private void UpdateSky()
{
// Update ephemeris model.
#if XBOX
_ephemeris.Time = new DateTimeOffset(_time.Ticks, TimeSpan.Zero);
#else
_ephemeris.Time = _time;
#endif
_ephemeris.Update();
// Update rotation of milky way. We also need to add an offset because the
// cube map texture is rotated.
_milkyWayNode.PoseWorld = new Pose(
(Matrix33F)_ephemeris.EquatorialToWorld.Minor
* Matrix33F.CreateRotationZ(ConstantsF.PiOver2 + -0.004f)
* Matrix33F.CreateRotationX(ConstantsF.PiOver2 + -0.002f));
// Update rotation of stars.
_starfieldNode.PoseWorld = new Pose((Matrix33F)_ephemeris.EquatorialToWorld.Minor);
// Update direction of sun.
SunDirection = (Vector3F)_ephemeris.SunDirectionRefracted;
var sunUp = SunDirection.Orthonormal1;
_sunNode.LookAt(SunDirection, sunUp);
// Update direction of moon.
var moonDirection = (Vector3F)_ephemeris.MoonPosition.Normalized;
var moonUp = (Vector3F)_ephemeris.EquatorialToWorld.TransformDirection(Vector3D.Up);
_moonNode.LookAt(moonDirection, moonUp);
// The moon needs to know the sun position and brightness to compute the moon phase.
_moonNode.SunDirection = (Vector3F)_ephemeris.SunPosition.Normalized;
_moonNode.SunLight = Ephemeris.ExtraterrestrialSunlight * SunlightScale;
// The ScatteringSky needs the sun direction and brightness to compute the sky colors.
_scatteringSkyNode.SunDirection = SunDirection;
_scatteringSkyNode.SunColor = Ephemeris.ExtraterrestrialSunlight * ScatteringSkyLightScale;
// Update the light directions.
_sunlightNode.LookAt(-SunDirection, sunUp);
_moonlightNode.LookAt(-moonDirection, moonUp);
// The ScatteringSkyNode can compute the actual sunlight.
SunLight = _scatteringSkyNode.GetSunlight();
// Undo the ScatteringSkyLightScale and apply a custom scale for the sunlight.
SunLight = SunLight / ScatteringSkyLightScale * SunlightScale;
// The ScatteringSkyNode can also compute the ambient light by sampling the
// sky hemisphere.
AmbientLight = _scatteringSkyNode.GetAmbientLight(256);
AmbientLight = AmbientLight / ScatteringSkyLightScale * SunlightScale;
// Desaturate the ambient light to avoid very blue shadows.
AmbientLight = InterpolationHelper.Lerp(
new Vector3F(Vector3F.Dot(AmbientLight, GraphicsHelper.LuminanceWeights)),
AmbientLight,
0.5f);
// The Ephemeris model can compute the actual moonlight.
Vector3F moonlight, moonAmbient;
Ephemeris.GetMoonlight(
_scatteringSkyNode.ObserverAltitude,
2.2f,
_ephemeris.MoonPosition,
(float)_ephemeris.MoonPhaseAngle,
out moonlight,
out moonAmbient);
moonlight *= MoonlightScale;
moonAmbient *= MoonlightScale;
// Scale sun light to 0 at horizon.
var directionalLightColor = SunLight;
directionalLightColor *= MathHelper.Clamp(SunDirection.Y / 0.1f, 0, 1);
var directionalLight = ((DirectionalLight)_sunlightNode.Light);
directionalLight.Color = directionalLightColor;
((DirectionalLight)_moonlightNode.Light).Color = moonlight;
((AmbientLight)_ambientLightNode.Light).Color = AmbientLight + moonAmbient + LightPollution;
// Use the sunlight color to create a bright sun disk.
var sunDiskColor = SunLight;
sunDiskColor.TryNormalize();
_sunNode.GlowColor0 = sunDiskColor * Ephemeris.ExtraterrestrialSunlight.Length * SunlightScale * 10;
if (_enableClouds)
{
// Update lighting info of cloud layer nodes.
_cloudLayerNode0.SunDirection = SunDirection;
_cloudLayerNode0.SunLight = SunLight;
_cloudLayerNode0.AmbientLight = AmbientLight;
// The second cloud layer uses simple unlit clouds (only ambient lighting).
_cloudLayerNode1.SunDirection = SunDirection;
_cloudLayerNode1.SunLight = Vector3F.Zero;
_cloudLayerNode1.AmbientLight = AmbientLight + SunLight;
// Use the cloud map as the texture for the directional light to create cloud shadows.
if (EnableCloudShadows)
{
directionalLight.Texture = _cloudLayerNode0.CloudMap.Texture;
}
else
{
directionalLight.Texture = null;
}
// Compute a texture offset so that the current sun position and the projected cloud
// shadows match.
// Since sky dome is always centered on the camera, position the sunlight node in
// line with the camera.
var cameraPosition = _cameraObject.CameraNode.PoseWorld.Position;
var upVector = Vector3F.AreNumericallyEqual(SunDirection, Vector3F.UnitZ) ? Vector3F.UnitY : Vector3F.UnitZ;
_sunlightNode.LookAt(cameraPosition + SunDirection, cameraPosition, upVector);
// Choose a scale for the cloud shadows.
directionalLight.TextureScale = new Vector2F(-1000);
// Get the scaled texture offset for the sun direction.
directionalLight.TextureOffset = _cloudLayerNode0.GetTextureCoordinates(SunDirection) *
directionalLight.TextureScale;
}
// The ScatteringSkyNode can also estimate a fog color by sampling the horizon colors.
Vector3F fogColor = _scatteringSkyNode.GetFogColor(256, FogSampleAngle);
// Desaturate the fog color.
fogColor = InterpolationHelper.Lerp(
new Vector3F(Vector3F.Dot(fogColor, GraphicsHelper.LuminanceWeights)),
fogColor,
FogSaturation);
// Find any FogNode in the scene and update its fog color.
foreach (var fogNode in ((Scene)_scene).GetSubtree().OfType <FogNode>())
{
var fog = fogNode.Fog;
fog.Color0 = fog.Color1 = new Vector4F(fogColor, 1);
fog.ScatteringSymmetry = FogScatteringSymmetry;
}
// TODO: If the fog is dense, reduce the direct light and increase the ambient light.
}
