commit fa9e2298a7a29db30cacb0654973d5d6c2d3aba1
parent 85c1b4b7537fa133a10b6f646f5ac2bb6b1e5b31
Author: Vincent Forest <vincent.forest@meso-star.com>
Date: Tue, 6 Jul 2021 16:31:16 +0200
Improve the htrdr-combustion man page
Add a reference to the htrdr-image man page. Notify the units used by
the command. Briefly explain the "Super Man" rendering algorithm when a
combustion chamber is defined. Add an example that computes a flux map.
Diffstat:
1 file changed, 67 insertions(+), 26 deletions(-)
diff --git a/doc/htrdr-combustion.1.txt.in b/doc/htrdr-combustion.1.txt.in
@@ -34,13 +34,14 @@ DESCRIPTION
The purpose of *htrdr-combustion* is to perform radiative transfer computations
in a scene representing a combustion semi-transparent medium enlightened by a
laser sheet. The combustion medium may be surrounded by solid boundaries (inner
-limits of the combustion chamber). The program will currently compute the
-monochromatic image (in the visible, at a given frequency) of the combustion
-medium: collected light comes from the laser, and is scattered by soot
-aggregates within the flame before eventually reaching the camera.
+limits of the combustion chamber). The program will currently compute, in the
+visible at a given frequency, the monochromatic image or the radiative flux
+density of the combustion medium: collected light comes from the laser, and is
+scattered by soot aggregates within the flame before eventually reaching the
+sensor.
Data about the gaseous medium have to be provided on the vertices of a
-unstructured tetrahedron mesh: pressure, temperature and concentrations of H2O,
+unstructured tetrahedral mesh: pressure, temperature and concentrations of H2O,
CO2 and CO have to be provided for every spatial position used to define this
mesh. These data have to be provided in anticipation of future developments for
the longwave range: since the gas is assumed to be transparent in the visible,
@@ -57,16 +58,23 @@ absorption and scattering cross-sections of soot aggregates, as well as their
scattering function.
The Monte-Carlo algorithm that accounts for the visible intensity is inspired
-from the algorithm used for solar radiation in the *htrdr-atmosphere* command.
-It was adapted to partially illuminated scenes in order to solve convergence
-issues. The algorithm is presented in the following article:
+from the algorithm used for solar radiation in the *htrdr-atmosphere*(1)
+command. It was adapted to partially illuminated scenes in order to solve
+convergence issues. The algorithm is presented in the following article:
"Null-collision meshless Monte-Carlo - a new reverse Monte-Carlo algorithm
designed for laser-source emission in absorbing/scattering inhomogeneous
media". M. Sans et al, JQSRT, 2021 [2].
+In *htrdr-combustion* the spatial unit 1.0 corresponds to one meter while the
+estimated monochromatic radiances and flux densities are saved in W/sr/m^2 and
+W/m^2 respectively. Computed images are stored in the *htrdr-image*(5) file
+format.
+
*htrdr-combustion* implements a mixed parallelism: on one computer (i.e. a
node) it uses a shared memory parallelism, and it relies on the message passing
-interface [4] to parallelize the computations between several nodes.
+interface [4] to parallelize the computations between several nodes. We can
+thus launch * htrdr-combustion * either directly, or via a process launcher
+like *mpirun*(1) to distribute the rendering over several nodes.
OPTIONS
-------
@@ -97,14 +105,15 @@ OPTIONS
*-d* <__laser__|__octree__>::
When define with the _laser_ argument, write in _output_ the geometry of the
laser sheet saved in the VTK file format [3]. With the _octree_ argument,
- write in _output_ the space partitioning data structure used to speed up the
- radiative transfer computations in the combustion medium. The octree is saved
- following the VTK file format [3]. Each node stores the minimum and the
- maximum of the extinction coefficients of the tetrahedra that the node
+ write in _output_ a VTK file that stores the octree leaves of the space
+ partitioning data structure used to speed up the radiative transfer
+ computations in the combustion medium. Each leaf stores the minimum and the
+ maximum of the extinction coefficients of the tetrahedra that the leaf
overlaps.
*-F* <__fractal-coefficients__:...>::
- Fractal parameters of the RDG-FA model. Available fractal coefficients are:
+ Fractal parameters of the RDG-FA model. This option disable the *-I* option
+ if it was previously set. Available fractal coefficients are:
**dimension**=_real_;;
Fractal dimension. By default it is set to
@@ -118,8 +127,15 @@ OPTIONS
Force overwrite of the _output_ file.
