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Topic: Phong reflection model

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Phong lighting

Raytracing

Bui tuong phong

Radiosity

Flat shading

Procedural surface

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	Phong materials - Valve Developer Community
		The Phong reflection model is basically a simplified method of deciding the shade of a specific point on a 3D surface.
		Phong observed that for very shiny surfaces the specular highlight was small and that the intensity fell off rapidly, while for duller surfaces it was larger and fell off more gradually.
		Phong exponent, mask and Fresnel terms are combined to give a specular term which is combined with the diffuse solution in the final output.
	developer.valvesoftware.com /wiki/Phong (1888 words)

	Phong shading - Wikipedia, the free encyclopedia
		The term Phong shading is used indiscriminately to describe both an illumination model and an interpolation method in 3D computer graphics.
		Phong reflection is a local illumination model devised by Bui Tuong Phong and can produce a certain degree of realism in three-dimensional objects by combining three elements - diffuse, specular and ambient for each considered point on a surface.
		Phong observed that for very shiny surfaces the specular highlight was small and the intensity fell off rapidly, while for duller surfaces it was larger and fell off more slowly.
	en.wikipedia.org /wiki/Phong_shading (555 words)

	Phong reflection model - Wikipedia, the free encyclopedia
		The Phong reflection model is a shading model (see also Phong shading), used heavily in 3D computer graphics for assigning shades to each individual pixel that is rasterized of some abstract representation of an object such as a sphere or cone.
		It was developed by Bui Tuong Phong in his University of Utah Ph.D. Thesis paper "Illumination for Computer Generated Pictures" in 1973.
		The Phong reflection model is a simplification of the more general rendering equation, which takes advantage of the following simplifications when deciding the shade of a pixel during rasterization of a surface:
	en.wikipedia.org /wiki/Phong_reflection_model (462 words)

	Phong Light Model Equation - (Site not responding. Last check: 2007-10-18)
		Specular reflection is when the reflection is stronger in one viewing direction, i.e., there is a bright spot, called a specular highlight.
		Shading 15 4.1 The Phong Reflection model 17 4.2 The...
		Phong illumination shader implements an illumination model based on both diffuse reflection and specular reflection of a surface.
	equation.fabca.com /index.php?k=phong-light-model-equation (959 words)

	Project 38 : text report
		Phong gives more accurate highlights and is usually the preferred model whereas Gouraud tends to be confined to applications where the diffuse component is sufficient, or to preview images before a final render.
		In this reflection model the intensity is a function of the surface normal which produces local variations on a smooth surface.
		The Law of Reflection states that the angle of incidence =the angle of reflection and the incidence and reflected rays and the surface normal are coplanar.
	www.scism.sbu.ac.uk /inmandw/past/9697/projects/rep38/prj38.html (10314 words)

	GameDev.net - Fast Phong Shading by Gary Bishop
		Phong shading is a well known algorithm for producing a realistic shading but it has not been used by real-time systems because of the 3 additions, 1 division and 1 square root required per pixel for its evaluation.
		PHONG SHADING: Phong shading, [Phong, 1973], eliminates "flattening out" and dull surfaces and reduces Mach bands but has not, to my knowledge, been used in any real-time system because of the large amount of computation required for its usual formulation.
		Phong's method determines the intensity of each point using an approximate surface normal that is linearly interpolated from the true surface normals specified at the vertices, N(x,y) = Ax + By + C where A, B and C are chosen to interpolate the normal across the polygon.
	www.gamedev.net /reference/articles/article326.asp (1306 words)

	The RenderMan Academy - Phong Shading Model
		Since light is reflected equally in all directions the perceived illumination of the surface is not dependent on the position of the observer.
		Specular Reflection - Light is reflected mainly in the direction of the reflected ray and is attenuated by an amount dependent upon the physical properties of the surface.
		Since the light reflected from the surface is mainly in the direction of the reflected ray the position of the observer determines the perceived illumination of the surface.
	www.rendermanacademy.com /docs/phong_model.htm (1646 words)

	The Online POV-Ray Tutorial: Finish Reference
		Reflection requires an extra ray to be traced to determine the reflected color, while with transparent objects, an extra ray must be traced to determine the color that is being filtered.
		Reflection tends to like quite nice with a some phong or specular thrown in.
		Roughness is to specular as phong_size is to phong.
	library.thinkquest.org /3285/language/finish.html (2193 words)

	Reflection Models (Site not responding. Last check: 2007-10-18)
		Reflection models (or BRDFs, which stands for Bidirectional Reflectance Distribution Function) are at the heart of computer graphics.
		Short of this, a model of reflectance can be constructed from the first principles, based on physics of light-surface interaction.
		An attempt was made to preserve Phong parameters (since most graphics people are quite familiar with what it means to have, say, n=100 Phong model) and make this model as simple and efficient as possible to allow a hardware implementation some day.
	www.cs.utah.edu /~michael/brdfs (383 words)

