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Added sun intensity modulation as a function of altitude.

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nissim.hadar 2017-12-29 23:47:42 -08:00
parent 7260b4ff7b
commit b6bbf1abe1
1 changed files with 24 additions and 7 deletions
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31
scripts/developer/sunModel.js
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@ -8,7 +8,7 @@
// Distributed under the Apache License, Version 2.0.
// See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//
// Code is based on the NOAA model - see https://www.esrl.noaa.gov/gmd/grad/solcalc/
// Sun angle is based on the NOAA model - see https://www.esrl.noaa.gov/gmd/grad/solcalc/
//
(function() {
// Utility functions for trig. calculations
@ -213,10 +213,10 @@
Math.cos(latitude) * Math.cos(theta_rads) * Math.cos(hourAngleRadians);
csz = Math.min(1.0, Math.max(-1.0, csz));
var zenith = toDegrees(Math.acos(csz));
var azDenom = ( Math.cos(latitude) * Math.sin(toRadians(zenith)));
var zenith_degs = toDegrees(Math.acos(csz));
var azDenom = ( Math.cos(latitude) * Math.sin(toRadians(zenith_degs)));
if (Math.abs(azDenom) > 0.001) {
azRad = (( Math.sin(latitude) * Math.cos(toRadians(zenith)) ) - Math.sin(theta_rads)) / azDenom;
azRad = (( Math.sin(latitude) * Math.cos(toRadians(zenith_degs)) ) - Math.sin(theta_rads)) / azDenom;
if (Math.abs(azRad) > 1.0) {
if (azRad < 0.0) {
azRad = -1.0;
@ -240,7 +240,7 @@
}
// Atmospheric Refraction correction
var exoatmElevation = 90.0 - zenith;
var exoatmElevation = 90.0 - zenith_degs;
if (exoatmElevation > 85.0) {
var refractionCorrection = 0.0;
} else {
@ -257,7 +257,7 @@
refractionCorrection = refractionCorrection / 3600.0;
}
var solarZenith = zenith - refractionCorrection;
var solarZenith = zenith_degs - refractionCorrection;
var solarAltitude_degs = 90.0 - solarZenith; // aka solar elevation
// Convert to XYZ
@ -268,7 +268,24 @@
var zPos = Math.cos(solarAltitude) * Math.cos(solarAzimuth);
var yPos = -Math.sin(solarAltitude);
Entities.editEntity(entityID, { keyLight : {direction: { x: xPos, y: yPos, z: zPos }}});
// Compute intensity, modelling the atmosphere as a spherical shell
// The optical air mass ratio at zenith is 1.0, and around 38.0 at the horizon
// The ratio is limited between 1 and 38
var EARTH_RADIUS_KM = 6371.0;
var ATMOSPHERE_THICKNESS_KM = 9.0;
var r = EARTH_RADIUS_KM / ATMOSPHERE_THICKNESS_KM;
var opticalAirMassRatio = Math.sqrt(r * r * csz * csz + 2 * r + 1) - r * csz;
opticalAirMassRatio = Math.min(38.0, Math.max(1.0, opticalAirMassRatio));
Entities.editEntity(
entityID, {
keyLight : {
direction: { x: xPos, y: yPos, z: zPos },
intensity: 1.0 / opticalAirMassRatio
}
}
);
},
COMPUTATION_CYCLE