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Viviparity
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An aphid giving viviparous birth, an unusual mode of reproduction among insects
Not to be confused with vivipary.
Among animals, viviparity is development of the embryo inside the body of the parent, eventually leading to live birth, as opposed to reproduction by laying eggs that complete their incubation outside the parental body.
Viviparity and the adjective viviparous derive from Latin vivus ("living") and parire ("to bear young").[1]
Contents
1 Reproductive mode
2 Evolution
3 References
4 See also
Reproductive mode[edit]
Hemotrophic viviparity: a mammal embryo (centre) attached by its umbilical cord to a placenta (top) which provides food
Further information: Modes of reproduction
Five modes of reproduction have been differentiated in animals[2] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[3] These modes are distinguished from viviparity, which covers all the modes that result in live birth:
Histotrophic viviparity: the zygotes develop in the female’s oviducts, but find their nutriments by oophagy or adelphophagy (intra-uterine cannibalism of eggs or sibling embryos in some sharks or in the black salamander Salamandra atra).
Hemotrophic viviparity: nutrients are provided by the female, often through some form of placenta. In the frog Gastrotheca ovifera, embryos are fed by the mother through specialized gills. The skink Pseudemoia entrecasteauxii and most mammals exhibit a hemotrophic viviparity.
Placental viviparity is arguably the most highly developed form of viviparity. Placental mammals, including humans, are the best-known example, but adaptations in some other animals also have incorporated this principle or close analogies. Other examples include some species of scorpions[4] and cockroaches,[5][6] certain genera of sharks and snakes, and velvet worms.
Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[3]
At least some transport of nutrients from mother to embryo appears to be common to all viviparous species, but those with fully developed placentas such as found in the Theria, some skinks, and some fish can rely on the placenta for transfer of all necessary nutrients to the offspring and for removal of all the metabolic wastes as well once it has been fully established during the early phases of a pregnancy. In such species, there is direct, intimate contact between maternal and embryonic tissue, though there also is a placental barrier to control or prevent uncontrolled exchange and the transfer of pathogens.
In at least one species of skink in the large genus Trachylepis, placental transport accounts for nearly all of the provisioning of nutrients to the embryos before birth. In the uterus, the eggs are very small, about 1mm in diameter, with very little yolk and very thin shells. The shell membrane is vestigial and transient; its disintegration permits the absorption of nutrients from uterine secretions. The embryo then produces invasive chorionic tissues that grow between the cells of the uterine lining till they can absorb nutrients from maternal blood vessels. As it penetrates the lining, the embryonic tissue grows aggressively till it forms sheets of tissue beneath the uterine epithelium. They eventually strip it away and replace it, making direct contact with maternal capillaries. In several respects, the phenomenon is of considerable importance in theoretical zoology. The authors remark that such an endotheliochorial placenta is fundamentally different from that of any known viviparous reptile.[7]
There is no relationship between sex-determining mechanisms and whether a species bears live young or lays eggs. Temperature-dependent sex determination, which cannot function in an aquatic environment, is seen only in terrestrial viviparous reptiles. Therefore, marine viviparous species, including sea snakes and, it now appears, the mosasaurs, ichthyosaurs, and plesiosaurs of the Cretaceous, use genotypic sex determination (sex chromosomes), much as birds and mammals do.[8] Genotypic sex determination is also found in most reptiles, including many viviparous ones (such as Pseudemoia entrecasteauxii), whilst temperature dependent sex determination is found in some viviparous species, such as the montane water skink (Eulamprus tympanum).[9]
Evolution[edit]
In general, viviparity and matrotrophy are believed to have evolved from an ancestral condition of oviparity and lecithotrophy (nutrients supplied through the yolk).[10] One traditional hypothesis concerning the sequence of evolutionary steps leading to viviparity is a linear model. According to such a model, provided that fertilization was internal, the egg might have been retained for progressively longer periods in the reproductive tract of the mother. Through continued generations of egg retention, viviparous lecithotrophy may have gradually developed; in other words the entire development of the embryo, though still with nutrients provided by the yolk, occurred inside the mother’s reproductive tract, after which she would give birth to the young as they hatched. The next evolutionary development would be incipient matrotrophy, in which yolk supplies are gradually reduced and are supplemented with nutrients from the mother's reproductive tract.[11]
In many ways, depending on the ecology and life strategy of the species, viviparity may be more strenuous and more physically and energetically taxing on the mother than oviparity. However, its numerous evolutionary origins imply that in some scenarios there must be worthwhile benefits to viviparous modes of reproduction; selective pressures have led to its convergent evolution more than 150 times among the vertebrates alone.[12]
There is no one mode of reproduction that is universally superior in selective terms, but in many circumstances viviparity of various forms offers good protection from parasites and predators and permits flexibility in dealing with problems of reliability and economy in adverse circumstances. Variations on the theme in biology are enormous, ranging from trophic eggs to resorption of partly developed embryos in hard times or when they are too numerous for the mother to bring to term, but among the most profoundly advantageous features of viviparity are various forms of physiological support and protection of the embryo, such as thermoregulation and osmoregulation.[13] Since the developing offspring remains within the mother’s body, she becomes, in essence, a walking incubator, protecting the developing young from excessive heat, cold, drought, or flood. This offers powerful options for dealing with excessive changes in climate or when migration events expose populations to unfavourable temperatures or humidities. In squamate reptiles in particular, there is a correlation between high altitudes or latitudes, colder climates and the frequency of viviparity. The idea that the tendency to favour egg-retention selectively under cooler conditions arises from the thermoregulatory benefits, and that it consequently promotes the evolution of viviparity as an adaptation, is known as "the cold climate hypothesis".[14]
References[edit]
Jump up ^ "viviparous (adj.)". Online Etymology Dictionary. Retrieved 6 April 2018.
