public SampleResult March(DistanceField field, double minimum, double maximum, Vec3 fog)
{
SampleResult result = field.Sample(CurrentPosition);
while (true)
{
if (result.Distance < minimum)
{
break;
}
if (DistanceTraveled > maximum)
{
DistanceTraveled = maximum;
break;
}
CurrentPosition = CurrentPosition + Direction * result.Distance;
DistanceTraveled += result.Distance;
result = field.Sample(CurrentPosition);
}
var bouncedColor = Vec3.Zero;
if (result.Source)
{
bouncedColor = result.Color;
}
else if (DistanceTraveled < maximum)
{
var colorSum = Vec3.Zero;
Vec3 target = result.Normal + Vec3.Random();
// Linearly interpolate between the perfect reflection and the scattered normal.
if (ThreadSafeRandom.NextDouble() < result.Reflectance)
{
var reflectionTarget = Direction - 2 * result.Normal * result.Normal.Dot(Direction);
target = reflectionTarget * (1 - result.Roughness) + target * result.Roughness;
}
var ray = new Ray(CurrentPosition + result.Normal * minimum * 2, target);
var reflectionResult = ray.March(field, minimum, maximum - DistanceTraveled, fog);
var rAmount = Utils.Interpolate(result.Color.X, 1, result.Reflectance);
var gAmount = Utils.Interpolate(result.Color.Y, 1, result.Reflectance);
var bAmount = Utils.Interpolate(result.Color.Z, 1, result.Reflectance);
bouncedColor = new Vec3(
reflectionResult.Color.X * rAmount * (1 - result.Absorbance),
reflectionResult.Color.Y * gAmount * (1 - result.Absorbance),
reflectionResult.Color.Z * bAmount * (1 - result.Absorbance)
);
}
else
{
bouncedColor = new Vec3(1.0, 0.0, 0.0);
}
var fogAmount = DistanceTraveled / maximum;
if (maximum == 0)
{
fogAmount = 1;
}
result.Color = Utils.Interpolate(bouncedColor, fog, fogAmount);
return(result);
}
public Ray(Vec3 position, Vec3 direction)
{
CurrentPosition = position;
Direction = direction.Normalize();
DistanceTraveled = 0;
}