fgdata/Environment/clouds-altitude-interpolate.xml

<?xml version="1.0" ?>
<!--
 This file is part of FlightGear, the free flight simulator
 http://www.flightgear.org/

 Copyright (C) 2009 Torsten Dreyer, Torsten (at) t3r _dot_ de

 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License as
 published by the Free Software Foundation; either version 2 of the
 License, or (at your option) any later version.

 This program is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 General Public License for more details.
-->
<PropertyList>
  <params>
    <from>environment/metar/clouds/layer[0]/elevation-ft</from>
    <to>/environment/clouds/layer[0]/elevation-ft</to>
  </params>
  <name>MetarController:clouds:altitude_interpolate</name>
  <type>exponential</type>
  <filter-time>
    <condition>
      <!-- dont't interpolate to -9999 or if more than 2000ft offset -->
      <or>
        <less-than>
          <property alias="../../../../../params/from"/>
          <value>-9000</value>
        </less-than>
        <less-than>
          <property alias="../../../../../params/to"/>
          <value>-9000</value>
        </less-than>
        <greater-than>
          <expression>
            <abs>
              <difference>
                <property alias="../../../../../../../../params/from"/>
                <property alias="../../../../../../../../params/to"/>
              </difference>
            </abs>
          </expression>
          <value>2000</value>
        </greater-than>
      </or>
    </condition>
    <value>0</value>
  </filter-time>
  
  <filter-time>60</filter-time>
  
  <enable>
    <condition>
      <property>/environment/metar/valid</property>
      <property>/environment/params/metar-updates-environment</property>
    </condition>
  </enable>
  <input alias="../params/from"/>
  <output alias="../params/to"/>
</PropertyList>