// Obtain the colour of a ray/model intersection
public Colour Shade(Intersection hit, Ray r, int level, double weight)
{
if (level > traceMax)
{
return(background); // Too deep
}
// Get the surface normal
var normal = hit.Model.Normal(hit.Location);
// If looking at the inside of a model (e.g. rhs of CSGDifference; or transparent object)
// then the normal will be inverted
if ((normal * r.Direction) > 0.0)
{
normal = -normal;
}
var colour = new Colour();
// Point p, where shadow ray originates, is elevated from the model
// surface to prevent erroneous self-shadowing.
var p = hit.Location + normal * rayOffset;
var filter = new Colour(1.0);
foreach (var l in lights)
{
// If shadowing, determine if l is blocked
// If only blocked by transparent objects then return the
// overall filter colour in filter;
if (!(shadow && Shadowed(p, l, out filter)))
{
colour += (filter * (l.Illumination(hit, normal)));
}
}
var materialHit = hit.Model.Material;
if (materialHit == null)
{
materialHit = Material.NullMaterial;
}
// Add ambient light
colour += ambient * materialHit.GetPigment(hit.Location);
var reflectance = materialHit.Reflectance;
// Do reflections, but only if they will make a visible contribution
if ((reflectance != 0.0) &&
(reflectance * weight > minWeight) &&
(level <= traceMax))
{
// launch reflected ray from rayOffset above the surface
var rray = new Ray(hit.Location + normal * rayOffset,
(normal * (-2.0 * (r.Direction * normal)) +
r.Direction));
var rhit = Intersect(rray);
if (rhit.Model != null)
{
if (rhit.Model.Material == null)
{
throw new AuroraException("Scene.Trace Model has null material");
}
colour += Shade(rhit, rray, level + 1, reflectance * weight) *
reflectance;
}
// Reflected into space
else
{
colour += background * reflectance;
}
}
if (materialHit.Transparent)
{
// The transmitted (or internally reflected) ray
Ray tray;
// The medium for tray
var medium = materialHit;
if (materialHit.Ior != hit.Medium.Ior) // Refracted?
{
var eta = hit.Medium.Ior / materialHit.Ior;
var ci = normal * -r.Direction;
var disc = 1.0 + eta * eta * (ci * ci - 1.0);
// disc discriminates between refraction and tir
if (disc < 0.0)
{
// TODO: Why did this originally just return White?
// Total internal reflection
// launch transmitted ray from rayOffset above the surface
tray = new Ray(hit.Location + normal * rayOffset, (normal * (-2.0 * (r.Direction * normal)) + r.Direction));
medium = hit.Medium;
// return new Colour(1.0, 1.0, 0.0);
}
else
{
// Refraction
// launch transmitted ray from rayOffset beyond the surface
var tdir = (eta * r.Direction + (eta * ci - Math.Sqrt(disc)) * normal).Normalise();
tray = new Ray(hit.Location + tdir * rayOffset, tdir);
}
}
else
{
// Simple transmission (identical refractive indices)
tray = new Ray(hit.Location + r.Direction * rayOffset, r.Direction);
}
var thit = Intersect(tray);
if (thit.Model != null)
{
var w = medium.Filter.Lightness() * weight;
colour += Shade(thit, tray, level + 1, w) * medium.Filter;
}
else
{
colour += background * medium.Filter;
}
}
return(colour);
}
public void MakeTransparent(Colour tfilter, double tior)
{
filter = tfilter;
ior = tior;
transparent = true;
}
public Pigment(Colour d)
{
a = d;
}
public Material(Colour c, Finish f) : this(new Pigment(c), f)
{
}
