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Topic: Diffuse interreflection

	Diffuse reflection - Wikipedia, the free encyclopedia
		Diffuse reflection is the reflection of light from an uneven or granular surface such that an incident ray is seemingly reflected at a number of angles.
		Diffuse interreflection is a process whereby light reflected from an object strikes other objects in the surrounding area, illuminating them.
		Diffuse interreflection specifically describes light reflected from objects which are not shiny or specular.
	en.wikipedia.org /wiki/Diffuse_reflection (243 words)

	7.5.1 Introduction
		Radiosity is a lighting technique to simulate the diffuse exchange of radiation between the objects of a scene.
		diffuse: influences the amount of diffuse reflection of incoming light.
		This diffuse interreflection can be seen if you place a white chair in a room full of blue carpet, blue walls and blue curtains.
	www.mat.univie.ac.at /~kriegl/Skripten/CG/node160.html (449 words)

	Citations: A Ray Tracing Solution for Diffuse Interreflection - Ward, Rubinstein, Clear (ResearchIndex)
		, accurately computes the diffuse interreflections by shooting a large number of undirected rays into the scene, distributed over a hemisphere placed over the intersection point of the ray with the object.
		Diffuse illumination is computed separately and cached in an octree.
		As suggested by its name, the irradiance caching technique works by caching the diffuse indirect illumination component of global illumination [34] A global illumination lighting solution can be calculated as the sum of a direct illumination term and an indirect illumination term.
	citeseer.ist.psu.edu /context/88488/0 (1778 words)

	RADIANCE Indirect Calculation
		No matter how successful we are at removing the specular reflections and direct illumination from the integral (1), the cost of determining the remaining diffuse indirect contributions is too great to recalculate at every pixel because this requires tracing hundreds of rays to reduce the variance to tolerable levels.
		Therefore, most ray-tracing calculations ignore diffuse interreflection between surfaces, using a constant "ambient" term to replace the missing energy.
		The basic idea is to perform a full evaluation of Equation (1) for indirect diffuse contributions only as needed, caching and interpolating these values over each surface.
	radsite.lbl.gov /radiance/papers/sg94.1/indirect.html (1087 words)

	Vase - Blender Artists Forums
		Caustics are usually achieved by shooting photons at reflective/refractive objects and aim to produce highlights on diffuse surfaces around metallic or glass-like object.
		Radiosity is mostly used to compute diffuse interreflection in a scene, primarily to achieve color-bleeding.
		Diffuse "reflection" isnt really reflection at all, it is scattering.
	blenderartists.org /forum/showthread?t=32837 (807 words)

	POV-Ray 3.1 User Documentation Page 160.
		Radiosity is an extra calculation that more realistically computes the diffuse interreflection of light.
		Diffusely interreflected light is a function of the objects around the point in question.
		Since this is recursively defined to millions of levels of recursion, in any real life scene, every point is illuminated at least in part by every other part of the scene.
	bip.anatomy.upenn.edu /~rob/povhtml/pov161.html (2250 words)

	Realistic Indoor Daylight Illumination
		The combination of a large diffuse light source, the sky, and a strong direct light source, the sun, usually requires a very large amount of samples per ray to capture the environment.
		The main modification to LRT was to correctly sample the BSDF function of the surfaces, weighting each component (diffuse reflection, diffuse transmission, specular reflection, specular transmission) to correctly bounce or absorb a photon.
		However, combining path-traced sampling of the diffuse reflection with monte-carlo sampling of the direct environmental illumination proved excessively costly to render with low noise, and so we explored using a simple derivative of the PhotonMap integrator for far faster indirect illumination.
	graphics.stanford.edu /~katokop1/cs348b/final (1244 words)

	Comp 136 --- Fall '96 --- Lecture 29
		Given a scene composed entirely of opaque diffusely reflecting surfaces (some of which may be diffuse light emitters) the energy at a single point x in the scene is given by the Lambertian illumination model:
		The equation above may be expressed as "the intensity reflected at a point x is dependent on the diffuse reflectivity and the integral of all intensities (weighted by the projected area of the emitter) incident upon that point from objects in the scene".
		The scene is decomposed into a collection of elements (often called patches in the radiosity literature), the union of which is all surfaces in the scene, and the pairwise intersection of which is empty.
	www.cs.unc.edu /~mcmillan/comp136/Lecture29 (1037 words)

	eScience Lectures Notes : Global Illumination models : Radiosity
		If a surface is defined to be a "diffuse reflector" of light energy, any light energy which strikes the surface will be reflected in all directions, dependent only on the angle between the surface's normal and the incoming light vector.
		Another variation on the basic diffuse radiosity solution adds the contribution of light passing through a participating medium, such as smoke, fog, or water vapor in the air.
		As noted previously, the inherent diffuse nature of the basic radiosity algorithm has been relaxed with the development of multiple pass algorithms which incorporate both the diffuse and specular components of light.
	cs.anu.edu.au /escience/lecture/cg/GlobalIllumination/radiosity/printCG.en.html (2856 words)

