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more documentation, create a default luminaire if the scene description contains none

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Wenzel Jakob 2010-08-11 03:32:46 +02:00
parent 713d98ad85
commit 6c429ac43f
5 changed files with 133 additions and 1 deletions
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2
doc/Makefile
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@ -1,2 +1,2 @@
main.pdf: main.tex introduction.tex compiling.tex basics.tex integrator.tex acknowledgements.tex
main.pdf: main.tex introduction.tex compiling.tex basics.tex format.tex integrator.tex acknowledgements.tex
pdflatex main.tex

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doc/format.tex
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\section{Scene file format}
Mitsuba uses a very simple and general XML-based format to represent scenes.
The framework's underlying approach is to represents discrete blocks of functionality as plugins,
hence a scene file can essentially be interpreted as description that determines which
plugins should be instantiated and how they should be interface with each other.
In the following, we'll look at a few examples to get a feeling for the scope of the
format.
An simple scene might looks like this
\begin{xml}
<?xml version="1.0" encoding="utf-8"?>
<scene>
<shape type="obj">
<string name="filename" value="dragon.obj"/>
</shape>
</scene>
\end{xml}
This example already contains the most important things to know about format: you can have
\emph{objects} (such as the objects instantiated by the \code{scene} or \code{shape} tags), which are allowed to be nested within
each other. Each object optionally accepts \emph{properties} (such as \code{string}),
which further characterize its behavior. All objects except for the root object (the \code{scene})
cause the renderer to load and instantiate a plugin, hence you must provide the plugin name using
\code{type=".."} parameter.
The tags let the renderer know what kind of object is to be instantiated: for instance \code{obj} is a
WaveFront OBJ loader, which conforms to the \emph{Shape} interface. Similarly,
you could write
\begin{xml}
<?xml version="1.0" encoding="utf-8"?>
<scene>
<shape type="sphere">
<float name="radius" value="10"/>
</shape>
</scene>
\end{xml}
This loads a different plugin (\code{sphere}) which is still a \emph{Shape}, but instead represents
a sphere configured with a radius of 10 world-space units. Mitsuba ships with
a large number of plugins; please refer to the next chapter for a reference.
The most common scene setup is to declare an integrator, some geometry, a camera, a film, a sampler
and one or more luminaires. Here is a more complex example:
\begin{xml}
<?xml version="1.0" encoding="utf-8"?>
<scene>
<integrator type="path"> <!-- Path trace an 8-bounce GI solution -->
<integer name="maxDepth" value="8"/>
</integrator>
<!-- Instantiate a perspective camera with 45 degrees field of view -->
<camera type="perspective">
<!-- Rotate the camera around the Y axis by 180 degrees -->
<transform name="toWorld">
<rotate y="1" angle="180"/>
</transform>
<float name="fov" value="45"/>
<!-- Render with 32 samples per pixel using a basic
independent sampling strategy -->
<sampler type="independent">
<integer name="sampleCount" value="32"/>
</sampler>
<!-- Generate an EXR image at HD resolution -->
<film type="exrfilm">
<integer name="width" value="1920"/>
<integer name="height" value="1080"/>
</film>
</camera>
<!-- Add a dragon mesh made of rough glass (stored as OBJ) -->
<shape type="obj">
<string name="filename" value="dragon.obj"/>
<bsdf type="roughglass">
<!-- Tweak the roughness parameter of the material -->
<float name="alphaB" value="0.01"/>
</bsdf>
</shape>
<!-- Add a mesh stored using a more compact representation -->
<shape type="serialized">
<string name="filename" value="lightsource.serialized"/>
<transform name="toWorld">
<translate x="5" x="-3" z="1"/>
</transform>
<!-- This mesh is an area luminaire -->
<luminaire type="area">
<rgb name="intensity" value="100,400,100"/>
</luminaire>
</shape>
</scene>
\end{xml}
This example introduces several new object types (\code{integrator, camera, sampler, film, bsdf}, and \code{luminaire})
and a few property types (\code{integer}, \code{transform}, and \code{rgb}).
Objects are usually declared at the top level except if there is some
inherent relation that links them to another object. For example, BSDFs are usually specific to a certain geometric object, so
they appear as a child object of a shape. Similarly, the sampler and film both affect the way in which
rays are generated from the camera, hence they are nested inside it.
Note that you should always put properties before nested child objects, otherwise you'll see something like the following slightly cryptic
XML validation error. For instance,
\begin{xml}
...
<shape type="obj">
<bsdf type="phong"/>
<string name="filename" value="lucy.obj"/>
</shape>
...
\end{xml}
produces
\begin{shell}
Caught a critical exeption: 2010-08-11 03:23:31 ERROR main [src/mitsuba/shandler.cpp:359] Error in file "/home/wenzel/mitsuba/test.xml" (line 63): Element 'string' is not valid $\texttt{for}$ content model: '(((integer|float|point|vector|boolean|transform|string|spectrum|rgb)|blackbody),((bsdf|subsurface|ref)|luminaire))'
\end{shell}
\subsection{Property types}
\subsubsection{Numbers}
\subsubsection{Spectra}
\subsubsection{Transformations}
\subsubsection{Vectors, Positions}
\subsubsection{Strings}
\subsection{Instancing materials}
\subsection{Including external files}

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doc/main.tex
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@ -110,6 +110,7 @@
\include{compiling}
\include{basics}
\include{format}
\include{plugins}
\include{integrator}
\include{parallelization}
\include{acknowledgements}

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doc/plugins.tex Normal file
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\section{Plugin reference}
TBD

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src/librender/scene.cpp
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@ -183,6 +183,8 @@ void Scene::configure() {
m_integrator->configure();
}
if (m_camera == NULL) {
Log(EWarn, "No camera found -- adding a default camera");
Properties props("perspective");
/* Create a perspective camera with 45deg. FOV, which can see the whole scene */
AABB aabb;
@ -200,6 +202,11 @@ void Scene::configure() {
m_camera->configure();
m_sampler = m_camera->getSamplerX();
}
if (m_luminaires.size() == 0) {
Log(EWarn, "No luminaires found -- adding a constant environment source");
addChild("", PluginManager::getInstance()->createObject(Luminaire::m_theClass, Properties("constant")));
}
if (m_media.size() > 1)
Log(EError, "Scenes are currently restricted to at most one participating medium.");