/// <param name="position">The position.</param>
/// <param name="ignoredLights">A set of lights to ignore, if any. If this value is a HashSet of LightSources it will be used directly, otherwise the sequence is copied.</param>
/// <returns>The created receiver</returns>
public LightReceiver AddLightReceiver (Vector2 position, LightIgnorePredicate lightIgnorePredicate = null) {
var result = new LightReceiver {
Position = position,
LightIgnorePredicate = lightIgnorePredicate
};
LightReceivers.Add(result);
return result;
}
/// <param name="position">The position.</param>
/// <param name="ignoredLights">A set of lights to ignore, if any. If this value is a HashSet of LightSources it will be used directly, otherwise the sequence is copied.</param>
/// <returns>The created receiver</returns>
public LightReceiver AddLightReceiver(Vector2 position, LightIgnorePredicate lightIgnorePredicate = null)
{
var result = new LightReceiver {
Position = position,
LightIgnorePredicate = lightIgnorePredicate
};
LightReceivers.Add(result);
return(result);
}
/// <summary>
/// Computes the amount of light received at a given position in the environment.
/// </summary>
/// <param name="position">The position.</param>
/// <param name="lightIgnorePredicate">A predicate that returns true if a light source should be ignored.</param>
/// <returns>The total amount of light received at the location (note that the result is not premultiplied, much like LightSource.Color)</returns>
public bool ComputeReceivedLightAtPosition(Vector2 position, out Vector4 result, LightIgnorePredicate lightIgnorePredicate = null)
{
result = Vector4.Zero;
// FIXME: This enumerates all lights in the scene, which might be more trouble than it's worth.
// Using the itemboundsenumerator ended up being too expensive due to setup cost.
foreach (var light in Environment.LightSources)
{
var opacity = light.Opacity;
if (opacity <= 0f)
{
continue;
}
float rampStart = light.RampStart, rampEnd = light.RampEnd;
var lightPosition = light.Position;
var deltaFromLight = (position - lightPosition);
var distanceFromLightSquared = deltaFromLight.LengthSquared();
if (distanceFromLightSquared > (rampEnd * rampEnd))
{
continue;
}
if ((lightIgnorePredicate != null) && lightIgnorePredicate(light))
{
continue;
}
ArraySegment <DeltaLine> lines;
if (!_ObstructionsByLight.TryGetValue(light, out lines))
{
return(false);
}
IntersectionTestsLastFrame += lines.Count;
if (FindObstruction(position, lightPosition, lines))
{
continue;
}
var distanceFromLight = (float)Math.Sqrt(distanceFromLightSquared);
var distanceScale = 1f - MathHelper.Clamp((distanceFromLight - rampStart) / (rampEnd - rampStart), 0f, 1f);
if (light.RampMode == LightSourceRampMode.Exponential)
{
distanceScale *= distanceScale;
}
// FIXME: Feed distance through ramp texture somehow
var lightColorScaled = light.Color;
// Premultiply by alpha here so that things add up correctly. We'll have to reverse this at the end.
lightColorScaled *= (distanceScale * opacity);
result += lightColorScaled;
}
// Reverse the premultiplication, because we want to match LightSource.Color.
if (result.W > 0)
{
var unpremultiplyFactor = 1.0f / result.W;
result.X *= unpremultiplyFactor;
result.Y *= unpremultiplyFactor;
result.Z *= unpremultiplyFactor;
}
return(true);
}