	ACM SIGGRAPH CAMPFIRE: perceptually adaptive graphics
		The presence of shadows, specular reflections, caustics, and diffuse interreflection provide important cues to the human visual system and help determine relationships between objects.
		In this way, each group will be linked to a set of nearby groups for the purposes of local interreflection, and to an environment map and surrogate source list for the purposes of generating shadows and reflections.
		Local interreflection may be computed using any combination of object-space and image-space algorithms, since complexity is held in check by grouping and image segmentation.
	isg.cs.tcd.ie /campfire/gregward.html (1126 words)

	VIVID 2.0 format
		In "the real world" when light strikes diffuse surfaces such as walls, some of it is scattered back into the room.
		The diffuse color is the actual color of the object as seen when illuminated by a full white light.
		Since the diffuse color of the object is affected by the angle the light hits the surface this randomization can produce a sort of coarse texuture to an object.
	astronomy.swin.edu.au /~pbourke/dataformats/vivid (7573 words)

	Rayshade User's Guide and Reference Manual - 6 - Surfaces and Atmospheric Effects
		Use the given color to approximate those surface-surface interactions (e.g., diffuse interreflection) not modeled by the ray tracing process.
		The diffuse contribution from each non-shadowed light source at P» is equal to the diffuse color of the surface scaled by the cosine of the angle between N» and the vector from P» to the light source.
		If a light source illuminates a translucent surface from the side opposite that from which a ray approaches, illumination computations are performed, using the given color as the surface's diffuse color, and the given exponent as the Phong highlight exponent.
	www.fbe.unsw.edu.au /Learning/Rayshade/Guide/SURFACES.HTM (1359 words)

	3D Animation Workshop: Lesson 94: More Rendering Refinements - webreference.com
		We examined the interreflection of diffuse colors of surfaces in a scene, a process named Global Illumination in Mental Ray, and often called radiosity.
		These highlights are understood as reflections of direct light sources, and are contrasted in computer graphics with the indirect reflections of the colors of other objects in the scene (as on a chrome or mirror surface).
		To make up for the lack of interreflected lighting, all of the objects in the scene are slightly illuminated independently of any light sources.
	www.webreference.com /3d/lesson94 (673 words)

	Citations: A ray tracing solution for diffuse interreflection - Gregory, Ward, Rubinstein, Clear (ResearchIndex)
		To decide which method to use, variance should be analyzed, but the general rule is that specular surfaces should be dealt with using the implicit calculation and diffuse surfaces are treated explicitly.
		The indirect lighting in a diffuse environment produces smooth shading variation due to multiple and recursive interactions among objects, and is commonly solved by zonal methods with a discretized environment [25, 63, 29, 6, 72] or ray tracing with cached indirect lighting
		To prevent this recursion from continuing forever, rays are either followed a fixed number of bounces away from the eye or until the illumination contribution of a ray to the final image is deemed negligible.
	citeseer.ist.psu.edu /context/626135/0 (2718 words)

	Some interesting things said pre-Apollo 11 moon walk - Page 2 - Bad Astronomy and Universe Today Forum (Site not responding. Last check: 2007-11-03)
		The radiant heat transfer problem (which is identical to the diffuse interreflection problem) for a Boeing 701 satellite requires several days' computation on one of our most powerful computers.
		The level of illumination visible across the vertical dimension of Aldrin's body is fully consistent with being lit from the portions of the lunar surface that lie to either side of the LM's shadow, and to a lesser extent by Armstrong's space suit.
		When he says "about 70% of the reflected light is reflected diffusely," that's to say that 30% of the reflected light will behave in ways affected by other laws.
	www.bautforum.com /showthread.php?p=101496#post101496 (6953 words)

	Radiosity - Ray Tracing
		Among these effects are specular reflection and refraction, diffuse interreflection, spectral effects, and various others.
		They are mostly due to the interaction of light with the surfaces of various objects, and are in general very costly to simulate.
		This method is very good at simulating specular reflections and transparency, since the rays that are traced through the scenes can be easily bounced at mirrors and refracted by transparent objects.
	www.cg.tuwien.ac.at /research/rendering/rays-radio (730 words)

