internal Color ShadeHit(IntersectionState state, int maxRecursion = MaxRecursion)
{
Color surfaceColor = Colors.Black;
foreach (Light light in Lights)
{
bool isShadowed = IsShadowed(state.OverPoint, light);
Color surfaceColorFromLight = state.Shape.Material.CalculateLighting(
state.Shape,
light,
state.OverPoint,
state.Eye,
state.Normal,
isShadowed);
surfaceColor += surfaceColorFromLight;
}
Color reflectedColor = ReflectedColor(state, maxRecursion);
Color refractedColor = RefractedColor(state, maxRecursion);
Material material = state.Shape.Material;
if (material.Reflective > 0 && material.Transparency > 0)
{
double reflectance = state.Schlick();
return(surfaceColor + (reflectedColor * reflectance) + (refractedColor * (1 - reflectance)));
}
return(surfaceColor + reflectedColor + refractedColor);
}
public Color ReflectedColor(IntersectionState state, int maxRecursion = MaxRecursion)
{
if (maxRecursion <= 0 || state.Shape.Material.Reflective == 0)
{
return(Colors.Black);
}
var reflectedRay = new Ray(state.OverPoint, state.Reflection);
Color color = ColorAt(reflectedRay, maxRecursion - 1);
Color reflectedColor = color * state.Shape.Material.Reflective;
return(reflectedColor);
}
/// <summary>
/// Finds the color of the first shape that is hit for the given ray.
/// </summary>
/// <param name="ray">The ray to use for hit testing.</param>
/// <param name="maxRecursion">The maximum number of additional rays to use for reflection.</param>
/// <returns>
/// The color for the part of the shape that the ray hits, or <see cref="Colors.Black"/> if no shape is hit.
/// </returns>
public Color ColorAt(Ray ray, int maxRecursion = MaxRecursion)
{
IntersectionList intersections = Intersect(ray);
Intersection? hit = intersections.Hit;
if (hit == null)
{
return(Colors.Black);
}
var state = IntersectionState.Create(hit, ray, intersections);
Color color = ShadeHit(state, maxRecursion);
return(color);
}
public Color RefractedColor(IntersectionState state, int maxRecursion = MaxRecursion)
{
if (maxRecursion <= 0 || state.Shape.Material.Transparency == 0)
{
return(Colors.Black);
}
// Find the ratio of the first index of refraction to the second. This is inverted from the definition of
// Snell's Law, which is sin(theta_i) / sin(theta_t) = n2 / n1.
double nRatio = state.N1 / state.N2;
// cos(theta_i) is the same as the dot product of the two vectors.
double cosI = state.Eye.Dot(state.Normal);
// Find sin(theta_t)^2 via trigonometric identity.
double sin2T = nRatio * nRatio * (1 - (cosI * cosI));
// Total internal reflection - there is no refraction.
if (sin2T > 1)
{
return(Colors.Black);
}
// Find cos(theta_t) via trigonometric identity.
double cosT = Math.Sqrt(1.0 - sin2T);
// Compute the direction of the refracted ray.
Vector direction = (state.Normal * ((nRatio * cosI) - cosT)) - (state.Eye * nRatio);
// Create the refracted ray.
var refractedRay = new Ray(state.UnderPoint, direction);
// Find the color of the refracted ray, making sure to multiply by the transparency value to account for any opacity.
Color color = ColorAt(refractedRay, maxRecursion - 1) * state.Shape.Material.Transparency;
return(color);
}