Metropolis light transport
Encyclopedia
The Metropolis light transport (MLT) is a SIGGRAPH
1997 paper by Eric Veach and Leonidas J. Guibas
, describing an application of a variant of the Monte Carlo method
called the Metropolis-Hastings algorithm
to the rendering equation
for generating images from detailed physical descriptions of three dimensional
scenes.
The procedure constructs paths from the eye to a light source using bidirectional path tracing, then constructs slight modifications to the path. Some careful statistical calculation (the Metropolis algorithm) is used to compute the appropriate distribution of brightness over the image. This procedure has the advantage, relative to bidirectional path tracing, that once a path has been found from light to eye, the algorithm can then explore nearby paths; thus difficult-to-find light paths can be explored more thoroughly with the same number of simulated photons. In short, the algorithm generates a path and stores the path's 'nodes' in a list. It can then modify the path by adding extra nodes and creating a new light path. While creating this new path, the algorithm decides how many new 'nodes' to add and whether or not these new nodes will actually create a new path.
Metropolis Light Transport is an unbiased method that, in some cases (but not always), converges to a solution of the rendering equation quicker than other unbiased algorithms, path tracing and bidirectional path tracing.
SIGGRAPH
SIGGRAPH is the name of the annual conference on computer graphics convened by the ACM SIGGRAPH organization. The first SIGGRAPH conference was in 1974. The conference is attended by tens of thousands of computer professionals...
1997 paper by Eric Veach and Leonidas J. Guibas
Leonidas J. Guibas
Leonidas John Guibas is a professor of computer science at Stanford University, where he heads the geometric computation group and is a member of the computer graphics and artificial intelligence laboratories. Guibas was a student of Donald Knuth at Stanford, where he received his Ph.D. in 1976...
, describing an application of a variant of the Monte Carlo method
Monte Carlo method
Monte Carlo methods are a class of computational algorithms that rely on repeated random sampling to compute their results. Monte Carlo methods are often used in computer simulations of physical and mathematical systems...
called the Metropolis-Hastings algorithm
Metropolis-Hastings algorithm
In mathematics and physics, the Metropolis–Hastings algorithm is a Markov chain Monte Carlo method for obtaining a sequence of random samples from a probability distribution for which direct sampling is difficult...
to the rendering equation
Rendering equation
In computer graphics, the rendering equation is an integral equation in which the equilibrium radiance leaving a point is given as the sum of emitted plus reflected radiance under a geometric optics approximation. It was simultaneously introduced into computer graphics by David Immel et al. and...
for generating images from detailed physical descriptions of three dimensional
3D computer graphics
3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...
scenes.
The procedure constructs paths from the eye to a light source using bidirectional path tracing, then constructs slight modifications to the path. Some careful statistical calculation (the Metropolis algorithm) is used to compute the appropriate distribution of brightness over the image. This procedure has the advantage, relative to bidirectional path tracing, that once a path has been found from light to eye, the algorithm can then explore nearby paths; thus difficult-to-find light paths can be explored more thoroughly with the same number of simulated photons. In short, the algorithm generates a path and stores the path's 'nodes' in a list. It can then modify the path by adding extra nodes and creating a new light path. While creating this new path, the algorithm decides how many new 'nodes' to add and whether or not these new nodes will actually create a new path.
Metropolis Light Transport is an unbiased method that, in some cases (but not always), converges to a solution of the rendering equation quicker than other unbiased algorithms, path tracing and bidirectional path tracing.
See also
- Indigo RendererIndigo RendererIndigo Renderer is a 3D rendering software that uses unbiased rendering technologies to create photo-realistic images. In doing so, Indigo uses equations that simulate the behaviour of light, with no approximations or guesses taken...
— A commercial unbiased 3D renderer that uses MLT - KerkytheaKerkytheaKerkythea is a standalone rendering system that supports raytracing and Metropolis light transport, uses physically accurate materials and lighting — and is distributed as freeware...
— Another unbiased free 3D renderer that uses MLT - Maxwell RenderMaxwell RenderMaxwell Render is a software package that aids in the production of photorealistic images from computer 3D model data; a 3D renderer. It was introduced as an early alpha on December 2004 and it utilized a global illumination algorithm based on a metropolis light transport variation.- Overview...
— A commercial unbiased renderer based on MLT - LuxRenderLuxRenderLuxRender is an open source software rendering system for physically correct image synthesis. The program runs on Microsoft Windows, Mac OS X and Linux and exporters are available for Blender, SketchUp, Cinema 4D, XSI, DAZ Studio, and Maya.-Overview:...
— An open source unbiased renderer that uses MLT