79 lines
4.4 KiB
TeX
79 lines
4.4 KiB
TeX
\part{Using Mitsuba}
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\textbf{Disclaimer:} This is manual documents the usage, file format, and
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internal design of the Mitsuba rendering system. It is currently a work
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in progress, hence some parts may still be incomplete or missing.
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\section{About Mitsuba}
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Mitsuba is a research-oriented rendering system in the style of PBRT
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(\url{www.pbrt.org}), from which it derives much inspiration.
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It is written in portable C++, implements unbiased as well
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as biased techniques, and contains heavy optimizations targeted
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towards current CPU architectures.
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Mitsuba is extremely modular: it consists of a small set of core libraries
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and over 100 different plugins that implement functionality ranging
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from materials and light sources to complete rendering algorithms.
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In comparison to other open source renderers, Mitsuba places a strong
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emphasis on experimental rendering techniques, such as path-based
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formulations of Metropolis Light Transport and volumetric
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modeling approaches. Thus, it may be of genuine interest to those who
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would like to experiment with such techniques that haven't yet found
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their way into mainstream renderers, and it also provides a solid
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foundation for research in this domain.
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Other design considerations are:
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\parheader{Performance:}
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Mitsuba provides optimized implementations of the most commonly
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used rendering algorithms. By virtue of running on a shared foundation, comparisons between them can
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better highlight the merits and limitations of different approaches. This is in contrast to, say,
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comparing two completely different rendering products, where technical information on the underlying
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implementation is often intentionally not provided.
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\parheader{Robustness:}
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In many cases, physically-based rendering packages force the user to model scenes with the underlying
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algorithm (specifically: its convergence behavior) in mind. For instance, glass windows are routinely
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replaced with light portals, photons must be manually guided to the relevant parts of a scene, and
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interactions with complex materials are taboo, since they cannot be importance sampled exactly.
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One focus of Mitsuba will be to develop path-space light transport algorithms, which handle such
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cases more gracefully.
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\parheader{Scalability:} Mitsuba instances can be merged into large clusters, which transparently distribute and
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jointly execute tasks assigned to them using only node-to-node communcation. It has successfully
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scaled to large-scale renderings that involved more than 1000 cores working on a single image.
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Most algorithms in Mitsuba are written using a generic parallelization layer, which can tap
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into this cluster-wide parallelism. The principle is that if any component of the renderer produces
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work that takes longer than a second or so, it at least ought to use all of the processing power
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it can get.
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The renderer also tries to be very conservative in its use of memory, which allows it to handle
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large scenes (>30 million triangles) and multi-gigabyte heterogeneous volumes on consumer hardware.
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\parheader{Realism and accuracy:} Mitsuba comes with a large repository of physically-based
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reflectance models for surfaces and participating media. These implementations
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are designed so that they can be used to build complex shader networks, while
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providing enough flexibility to be compatible with a wide range of different
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rendering techniques, including path tracing, photon mapping, hardware-accelerated rendering
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and bidirectional methods.
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The unbiased path tracers in Mitsuba are battle-proven and produce
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reference-quality results that can be used for predictive rendering, and to verify
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implementations of other rendering methods.
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\parheader{Usability:}
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Mitsuba comes with a graphical user interface to interactively explore scenes. Once a suitable
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viewpoint has been found, it is straightforward to perform renderings using any of the
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implemented rendering techniques, while tweaking their parameters to find the most suitable
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settings. Experimental integration into Blender 2.5 is also available.
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\section{License}
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Mitsuba is free software and can be redistributed and modified under the terms of the GNU General
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Public License (Version 3) as provided by the Free Software Foundation.
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\remarks{
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\item Being a ``viral'' license, the GPL automatically applies to all
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derivative work. Amongst other things, this means that without express
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permission, Mitsuba's source code is \emph{off-limits} to companies that
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develop rendering software not distributed under a compatible license.
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}
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