Jump up ^ Lodé, Thierry (2001). Les stratégies de reproduction des animaux (Reproduction strategies in the animal kingdom). Eds Dunod Sciences, Paris.
^ Jump up to: a b Blackburn, D. G. (2000). Classification of the reproductive patterns of amniotes.:" Herpetological Monographs", 371-377.
Jump up ^ Capinera, John L., Encyclopedia of entomology. Springer Reference, 2008, p. 3311.
Jump up ^ Costa, James T., The Other Insect Societies. Belknap Press, 2006, p. 151.
Jump up ^ Newbern, E. (2016-01-26). "Mom Genes: This Cockroach Species' Live Births Are in Its DNA". LiveScience. Purch. Retrieved 2016-01-26.
Jump up ^ Blackburn, D. G.; Flemming, A. F. (2011). "Invasive implantation and intimate placental associations in a placentotrophic african lizard, Trachylepis ivensi (scincidae)". Journal of Morphology. 273: 137–159. doi:10.1002/jmor.11011. PMID 21956253.
Jump up ^ Organ, Chris L.; et al. (2009). "Genotypic sex determination enabled adaptive radiations of extinct marine reptiles". Nature. 461: 389–392. doi:10.1038/nature08350. PMID 19759619. CS1 maint: Explicit use of et al. (link)
Jump up ^ Robert, Kylie A.; Thompson, Michael B. (2001). "Sex determination: viviparous lizard selects sex of embryos". Nature. 412 (6848): 698–699. doi:10.1038/35089135. PMID 11507628.
Jump up ^ Griffith, OW; Blackburn, DG; Brandley, MC; Van Dyke, JU; Whittington, CW; Thompson, M.B. (2015). "Ancestral state reconstructions require biological evidence to test evolutionary hypotheses: A case study examining the evolution of reproductive mode in squamate reptiles". J Exp Zool Part B. 324: 493–503. doi:10.1002/jez.b.22614.
Jump up ^ Blackburn, D. G. (1992). "Convergent evolution of viviparity, matrotrophy, and specializations for fetal nutrition in reptiles and other vertebrates". Am. Zool. 32: 313–321. doi:10.1093/icb/32.2.313.
Jump up ^ Blackburn, Daniel G. "Evolution of vertebrate viviparity and specializations for fetal nutrition: A quantitative and qualitative analysis". Journal of Morphology. 276: 961–990. doi:10.1002/jmor.20272.
Jump up ^ Blackburn, D. G. (1999). Viviparity and oviparity: evolution and reproductive strategies. Encyclopedia of Reproduction. Academic Press, New York, New York, USA, 994-1003
Jump up ^ Lambert, S. M.; Wiens, J. J. (2013). "Evolution of viviparity: a phylogenetic test of the cold-climate hypothesis in phrynosomatid lizards". Evolution. 67: 2614–2630. doi:10.1111/evo.12130. PMID 24033171.
Wang, Y; Evans, SE (2011). "A gravid lizard from the Cretaceous of China and the early history of squamate viviparity". Naturwissenschaften. 98: 739–743. doi:10.1007/s00114-011-0820-1. PMID 21766177.
See also[edit]
Apomixis
Placental mammals
Marsupials
Live-bearing aquarium fish
False vivipary
hide
v
t
e
Modes of reproduction
Modes
Oviparity
Ovuliparity
Viviparity (Histotrophic, Hemotrophic)
Ovoviviparity
Fertilization
External fertilization
Internal fertilization
Parental care
birds
fish (mouthbrooding)
humans
mammals
Related topics
Adelphophagy
Gastric-brooding frog
Live-bearing aquarium fish
Male pregnancy
Matrotrophy
Oophagy
Pregnancy in fish
Trophic egg
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Return address
From Wikipedia, the free encyclopedia
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For other uses, see Return address (disambiguation).
Envelope with return address in top left corner
In postal mail, a return address is an explicit inclusion of the address of the person sending the message. It provides the recipient (and sometimes authorized intermediaries) with a means to determine how to respond to the sender of the message if needed. The return address need not include a sender's name, but should include address or P.O. box details in the same way as the delivery address should. In some countries, the return address is conventionally located in the upper left hand corner of the envelope, card, or label. In the United Kingdom, the return address is usually placed on the reverse of the envelope, near the top.[1]
Businesses often use envelopes preprinted with a return address. Many individuals have sheets of adhesive labels preprinted with their home address to affix to their correspondence. Charities sometimes include such sheets in mailshots. Rolls of Return Address Labels can be purchased from companies that sell personalized labels to provide individuals an easy way to peel and stick return address labels to their envelopes.
