The
main program of Virtual
Retina needs an xml file
that defines with precision all the parameters for the retinal
scheme chosen for the simulation. This xml file is customizable:
each biological feature, as defined by the five points mentionned
above, corresponds to its own xml node, which can be present or not in
the xml definition file. One example is shown below.
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<!--
Hello, this is a sample retina description
file, implementing an array ofspiking X-type ganglion cells with
contrast gain control, without microsaccades. This file is one of the
custom files you can directly use to define
your retina!!
Use it with sequences normalized between 0 and 255. If you want to use
the retina for a sequence coded between 0 and M, input-luminosity-range
must be set at M. All spatial filtering scales are expressed in
'angular degrees'. Correspondance
with pixels is made through parameter pixels-per-degree.
-->
<retina-description-file>
<retina
temporal-step__sec ="0.005"
input-luminosity-range="255"
pixels-per-degree="10.0">
<log-polar-scheme
fovea-radius__deg="50"
scaling-factor-outside-fovea__inv-deg="0.02"/>
<outer-plexiform-layer>
<linear-version
center-sigma__deg="0.10"
surround-sigma__deg="0.30"
center-tau__sec="0.01"
surround-tau__sec="0.01"
opl-amplification="5"
opl-relative-weight="1"
leaky-heat-equation="1" />
</outer-plexiform-layer>
<contrast-gain-control
opl-amplification="250"
bipolar-to-adaptation-threshold="0.5"
adaptation-sigma__deg="0.5"
adaptation-tau__sec="0.03"
adaptation-feedback-amplification="500"
bipolar-inert-leaks="10"/>
<parvocellular-ganglion-layer
transient-tau__sec="0.03"
transient-relative-weight="0.75"
bipolar-linear-threshold="0"
value-at-linear-threshold="300"
bipolar-amplification="100">
<spiking-channel>
<circular-spiking-channel
diameter="300" fovea-density="1" g-leak="50"
noise-V="0.0" noise-refr__sec="0"
tau-refr__sec="0.003" random-init="1"/>
</spiking-channel>
</parvocellular-ganglion-layer>
</retina>
</retina-description-file>
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Simpler description files can also be used. Following example
implements a very simple retinal scheme, with only a linear filtering
stage, and no spike generation.
<!--
Hello, this is a sample retina description file, implementing a simple
Center/Surround linear filter, as produced by the Outer Plexiform Layer
of a retina. No log-polar scheme, no contrast gain control, and no
spiking layer.
This file is one of the custom files
you can directly use to define your retina.
-->
<retina-description-file>
<retina
temporal-step__sec ="0.005"
input-luminosity-range="255"
pixels-per-degree="10.0">
<outer-plexiform-layer>
<linear-version
center-sigma__deg="0.10"
surround-sigma__deg="0.30"
center-tau__sec="0.01"
surround-tau__sec="0.01"
opl-amplification="5"
opl-relative-weight="1"
leaky-heat-equation="1" />
</outer-plexiform-layer>
</retina>
</retina-description-file>
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Virtual Retina
description files are totally customizable. Following this link, you will find a
commented XML file that showed all possible elements of the retina
program.
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