*-g* <__geometry-parameter__:...>::
- Define the geometry of the combustion chamber. Available geometry parameters
- are:
+ Define the geometry of the combustion chamber. Note that this geometry do not
+ prevent the camera from viewing the medium or the laser from illuminating it,
+ even if they are outside the combustion chamber. The rendering algorithm
+ ensures that they are not occluded by this geometry like with a two-way
+ mirror. When the laser is out of geometry, its emissive surface is seen as if
+ it were following the interior surface of the chamber. Likewise, the radiance
+ seen by the camera outside the chamber is the radiance that reaches it as if
+ its image plane were following the surface of the geometry. Available
+ geometry parameters are:
**mats**=__materials__;;
Path to the *htrdr-materials*(5) that defines the media and materials used
@@ -129,11 +145,11 @@ OPTIONS
Path to the *htrdr-obj*(5) file that represents the mesh of the combustion
chamber. Following the *htrdr-obj*(5) fileformat, the interface of the
submitted mesh must be defined as a thin interface, i.e. it must be
- composed of 3 components separated by the ':' character. By
- convention, *htrdr-combustion* expects the outside environment to be called
- "air" and the medium inside the combustion chamber to be called "chamber".
- No assumption is made on the name of the surface material excepted that it
- has to reference a valid material.
+ composed of 3 components separated by the ':' character. By convention,
+ *htrdr-combustion* expects the outside environment to be called "air" and
+ the medium inside the combustion chamber to be called "chamber". No
+ assumption is made on the name of the surface material excepted that it has
+ to reference a valid material.
*-h*::
List short help and exit.
@@ -202,8 +218,9 @@ OPTIONS
combustion medium.
*-R* <__rectangle-parameter__:...>::
- Switch in flux map computation. The rectangular sensor onto which
- the flux is integrated is defined by the following parameters:
+ Compute a radiatve flux density map rather than an image. The rectangular
+ sensor onto which the flux is integrated is defined by the following
+ parameters:
**pos**=**_x_**,**_y_**,**_z_**;;
Position of the center of the rectangle. By default it is set to
@@ -265,7 +282,7 @@ EXAMPLES
Make htrdr-combustion verbose (option *-v*) and render an image of a combustion
medium whose tetrahedral mesh is stored in *tetra.sth* and its associated
-thermodynamic properties are saved in *thermprops.atrtp*. The spectrally
+thermodynamic properties are saved in *thermprops.atrtp*. The spectrallyole
varying indices of the medium are listed in the *refract_ids.atrri* file. The
center of the laser surface emission is positioned at the origin and its
direction is aligned to the Y axis. The definition of the rendered image is
@@ -290,7 +307,8 @@ volumetric acceleration structure in *octree.cache* or reused it if it was
already populated in a previous run with compatible input data. Set the finest
resolution of this acceleration structure to 1000 along the major extend of the
medium and use a optical thickness criterion of 5 to build it. Use the *-f*
-option to force the overwrite of the *output* file if it exists.
+option to force the overwrite of the *output* file if it exists and use *-s* to
+speed up the rendering with the available SIMD instruction sets.
$ htrdr-combustion -v \
-m tetra.sth \
@@ -304,7 +322,27 @@ option to force the overwrite of the *output* file if it exists.
-O octree.cache \
-V 1000 \
-T 5 \
- -o output -f
+ -o output -f -s
+
+Compute a flux density map whose definition is *500* by *500* pixels. The flux
+density per pixel is estimated with *64* realisations; the flux density for the
+entire sensor is thus calculated with 16 million realisations (`500 * 500
+* 64`). The sensor on which the flux density is calculated is a square with
+sides measuring *0.05* meter. Its center is positioned at the origin and points
+to the Z axis.
+
+ $ htrdr-combustion -v \
+ -m tetra.sth \
+ -p thermprops.atrtp \
+ -r refract_ids.atrri \
+ -l pos=0,0,0:tgt=0,1,0:up=0,0,1:sz=0.001,0.2 \
+ -w 500 \
+ -R pos=0,0,0:tgt=0,0,1:up=0,1,0:sz=0.05,0.05 \
+ -i def=500x500:spp=64 \
+ -O octree.cache \
+ -V 1000 \
+ -T 5 \
+ -o map.txt -f -s
Write into *octree.vtk* a representation of the volumetric acceleration
structure.
@@ -335,7 +373,9 @@ Sans et al, JQSRT, 2021 - <https://doi.org/10.1016/j.jqsrt.2021.107725>
COPYRIGHT
---------
Copyright © 2018, 2019, 2020, 2021 |Meso|Star> <contact@meso-star.com>.
+
Copyright © 2018, 2019, 2021 CNRS.
+
Copyright © 2018, 2019 Université Paul Sabatier
<contact-edstar@laplace.univ-tlse.fr>.
@@ -351,6 +391,7 @@ SEE ALSO
*atrtp*(5),
*atrri*(5),
*htrdr-atmosphere*(1),
+*htrdr-image*(5),
*htrdr-obj*(5),
*htrdr-materials*(5),
*mpirun*(1),