The return address is not required on postal mail. However, lack of a return address prevents the postal service from being able to return the item if it proves undeliverable; such as from damage, postage due, or invalid destination. Such mail may otherwise become dead letter mail.[2]
Should the return address be of a different state or country, the mail may be routed through that location for ease of return.
History[edit]
The return address has been used on U. S. postage since the 1880s. As pressure printing became more commonplace during the early 1900s, labels became cheaper and more easily distributed. The profession involved with producing these labels was known as lithography. During the 1950s in the United States, more and more mail was not arriving at intended recipients, and as a result of the lack of a return address, said mail ended up in the dead letter office. With this rise in dead mail, the post office pleaded for people to use a return address. Even after this, the public still tended to neglect adding a return address. This prompted the postmaster to inform the public that mail without a return address would be less of a priority than mail with a return address. Still, the public did not widely use a return address until the 1960s when companies began to offer deals for preprinted return labels such as 2,500 labels for $2.00. They became more popular with the invention of label dispensers. With the invention of the personal computer, software enabled people to print their own labels. As e-mail began to overtake written mail, the return address became automatic in an e-mail.[3]
References[edit]
Jump up ^ Conventional Positioning of Return Address Labels in the UK: http://thelabelroom.co.uk/blogo/wordpress/?p=48
Jump up ^ "Business Mail 101". United States Postal Service Website. Retrieved 23 August 2013.
Jump up ^ "The History of Return Address Labels!". Web page. Retrieved 23 August 2013.
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Verstehen
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Verstehen (German pronunciation: [fɛɐˈʃteːən], literally: "to understand") in the context of German philosophy and social sciences in general, has been used since the late 19th century – in English as in German – with the particular sense of the "interpretive or participatory" examination of social phenomena.[1] The term is closely associated with the work of the German sociologist, Max Weber, whose antipositivism established an alternative to prior sociological positivism and economic determinism, rooted in the analysis of social action.[2] In anthropology, Verstehen has come to mean a systematic interpretive process in which an outside observer of a culture attempts to relate to it and understand others.
Verstehen is now seen as a concept and a method central to a rejection of positivistic social science (although Weber appeared to think that the two could be united). Verstehen refers to understanding the meaning of action from the actor's point of view. It is entering into the shoes of the other, and adopting this research stance requires treating the actor as a subject, rather than an object of your observations. It also implies that unlike objects in the natural world human actors are not simply the product of the pulls and pushes of external forces. Individuals are seen to create the world by organizing their own understanding of it and giving it meaning. To do research on actors without taking into account the meanings they attribute to their actions or environment is to treat them like objects.[3]
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1 Meaning
2 Dilthey and hermeneutics
3 Weber and the social sciences
4 Criticism
5 See also
6 References
7 External links
Meaning[edit]
Interpretative sociology (verstehende Soziologie) is the study of society that concentrates on the meanings people associate to their social world.[4] Interpretative sociology strives to show that reality is constructed by people themselves in their daily lives.[5]
Verstehen roughly translates to "meaningful understanding" or "putting yourself in the shoes of others to see things from their perspective". Interpretive sociology differs from positivist sociology in three ways:
Interpretive sociology deals with the meaning attached to behavior, unlike positivist sociology which focuses on action.
Interpretive sociology sees reality as being constructed by people, unlike positivist sociology which sees an objective reality "out there".
Interpretive sociology relies on qualitative data, unlike positivist sociology which tends to make use of quantitative data.[6]
Dilthey and hermeneutics[edit]
Verstehen was introduced into philosophy and the human sciences (Geisteswissenschaften) by the German historist philosopher Johann Gustav Droysen. He first made a distinction between nature and history in terms of the categories of space and time. The method of the natural sciences (Naturwissenschaften) is explanation (erklären), while that of history is understanding (verstehen).[7][8][9][10]
The concept of Verstehen was later used by the German philosopher Wilhelm Dilthey[11][12] to describe the first-person participatory perspective that agents have on their individual experience as well as their culture, history, and society. In this sense, it is developed in the context of the theory and practice of interpretation (as understood in the context of hermeneutics) and contrasted with the external objectivating third-person perspective of explanation (das Erklären) in which human agency, subjectivity, and its products are analyzed as effects of impersonal natural forces in the natural sciences and social structures in sociology.
Twentieth-century philosophers such as Martin Heidegger and Hans-Georg Gadamer[13] have been critical of what they considered to be the romantic and subjective character of Verstehen in Dilthey, although both Dilthey and the early Heidegger were interested in the "facticity" and "life-context" of understanding, and sought to universalize it as the way humans exist through language on the basis of ontology.[14][15] Verstehen also played a role in Edmund Husserl and Alfred Schutz's analysis of the "lifeworld." Jürgen Habermas and Karl-Otto Apel further transformed the concept of Verstehen, reformulating it on the basis of a transcendental-pragmatic philosophy of language and the theory of communicative action.
