private void HandleRefraction(Computations comps, IntersectionCollection xs)
{
var containers = new List<Shape>();
foreach (var intersection in xs.Intersections)
{
if (intersection.T == T)
comps.n1 = containers.Any()
? containers.Last().Material.RefractiveIndex
: 1.0;
if (containers.Contains(intersection.Object))
containers.Remove(intersection.Object);
else
containers.Add(intersection.Object);
if (intersection.T == T)
{
comps.n2 = containers.Any()
? containers.Last().Material.RefractiveIndex
: 1.0;
break;
}
}
}
internal Color RefractedColor(Computations comps, int remaining)
{
if (remaining == 0)
{
return(Color.Black);
}
if (comps.Object.Material.Transparency == 0)
{
return(Color.Black);
}
// Snell's law
var nRatio = comps.n1 / comps.n2;
var cosTheta_i = comps.EyeVector.Dot(comps.NormalVector);
var sinTheta_t_squared = Math.Pow(nRatio, 2) * (1 - Math.Pow(cosTheta_i, 2));
if (sinTheta_t_squared > 1)
{
return(Color.Black);
}
var cosTheta_t = Math.Sqrt(1 - sinTheta_t_squared);
var refractedRayDirection =
comps.NormalVector * (nRatio * cosTheta_i - cosTheta_t) -
comps.EyeVector * nRatio;
var refractedRay = new Ray(comps.UnderPoint, refractedRayDirection);
// Find the color of the refracted ray, making sure to multiply
// by the transparency value to account for any opacity
var color = ColorAt(refractedRay, --remaining) * comps.Object.Material.Transparency;
return(color);
}
internal Color ReflectedColor(Computations comps, int remaining = 1)
{
if (remaining < 1)
{
return(Color.Black);
}
if (comps.Object.Material.Reflective == 0.0)
{
return(Color.Black);
}
var reflectRay = new Ray(comps.OverPoint, comps.ReflectV);
var color = ColorAt(reflectRay, --remaining);
return(color * comps.Object.Material.Reflective);
}
internal Color ShadeHit(Computations comps, int remaining = 1)
{
var isShadowed = IsShadowed(comps.OverPoint);
var surface = comps.Object.Material.Lighting(comps.Object, LightSource, comps.OverPoint, comps.EyeVector, comps.NormalVector, isShadowed);
var reflected = ReflectedColor(comps, remaining);
var refracted = RefractedColor(comps, remaining);
var material = comps.Object.Material;
if (material.Reflective > 0 && material.Transparency > 0)
{
var reflectance = comps.Schlick();
return(surface +
reflected * reflectance +
refracted * (1 - reflectance));
}
return(surface + reflected + refracted);
}
public Computations PrepareComputations(Ray ray, IntersectionCollection xs = null)
{
var c = new Computations();
c.T = T;
c.Object = Object;
c.Point = ray.Position(T);
c.EyeVector = -ray.Direction;
c.NormalVector = Object.NormalAt(c.Point, this);
if (c.NormalVector.Dot(c.EyeVector) < 0)
{
c.Inside = true;
c.NormalVector = -c.NormalVector;
}
c.OverPoint = c.Point + c.NormalVector * C.Epsilon;
c.UnderPoint = c.Point - c.NormalVector * C.Epsilon;
c.ReflectV = ray.Direction.Reflect(c.NormalVector);
xs = xs ?? new IntersectionCollection();
HandleRefraction(c, xs);
return c;
}