	Christiaan Paul Gribble (Site not responding. Last check: 2007-11-03)
		Specifically, the impact of ambient occlusion and physically based diffuse interreflection is investigated using a formal user study.
		However, using an experimental study, we demonstrate that effects from diffuse interreflection aid viewers' comprehension of three-dimensional structure and spatial relationships within these datasets.
		Using a simple matching task, we show that diffuse interreflection, or more accurate approximations to it, provide additional cues that enable viewers to better understand the details of particle geometry.
	www.sci.utah.edu /~cgribble/research (2599 words)

	Rendered Realities > Portfolio > renderBitch (Site not responding. Last check: 2007-11-03)
		i have not implemented multiple diffuse scattering within the volumetrics using the photon map yet, although that is a possible extension for the future.
		i set the diffuse inter-reflection settings to be identical in both programs.
		photon map (approximate solution) is used for for higher order diffuse inter-reflections (at least one diffuse bounce), or if we have had many specular bounces.
	www.renderedrealities.net /portfolio/renderbitch.html (3274 words)

	Photon Mapping - Zack Waters
		Radiosity is a finite element method that computes a view independent GI solution as a finite mesh.
		The environment is divided up into patches that are uniform and perfectly diffuse and energy is transferred amongst these patches until equalized.
		This tight coupling of the lighting information to the geometry is costly to calculate and meshing artifacts can occur if not carefully constructed.
	web.cs.wpi.edu /~emmanuel/courses/cs563/write_ups/zackw/photon_mapping/PhotonMapping.html (2321 words)

	od[forum] > Light objects
		Feb 18 2003, 11:07 AM Raytraced shadows might be too slow for most applications of the light array method for soft, diffused illumination BUT Houdini/Mantra is very fast at generating shadow maps.
		Even back in the 4.05/4.1 days I was able to create arrays of a hundred or more point lights and blow through the shadow map process in a matter of minutes on what would be ancient hardware by today's standards (450-500MHz PIII based SGI 320).
		Until H6 it's still a practical way of achieving realistic lighting for applications where diffuse interreflection or specular-to-diffuse reflection isn't an absolute must.
	www.odforce.net /forum/lofiversion/index.php/t634.html (695 words)

	The RADIANCE 3.1 Synthetic Imaging System (Site not responding. Last check: 2007-11-03)
		A diffuse reflection component may be given for the front side with rfdif, gfdif and bfdif for the front side of the surface or rbdif, gbdif and bbdif for the back side.
		The diffuse transmittance (must be the same for both sides by physical law) is given by rtdif, gtdif and btdif.
		The reflectance functions should be bidirectional, and under no circumstances should the sum of reflected diffuse, transmitted diffuse, reflected specular, transmitted specular and the integrated directional diffuse component be greater than one.
	astronomy.swin.edu.au /~pbourke/dataformats/rad/rad31.html (6371 words)

	Radiance Digest, v2n4
		I began with a cubic room covered with totally diffusive white plastic (reflectivity 2/3) and a single small light source inside.
		The diffude interreflection in this case should produce ambient light with total energy twice as large as the energy of the light source.
		It does not follow the usual "radiosity" finite element approach, but it does calculate diffusehis as part of an independent graphics study course.) I have a couple questions I was hoping yo 1) We have a large skylight in the roof of the lobby.
	caad.arch.ethz.ch /CAAD/ray/digests_html/v2n4.html (5140 words)

	More refutations through CG of Cosmic Dave's site - Bad Astronomy and Universe Today Forum
		Had a fill light been used on a stage to light the front of the astronaut, the shadow on the ground would have been lighter, too.
		You could duplicate it in the computer, but you would have to micromodel the texture of the surface and provide for diffuse interreflection to adjust to that texture.
		That's a radiosity solution, as I'm sure you recognize, and to do a diffuse interreflection render on a micromodeled texture would be more CPU time than anyone would care to expend.
	www.bautforum.com /showthread.php?p=17630#post17630 (3106 words)

	[No title]
		Then, in the main simulation, emitting patches are selected with probability proportional to their fraction, which is an approximation of (diffuse incident) importance, and directions for emission or reflection are chosen based on the statistics in the PxP array.
		Does not divide the scene into patches, but sends particles to pixels in the image plane.
		Section 4.5 describes the use of diffuse importance for importance-driven refinement of hierarchical radiosity." } @BOOK{Glassner95, author = "Andrew S. Glassner", title = "Principles of Digital Image Synthesis", publisher = "Morgan Kaufmann Publishers", year = 1995, keywords = {image synthesis, global illumination, adjoints, radiosity, radiance, importance}, comments = "Textbook on image synthesis including global illumination.
	www.seanet.com /~myandper/importance_graphics.bib (1092 words)

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