Weber and the social sciences[edit]
Max Weber and Georg Simmel[16] introduced interpretive understanding (Verstehen) into sociology, where it has come to mean a systematic interpretive process in which an outside observer of a culture (such as an anthropologist or sociologist) relates to an indigenous people or sub-cultural group on their own terms and from their own point of view, rather than interpreting them in terms of his or her own culture.[17] Verstehen can mean either a kind of empathic or participatory understanding of social phenomena. In anthropological terms this is sometimes described as cultural relativism, especially by those that have a tendency to argue toward universal ideals. In sociology it is an aspect of the comparative-historical approach, where the context of a society like twelfth century "France" can be potentially better understood (Besserverstehen) by the sociologist than it could have been by people living in a village in Burgundy. It relates to how people in life give meaning to the social world around them and how the social scientist accesses and evaluates this "first-person perspective". This concept has been both expanded and criticized by later social scientists. Proponents laud this concept as the only means by which researchers from one culture can examine and explain behaviors in another. While the exercise of Verstehen has been more popular among social scientists in Europe, such as Habermas, Verstehen was introduced into the practice of sociology in the United States by Talcott Parsons, an American follower of Max Weber. Parsons used his structural functionalism to incorporate this concept into his 1937 work, The Structure of Social Action.[18]
Weber had more specific beliefs than Marx where he put value to understanding and meaning of key elements—not just with intuition or sympathy with the individual but also the product of "systematic and rigorous research". The goal is to identify human actions and interpreting them as observable events leading us to believe that it not only provides for a good explanation for individual actions but also for group interactions. The meaning attached needs to include constraints and limitations and analyze the motivation for action. Weber believed that this gives the sociologist an advantage over a natural scientist because "We can accomplish something which is never attainable in the natural sciences, namely the subjective understanding of the action of the component individuals" (Weber, Economy and Society, p. 15).[19]
Criticism[edit]
Critics of the social scientific concept of Verstehen such as Mikhail Bakhtin and Dean MacCannell counter that it is simply impossible for a person born of one culture to ever completely understand another culture, and that it is arrogant and conceited to attempt to interpret the significance of one culture's symbols through the terms of another (supposedly superior) culture.[citation needed] Such criticisms do not necessarily allow for the possibility that Verstehen does not involve "complete" understanding.[citation needed] Just as in physical science all knowledge is asymptotic to the full explanation, a high degree of cross-cultural understanding is very valuable. The opposite of Verstehen would seem to be ignorance of all but that which is immediately observable, meaning that we would not be able to understand any time and place but our own. A certain level of interpretive understanding is necessary for our own cultural setting, however, and it can easily be argued that even the full participant in a culture does not fully understand it in every regard.[citation needed]
Critics also believe that it is the sociologist's job to not just observe people and what people do but also share in their world of meaning and come to appreciate why they act as they do. Subjective thoughts and feelings regarded as bias in the sciences is an important aspect to be controlled for while doing sociological research.[20]
See also[edit]
Sociology portal
Antinaturalism (sociology)
Emic and etic
Humanistic sociology
Humanistic coefficient
Nomothetic and idiographic
Reflexivity (social theory)
References[edit]
Jump up ^ Verstehen: The Sociology of Max Weber
Jump up ^ "Anti-positivism" Archived April 3, 2012, at the Wayback Machine. at Historylearningsite.co.uk
Jump up ^ "Verstehen": entry in the Online Dictionary of the Social Sciences
Jump up ^ Macionis, J., and Gerber, L. (2010). Sociology, 7th edition
Jump up ^ Macionis, J., and Gerber, L. (2010). Sociology, 7th edition
Jump up ^ Macionis, J., and Gerber, L. (2010). Sociology, 7th edition
Jump up ^ J. Gustav Droyen, Historik: Vorlesungen über Enzyklopädie und Methodologie der Geschichte. Stuttgart: Fromann-Holzboog, [1858] 1977: 22, 150f.
Jump up ^ J. Gustav Droyen, Grundriss der Historik, Berlin 1862, p. 4 ff.
Jump up ^ J. Gustav Droysen, Grundriss der Historik, Verlag von Veit & Comp., 1868, p. 11: §14.
Jump up ^ Lars Udehn, Methodological Individualism: Background, History and Meaning, Routledge, 2001, p. 27.
Jump up ^ W. Dilthey, Ideen über eine beschreibende und zergliedernde Psychologie, Berlin 1894, p. 1314.
Jump up ^ W. Dilthey, Introduction to the Human Sciences. Princeton: Princeton University Press, 1991.
Jump up ^ Hans-Georg Gadamer, Truth and method, Crossroad, 1989.
Jump up ^ Martin Heidegger, Ontology: The Hermeneutics of Facticity, Indiana University Press, 1999.
Jump up ^ Charles R. Bambach, Heidegger, Dilthey, and the crisis of historicism, Cornell University Press, 1995, p. 199–200.
Jump up ^ Georg Simmel, Die probleme der Gechichtsphilosophie. Eine erkentnistheoretische Studie. Munich: Verlag von Dunker und Humboldt, 1920.
