an image containing multiple smaller images, usually packed together to reduce overall dimensions. An atlas can consist of uniformly-siz ...
*
Texture splatting In computer graphics, texture splatting is a method for combining different textures. It works by applying an alphamap (also called a "weightmap" or a "splat map") to the higher levels, thereby revealing the layers underneath where the alphamap is ...
– a technique for combining textures
*
Shader (computer graphics)
In computer graphics, a shader is a computer program that calculates the appropriate levels of light, darkness, and color during the rendering of a 3D scene - a process known as ''shading''. Shaders have evolved to perform a variety of spec ...
References
Software
TexRecon— open-source software for texturing 3D models written in C++
External links
Introduction into texture mapping using C and SDL(PDF)
Programming a textured terrainusing XNA/DirectX, from www.riemers.net
Time TexturingTexture mapping with bezier lines
Polynomial Texture MappingInteractive Relighting for Photos
Methods that can be used to interpolate a texture knowing the texture coords at the vertices of a polygon
3D Texturing Tools
{{DEFAULTSORT:Texture Mapping
Computer graphics