private double ComputeLightIntensity(ILight light, Vector3d intersectionPoint, Vector3d normal, Vector3d viewDirection, double specularExponent)
{
if (light is AmbientLight)
{
return(light.Intensity);
}
Vector3d oppositeLightDirection;
double maxDistance;
switch (light)
{
case DirectionalLight directionalLight:
oppositeLightDirection = -directionalLight.Direction;
maxDistance = double.PositiveInfinity;
break;
case PointLight pointLight:
oppositeLightDirection = pointLight.Position - intersectionPoint;
maxDistance = 1d;
break;
default:
throw new NotSupportedException($"Cannot handle light of type {light.GetType().Name}");
}
// shadow
Ray shadowRay = new Ray(intersectionPoint, oppositeLightDirection);
bool hasShadow = shadowRay.HasIntersection(_scene.Objects, RayTracer.Delta, maxDistance);
if (hasShadow)
{
return(0d);
}
double intensity = 0d;
// diffuse
double nl = normal * oppositeLightDirection;
if (nl > 0d)
{
intensity += light.Intensity * nl / (normal.Length * intersectionPoint.Length);
}
// specular
if (specularExponent < 0d)
{
return(intensity);
}
Vector3d lightReflection = oppositeLightDirection.Reflect(normal);
double rv = lightReflection * viewDirection;
if (rv > 0d)
{
intensity += light.Intensity * Math.Pow(rv / (lightReflection.Length * viewDirection.Length), specularExponent);
}
return(intensity);
}