Jump up ^ Macionis, Gerber, John, Linda (2011). Sociology. Toronto, ON: Pearson Canada Inc. pp. 32–33. ISBN 978-0-13-700161-3.
Jump up ^ Gerber, John J. Macionis, Linda M. Sociology (7th Canadian ed.). Toronto: Pearson Canada. ISBN 978-0-13-700161-3.
Jump up ^ Gingrich, Paul. "Max Weber". Sociology 250. University of Regina, Department of Sociology and Social Studies. Retrieved 21 February 2012.
Jump up ^ Macionis, Gerber, John, Linda (2011). Sociology. Toronto, ON: Pearson Canada Inc. p. 33. ISBN 978-0-13-700161-3.
External links[edit]
The dictionary definition of verstehen at Wiktionary
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3D modeling
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This article is about computer modeling within an artistic medium. For scientific usage, see Computer simulation.
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Three-dimensional (3D)
computer graphics
Fundamentals
Modeling
Scanning
Rendering
Printing
Software
Primary uses
3D models
Computer-aided design
Graphic design
Video games
Visual effects
Visualization
Virtual engineering
Virtual reality
Virtual cinematography
Related topics
Computer-generated imagery (CGI)
Animation
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3D display
Wireframe model
Texture mapping
Motion capture
Crowd simulation
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In 3D computer graphics, 3D modeling (or three-dimensional modeling) is the process of developing a mathematical representation of any surface of an object (either inanimate or living) in three dimensions via specialized software. The product is called a 3D model. Someone who works with 3D models may be referred to as a 3D artist. It can be displayed as a two-dimensional image through a process called 3D rendering or used in a computer simulation of physical phenomena. The model can also be physically created using 3D printing devices.
Models may be created automatically or manually. The manual modeling process of preparing geometric data for 3D computer graphics is similar to plastic arts such as sculpting.
3D modeling software is a class of 3D computer graphics software used to produce 3D models. Individual programs of this class are called modeling applications or modelers.
Contents
[hide]
1 Models
1.1 Representation
2 Modeling process
2.1 Human models
2.2 3D Clothing
3 Compared to 2D methods
4 3D model market
5 3D printing
6 Uses
7 Testing a 3D Solid Model
8 See also
9 References
Models[edit]
Three-dimensional model of a spectrograph[1]
Three-dimensional (3D) models represent a physical body using a collection of points in 3D space, connected by various geometric entities such as triangles, lines, curved surfaces, etc. Being a collection of data (points and other information), 3D models can be created by hand, algorithmically (procedural modeling), or scanned. Their surfaces may be further defined with texture mapping.
3D models are widely used anywhere in 3D graphics and CAD. Their use predates the widespread use of 3D graphics on personal computers. Many computer games used pre-rendered images of 3D models as sprites before computers could render them in real-time. The designer can then see the model in various directions and views, this can help the designer see if the object is created as intended to compared to their original vision. Seeing the design this way can help the designer/company figure out changes or improvements needed to the product.[2]
Today, 3D models are used in a wide variety of fields. The medical industry uses detailed models of organs; these may be created with multiple 2-D image slices from an MRI or CT scan. The movie industry uses them as characters and objects for animated and real-life motion pictures. The video game industry uses them as assets for computer and video games. The science sector uses them as highly detailed models of chemical compounds.[3] The architecture industry uses them to demonstrate proposed buildings and landscapes in lieu of traditional, physical architectural models. The engineering community uses them as designs of new devices, vehicles and structures as well as a host of other uses. In recent decades the earth science community has started to construct 3D geological models as a standard practice. 3D models can also be the basis for physical devices that are built with 3D printers or CNC machines.
Representation[edit]
A modern render of the iconic Utah teapot model developed by Martin Newell (1975). The Utah teapot is one of the most common models used in 3D graphics education.
Almost all 3D models can be divided into two categories.
Solid – These models define the volume of the object they represent (like a rock). Solid models are mostly used for engineering and medical simulations, and are usually built with constructive solid geometry
Shell/boundary – these models represent the surface, e.g. the boundary of the object, not its volume (like an infinitesimally thin eggshell). Almost all visual models used in games and film are shell models.
Solid and shell modeling can create functionally identical objects. Differences between them are mostly variations in the way they are created and edited and conventions of use in various fields and differences in types of approximations between the model and reality.
Shell models must be manifold (having no holes or cracks in the shell) to be meaningful as a real object. Polygonal meshes (and to a lesser extent subdivision surfaces) are by far the most common representation. Level sets are a useful representation for deforming surfaces which undergo many topological changes such as fluids.
The process of transforming representations of objects, such as the middle point coordinate of a sphere and a point on its circumference into a polygon representation of a sphere, is called tessellation. This step is used in polygon-based rendering, where objects are broken down from abstract representations ("primitives") such as spheres, cones etc., to so-called meshes, which are nets of interconnected triangles. Meshes of triangles (instead of e.g. squares) are popular as they have proven to be easy to rasterise (the surface described by each triangle is planar, so the projection is always convex); .[4] Polygon representations are not used in all rendering techniques, and in these cases the tessellation step is not included in the transition from abstract representation to rendered scene.