	Indian Webdesigner (Site not responding. Last check: 2007-10-18)
		The Phong reflection model is a shading model, used heavily in 3D computer graphics for assigning shades to each individual pixel that is rasterized of some abstract representation of an object such as a sphere or cone.
		If we first define, for each light source in the scene to be rendered, the components $i_s, i_d and i_{al} where these are the intensities (often as RGB values) of the specular, diffuse and ambient components of the light sources respectively.$
		$k_a : ambient$ reflection constant, the ratio of reflection of the ambient term present in all points in the scene rendered
	www.indianwebdesigner.com /index.php?title=Phong_reflection_model (433 words)

	Fast Phong Shading (Site not responding. Last check: 2007-10-18)
		Phong shading is a well known algorithm for producing a realistic shading but it has not been used by real-time systems because of the 3 additions, 1 division and 1 square root required per pixel for its evaluation.
		The shading algorithms must determine the intensity of each point within a triangle from the surface normals, and a vector to the light source, L. The light source is assumed to be at infinity so that L is independent of the point on which the light shines.
		Figure 4 is a comparision of Phong shading with the eye at infinity and with the eye at a true perspective distance.
	gamma.cs.unc.edu /~gb/siggraph86.html (1698 words)

	Waterloo/CGL/Image Synthesis/Reflection Models (Site not responding. Last check: 2007-10-18)
		Reflectance can be described using a bidirectional reflectance distribution function, which in general will depend on at least four degrees of freedom: the incident and view directions at a surface.
		Reflection models computed by such simulation can be quite complex even if the reflection model and the geometric model of the microgeometry are simple.
		The reflectance function for grass used above was obtained by shooting photons at microgeometry consisting of blades oriented randomly, and estimating the distribution of scattered photons.
	www.cgl.uwaterloo.ca /Projects/rendering/refl.html (577 words)

	Phong Shading and Gouraud Shading
		The Phong model describes the interaction of light with a surface, in terms of the properties of the surface and the nature of the incident light.
		Light reflected from a glossy surfac e tends to leave the surface along vector R, where R is such that incident angle is equal to reflection angle.
		The area over which specular reflection is seen is commonly referred to as a highlight and this is an important aspect of Phong Shading: the color of the specularly reflected light is different from that of the diffuse reflected light.
	www.nbb.cornell.edu /neurobio/land/OldStudentProjects/cs490-95to96/guo/report.html (2528 words)

	CTM0709E: Graphics and Animation Programming - Week 5
		In a Global Illumination Model the reflection of light from a surface is modelled as in the local model with the addition of light incident on the surface after multiple reflections between other surfaces.
		The phong Illumination model describes the effects of ambient light as well as diffuse and specular reflection of light illuminates a surface.
		Reflection model, illumination model and bi-directional reflectivity function are additional concept that we cover.
	mercury.tvu.ac.uk /gpa/gpa_12.html (1393 words)

	Phong reflections for normal facing away from light - GameDev.Net Discussion Forums
		R is the reflection vector and using the standard method of calculating the reflection vector this does not go to zero when the normal is facing away from the light.
		It seems like this wrapping of phong highlights around the back side of a surface relative to the light source is inherent to Phong reflection and it also seems that it gives unwanted results and that offline renderers get rid of the effect using some kind of clamping.
		Having realised that Phong reflection can give positive values for normals facing away from the light though that aliasing makes sense - any time you do a hard clamp in a shader you're going to get aliasing if the values either side of the clamp are significantly different.
	www.gamedev.net /community/forums/topic.asp?topic_id=445990 (2006 words)

	Delphi3D - Rapid OpenGL Development
		Phong's model is one of the most common lighting models in computer graphics.
		Phong's model is a local illumination model, which means only direct reflections are taken into account.
		Phong's lighting model is ubiquitous in modern-day computer graphics, so it's important to understand it.
	www.delphi3d.net /articles/viewarticle.php?article=phong.htm (1812 words)

	Manual/Glossary - BlenderWiki
		Modeling is the process of manipulating and combining simple primitive shapes into representations of real or imaginary "things" - animals, people, machinery, vegetation, scenery, etc. Models may be assembled and arranged in Blender's 3D viewport as scenes, or may be exported under a number of common file formats for use in other 3D programs.
		Phong shading term is used indiscriminately to describe both an illumination model and an interpolation method in 3D computer graphics.
		Phong reflection is a local illumination model and can produce a certain degree of realism in three-dimensional objects by combining three elements - diffuse, specular and ambient for each considered point on a surface.
	wiki.blender.org /index.php/Manual/Glossary (5385 words)

	CPE 471 Introduction to Computer Graphics (Site not responding. Last check: 2007-10-18)
		Tristimulus model: = each scalar component value (r,g,b) is the result of the integration of a "= ;sensitivity function" with the full wavelength intensity function (or spectrum).
		Specular — reflecte= d light is highly directional and depends upon the angle of incidence from a point source light, angle of reflection, and angle to the view direction (eye position=).
		Reflected light is MAXIMUM when angle to eye =3D angle of reflection.
	www.csc.calpoly.edu /~hitchner/CSC471/lectureNotes/Lecture11.mht (3001 words)