Modeling process[edit]
3D polygonal modelling of a human face.
There are three popular ways to represent a model:
Polygonal modeling – Points in 3D space, called vertices, are connected by line segments to form a polygon mesh. The vast majority of 3D models today are built as textured polygonal models, because they are flexible and because computers can render them so quickly. However, polygons are planar and can only approximate curved surfaces using many polygons.
Curve modeling – Surfaces are defined by curves, which are influenced by weighted control points. The curve follows (but does not necessarily interpolate) the points. Increasing the weight for a point will pull the curve closer to that point. Curve types include nonuniform rational B-spline (NURBS), splines, patches, and geometric primitives
Digital sculpting – Still a fairly new method of modeling, 3D sculpting has become very popular in the few years it has been around.[citation needed] There are currently three types of digital sculpting: Displacement, which is the most widely used among applications at this moment, uses a dense model (often generated by subdivision surfaces of a polygon control mesh) and stores new locations for the vertex positions through use of an image map that stores the adjusted locations. Volumetric, loosely based on voxels, has similar capabilities as displacement but does not suffer from polygon stretching when there are not enough polygons in a region to achieve a deformation. Dynamic tessellation is similar to voxel but divides the surface using triangulation to maintain a smooth surface and allow finer details. These methods allow for very artistic exploration as the model will have a new topology created over it once the models form and possibly details have been sculpted. The new mesh will usually have the original high resolution mesh information transferred into displacement data or normal map data if for a game engine.
A 3D fantasy fish composed of organic surfaces generated using LAI4D.
The modeling stage consists of shaping individual objects that are later used in the scene. There are a number of modeling techniques, including:
Constructive solid geometry
Implicit surfaces
Subdivision surfaces
Modeling can be performed by means of a dedicated program (e.g., Cinema 4D, Maya, 3ds Max, Blender, LightWave, Modo) or an application component (Shaper, Lofter in 3ds Max) or some scene description language (as in POV-Ray). In some cases, there is no strict distinction between these phases; in such cases modeling is just part of the scene creation process (this is the case, for example, with Caligari trueSpace and Realsoft 3D).
Complex materials such as blowing sand, clouds, and liquid sprays are modeled with particle systems, and are a mass of 3D coordinates which have either points, polygons, texture splats, or sprites assigned to them.
Human models[edit]
Main article: Virtual actor
The first widely available commercial application of human virtual models appeared in 1998 on the Lands' End web site. The human virtual models were created by the company My Virtual Mode Inc. and enabled users to create a model of themselves and try on 3D clothing.[5] There are several modern programs that allow for the creation of virtual human models (Poser being one example).
3D Clothing[edit]
Dynamic 3D Clothing Model made in Marvelous Designer
The development of cloth simulation software such as Marvelous Designer, CLO3D and Optitex, has enabled artists and fashion designers to model dynamic 3D clothing on the computer.[6] Dynamic 3D clothing is used for virtual fashion catalogs, as well as for dressing 3D characters for video games, 3D animation movies, for digital doubles in movies[7] as well as for making clothes for avatars in virtual worlds such as SecondLife.
Compared to 2D methods[edit]
A fully textured and lit rendering of a 3D model.
3D photorealistic effects are often achieved without wireframe modeling and are sometimes indistinguishable in the final form. Some graphic art software includes filters that can be applied to 2D vector graphics or 2D raster graphics on transparent layers.
Advantages of wireframe 3D modeling over exclusively 2D methods include:
Flexibility, ability to change angles or animate images with quicker rendering of the changes;
Ease of rendering, automatic calculation and rendering photorealistic effects rather than mentally visualizing or estimating;
Accurate photorealism, less chance of human error in misplacing, overdoing, or forgetting to include a visual effect.
Disadvantages compare to 2D photorealistic rendering may include a software learning curve and difficulty achieving certain photorealistic effects. Some photorealistic effects may be achieved with special rendering filters included in the 3D modeling software. For the best of both worlds, some artists use a combination of 3D modeling followed by editing the 2D computer-rendered images from the 3D model.
3D model market[edit]
A large market for 3D models (as well as 3D-related content, such as textures, scripts, etc.) still exists – either for individual models or large collections. Several online marketplaces for 3D content allow individual artists to sell content that they have created, including TurboSquid, CGStudio, CreativeMarket and CGTrader. Often, the artists' goal is to get additional value out of assets they have previously created for projects. By doing so, artists can earn more money out of their old content, and companies can save money by buying pre-made models instead of paying an employee to create one from scratch. These marketplaces typically split the sale between themselves and the artist that created the asset, artists get 40% to 95% of the sales according to the marketplace. In most cases, the artist retains ownership of the 3d model; the customer only buys the right to use and present the model. Some artists sell their products directly in its own stores offering their products at a lower price by not using intermediaries.
Over the last several years numerous marketplaces specialized in 3D printing models have emerged. Some of the 3D printing marketplaces are combination of models sharing sites, with or without a built in e-com capability. Some of those platforms also offer 3D printing services on demand, software for model rendering and dynamic viewing of items, etc. 3D printing file sharing platforms include Shapeways, Pinshape, Thingiverse, TurboSquid, CGTrader, Threeding, MyMiniFactory, and GrabCAD.
3D printing[edit]
Main articles: 3D printing and Rapid prototyping
3D printing is a form of additive manufacturing technology where a three dimensional object is created by laying down or build from successive layers of material.
3D printing is a great way to create objects because you can create objects that you couldn't make otherwise without having complex expensive molds created or by having the objects made with multiple parts. A 3D printed part can be edited by simply editing the 3D model. That avoids having to do any additional tooling which can save time and money. 3D printing is great for testing out an idea without having to go through the production process which is great for getting a physical form of the person/company's idea[8]
In recent years, there has been an upsurge in the number of companies offering personalized 3D printed models of objects that have been scanned, designed in CAD software, and then printed to the customer's requirements. As previously mentioned, 3D models can be purchased from online marketplaces and printed by individuals or companies using commercially available 3D printers, enabling the home-production of objects such as spare parts,[9] mathematical models,[10] and even medical equipment.[11]
Uses[edit]
Steps of forensic facial reconstruction of a mummy made in Blender by the Brazilian 3D designer Cícero Moraes.
3D modeling is used in various industries like films, animation and gaming, interior designing and architecture. They are also used in the medical industry for the interactive representations of anatomy. A wide number of 3D software are also used in constructing digital representation of mechanical models or parts before they are actually manufactured. CAD/CAM related software are used in such fields, and with these software, not only can you construct the parts, but also assemble them, and observe their functionality.
3D modelling is also used in the field of Industrial Design, wherein products are 3D modeled before representing them to the clients. In Media and Event industries, 3D modelling is used in Stage/Set Design.
The OWL 2 translation of the vocabulary of X3D can be used to provide semantic descriptions for 3D models, which is suitable for indexing and retrieval of 3D models by features such as geometry, dimensions, material, texture, diffuse reflection, transmission spectra, transparency, reflectivity, opalescence, glazes, varnishes, and enamels (as opposed to unstructured textual descriptions or 2.5D virtual museums and exhibitions using Google Street View on Google Arts & Culture, for example).[12] The RDF representation of 3D models can be used in reasoning, which enables intelligent 3D applications which, for example, can automatically compare two 3D models by volume.[13]
Testing a 3D Solid Model[edit]
3D Solid models can be tested in different ways depending on what is needed by using simulation, mechanism design, and analysis. If a motor is designed and assembled correctly (this can be done differently depending on what 3D modeling program is being used), using the mechanism tool the user should be able to tell if the motor or machine is assembled correctly by how it operates. Different design will need to be tested in different ways. For example; a pool pump would need a simulation ran of the water running through the pump to see how the water flows through the pump. These test verify if a product id developed correctly or if it needs to me modified to meet its requirements.
See also[edit]
This article is in a list format that may be better presented using prose. You can help by converting this article to prose, if appropriate. Editing help is available. (November 2016)
3CT
List of 3D modeling software
List of common 3D test models
3D computer graphics software
3D printing
3D scanner
Additive Manufacturing File Format
Building information modeling
Cloth modeling
Computer facial animation
Digimation's Library example
Digital geometry
Edge loop
Evolver is a portal, 3D modeler and market place for 3D characters
Geological modeling
Industrial CT scanning
Marching cubes
Open CASCADE
Polygon mesh
Polygonal modeling
Scaling (geometry)
SIGGRAPH
Stanford Bunny
Triangle mesh
Utah teapot
Voxel
B-rep
References[edit]
Look up modeler in Wiktionary, the free dictionary.
Jump up ^ "ERIS Project Starts". ESO Announcement. Retrieved 14 June 2013.
Jump up ^ "What is Solid Modeling? 3D CAD Software. Applications of Solid Modeling". Brighthub Engineering. Retrieved 2017-11-18.
Jump up ^ "3D Scanning Advancements in Medical Science". Konica Minolta. Retrieved 24 October 2011.
Jump up ^ Jon Radoff, Anatomy of an MMORPG Archived 2009-12-13 at the Wayback Machine., August 22, 2008
Jump up ^ "Lands' End First With New 'My Virtual Model' Technology: Takes Guesswork Out of Web Shopping for Clothes That Fit". PRNewswire. Lands' End. February 12, 2004. Retrieved 2013-11-24.
Jump up ^ "All About Virtual Fashion and the Creation of 3D Clothing". CGElves. Retrieved 25 December 2015.
Jump up ^ "3D Clothes made for The Hobbit using Marvelous Designer". 3DArtist. Retrieved 9 May 2013.
Jump up ^ "What is 3D Printing? The definitive guide". 3D Hubs. Retrieved 2017-11-18.
Jump up ^ "3D Printing Toys". Business Insider. Retrieved 25 January 2015.
Jump up ^ "Printout3D—Wolfram Language Documentation". reference.wolfram.com. Retrieved 2016-08-06.