	[No title]
		In order for this information to be relevant or meaningful, the models must be positioned and displayed in such a way that they align with their corresponding real objects.
		The diffuse reflection of the surface by direct illumination of a curve light is then evaluated by approximating the curve light with a series of linear segments.
		The specular reflection component due to a curve light source is represented by an integration taking Phong's specular model as the kernel and evaluated by summing the contributions from the linear segments.
	www.eg.org /EG/DL/BibDB/cgf14.bib (4581 words)

	Untitled Document
		This is a shading model that is currently widely used in rendering 3D graphics.
		To compensate from the light lost by neglecting these reflections, a term is added to represent ambient lighting.
		Starting at the light source, a ray of light is traced to a surface, where it will be either absorbed, reflected, or refracted.
	projects.olin.edu /ahs/HOT2004/Computers/graphics.htm (538 words)

	Reflectance Model
		After the diffuse reflection formula is applied, the scaled light is then applied to the diffuse reflectance formula to determine the diffuse component at that vertex.
		Modeling specular reflection requires that the system not only know the direction that light is traveling, but also the direction to the viewer's eye.
		As with the diffuse reflectance formula, this formula produces values that range from -1.0 to 1.0, which are clamped to the range of 0.0 to 1.0 and used to scale the light reflecting from the vertex.
	msdn.microsoft.com /archive/en-us/dx8_vb/directx_vb/graphics_understand_7e43.asp?frame=true (978 words)

	shader: "phong"
		A reflectance model conforming with the popular Phong model in which reflections are greatest in the `mirror' direction of a surface opposite the viewing direction with respect to the surface normal.
		Reflectance coefficients are provided which allow specification of the amount of ambient, diffuse and specular light reflected, corresponding to arguments
		The reflection is made sharper with large values of the exponent, such as 10.0.
	download.graphisoft.com /ftp/techsupport/documentation/developer_docs/BasicLibraryDoc/LightWorksIntegration/LW_Programmers_ref/phong.html (115 words)

	Radiosity
		The amount of light reflected is independent of the direction that the surface is being viewed from since surfaces that reflect diffusely reflect in all directions equally.
		The intensity of a specular reflection is also proportional to the cosine of the angle between the view direction and the direction the light is reflected in.
		To model this, Phong uses a constant ambient illumination term that when multiplied by the ambient reflectivity of the surface, gives the ambient component of illumination.
	web.cs.wpi.edu /~matt/courses/cs563/talks/radiosity.html (1220 words)

	[No title]
		The geometric part in the imaging process with a pinhole camera is modelled by a transformation from 3D to 2D, which we call the perspective projection.
		Now we scan-convert the triangles in the model one by one, but for each pixel, before writing it to the frame buffer, we test if its depth is smaller than the one already in the Z-buffer.
		The brightness of a Lambertian surface is proportional to the cosine of the angle between the surface normal and a vector directed at the light source.
	www.cs.huji.ac.il /~danix/modeling/lecture3.html (1237 words)

	460a8_s02
		When the program first starts, a default view of the projected image of a polygon mesh model of the Bezier patch (using the 4-parameter viewing setup discussed in class) should appear in the client area of the program's window.
		If the user selects "Flat Shaded", you are to use the Phong illumination/reflection model (discussed in class) to display a flat shaded image of the Bezier patch.
		Then using the Phong model with diffuse reflection only and a single color for the patch,(e.g., green, so that kg=1, kr=kb=0), it should calculate the intensity of light reflected from each polygon in the patch.
	www.cs.binghamton.edu /~reckert/460/460a8_s02.html (1037 words)

	460a8_s04 (Site not responding. Last check: 2007-10-18)
		Then using the Phong illumination/reflection model, with diffuse reflection only, the program should calculate the R, G, B intensities of the light reflected from each visible polygon in the scene.
		This will not be the case if the viewing parameters change since we are only considering diffuse reflection, and, in the Phong model, that is independent of the position of the viewer.
		In other words, assign to each object a specular reflection coefficient, ks, and a specular exponent (n), and include the specular term from the Phong equation.
	www.cs.binghamton.edu /~reckert/460/460a8_s04.html (682 words)

	Simple Illumination Model
		The Fresnel equation states that for a perfectly reflecting surface the angle of incidence equals the angle of reflection.
		Artists sometimes use flat shading to look at the polygons of a solid model they are creating.
		Gouraud shading (Henri Gouraud, 1971) is used to achieve smooth lighting on low-polygon surfaces using the Lambertian diffuse lighting model.
	csis.pace.edu /~marchese/CG/Lect10New/cg_l10new.htm (974 words)

	Flatland Visualization for Qualitative Analysis of Image Synthesis Techniques
		Local reflection is a image synthesis technique that is fast enough to occur in real time and generally creates images of acceptable quality.
		Diffuse reflection, also known as Lambertian reflection, is the result of when light hits a surface and the reflected rays are scattered uniformly in all directions.
		Phong shading, which is the standard method for local illumination, differs from Gouraud shading in that instead of performing the color calculation at vertices and interpolating between them we perform normal interpolation between vertices and perform color calculation for each sample.
	www.gvu.gatech.edu /~jarek/courses/6491/L10/Ingram (1901 words)

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