Jump up ^ "New Trends in 3D Printing – Customized Medical Devices". Envisiontec. Retrieved 25 January 2015.
Jump up ^ Sikos, L. F. (2016). Rich Semantics for Interactive 3D Models of Cultural Artifacts. Communications in Computer and Information Science. 672. Springer International Publishing. pp. 169–180. doi:10.1007/978-3-319-49157-8_14.
Jump up ^ Yu, D.; Hunter, J. (2014). "X3D Fragment Identifiers—Extending the Open Annotation Model to Support Semantic Annotation of 3D Cultural Heritage Objects over the Web". International Journal of Heritage in the Digital Era. 3 (3): 579–596. doi:10.1260/2047-4970.3.3.579.
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Tongue map
From Wikipedia, the free encyclopedia
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The myth of the tongue map; that 1 tastes bitter, 2 tastes sour, 3 tastes salt, and 4 tastes sweet. Although this is a myth.
The tongue map or taste map or tongue taste or map map is a common misconception that different sections of the tongue are exclusively responsible for different basic tastes. It is illustrated with a schematic map of the tongue, with certain parts of the tongue labeled for each taste. Although widely taught in schools, this was scientifically disproven by later research; all taste sensations come from all regions of the tongue, although different parts are more sensitive to certain tastes.[1][2]
History[edit]
The theory behind this map originated from a paper written by Harvard psychologist D.P Hanig, which was a translation of a German paper, Zur Psychophysik des Geschmackssinnes, which was written in 1901.[3] The unclear representation of data in the former paper suggested that each part of the tongue tastes exactly one basic taste.[4][5]
The paper showed minute differences in threshold detection levels across the tongue,[6] but these differences were later taken out of context and the minute difference in threshold sensitivity was misconstrued in textbooks as a difference in sensitivity.[7]
While some parts of the tongue may be able to detect a taste before the others do, all parts are equally capable of conveying the qualia of all tastes. Threshold sensitivity may differ across the tongue, but intensity of sensation doesn't.[7]
The same paper included a taste bud distribution diagram that showed a "taste belt", similar to a "waste belt" but for your tongue.[8]
In 1974, Virginia Collings investigated the topic again, and confirmed that all the tastes exist on all parts of the tongue.[9]
Taste belt[edit]
The misinterpreted 1901 diagram in the article that sparked this myth shows human taste buds distributed in a "taste belt" along the outside of the tongue.
Prior to this, A. Hoffmann had concluded, in 1875, that the dorsal center of the human tongue has practically no fungiform papillae and taste buds,[10] and it was this finding that the diagram describes.
References[edit]
Jump up ^ O'Connor, Anahad (November 10, 2008). "The Claim: The tongue is mapped into four areas of taste". The New York Times. Retrieved June 24, 2011.
Jump up ^ Huang, Angela; Chen, Xiaoke; Hoon, Mark; Chandrashekar, Jayaram; Guo, Wei; Tränkner, Dimitri; Ryba, Nicholas; Zuker, Charles (August 24, 2006). "The cells and logic for mammalian sour taste detection". Nature. 442 (7105): 934–938. PMC 1571047  . PMID 16929298. doi:10.1038/nature05084. Retrieved June 24, 2011.
Jump up ^ Hänig, David (1901). "Zur Psychophysik des Geschmackssinnes". Philosophische Studien. 17: 576–623. Retrieved July 9, 2014.
Jump up ^ Wanjek, Christopher (August 29, 2006). "The Tongue Map: Tasteless Myth Debunked". Livescience.com. Retrieved June 24, 2011.
Jump up ^ David V. Smith; Robert F. Margolskee (March 2001). "The Taste Map: All Wrong". Scientific American.
Jump up ^ Jacob M. Andersen (Jan 2015). "Mythbusting The Tongue Map". ASDA.
^ Jump up to: a b The Chemotopic Organization of Taste wwwalt.med-rz.uni-sb.de Archived July 18, 2011, at the Wayback Machine.
Jump up ^ Chemotopic representation of the human tongue according to Hänig (1901) wwwalt.med-rz.uni-sb.de Archived July 18, 2011, at the Wayback Machine.
Jump up ^ Collings, V. B. (1974). "Human Taste Response as a Function of Locus of Stimulation on the Tongue and Soft Palate". Perception & Psychophysics. 16: 169–174. doi:10.3758/bf03203270.
Jump up ^ Hoffmann, A. (1875). "Über die Verbreitung der Geschmacksknospen beim Menschen" [On the spread of taste buds in humans]. Archiv für pathologische Anatomie und Physiologie und für klinische Medicin (in German). 62: 516–530. doi:10.1007/bf01928657.
[hide]
v
t
e
Taste
Basic tastes
Bitterness
Saltiness
Sourness
Sweetness
Umami
Anatomy
Epiglottis
Pharynx
Soft palate
Tongue
Gustology
Ageusia
Dysgeusia
Hypogeusia
Other
Aftertaste
Acquired taste
Pungency
Scoville scale
Supertaster
Tongue map
See also
Sight
Hearing
Smell
Touch
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