public override bool IntersectP(Ray r)
{
var ray = new Ray ();
this.WorldToObject.Apply (r, ref ray);
if (Math.Abs (ray.Direction.z) < 1e-7) return false;
var thit = (height - ray.Origin.z) / ray.Direction.z;
if (thit < ray.MinT || thit > ray.MaxT)
return false;
var phit = ray.Apply (thit);
var dist2 = phit.x * phit.x + phit.y * phit.y;
if (dist2 > radius * radius || dist2 < innerRadius * innerRadius)
return false;
var phi = Math.Atan2 (phit.y, phit.x);
if (phi < 0) phi += 2.0 * Math.PI;
if (phi > phiMax)
return false;
return true;
}
public override bool Intersect(Ray r, out double tHit, out double rayEpsilon, DifferentialGeometry dg)
{
tHit = 0.0;
rayEpsilon = 0.0;
var ray = new Ray ();
this.WorldToObject.Apply (r, ref ray);
if (Math.Abs (ray.Direction.z) < 1e-7) return false;
var thit = (height - ray.Origin.z) / ray.Direction.z;
if (thit < ray.MinT || thit > ray.MaxT)
return false;
var phit = ray.Apply (thit);
var dist2 = phit.x * phit.x + phit.y * phit.y;
if (dist2 > radius * radius || dist2 < innerRadius * innerRadius)
return false;
var phi = Math.Atan2 (phit.y, phit.x);
if (phi < 0) phi += 2.0 * Math.PI;
if (phi > phiMax)
return false;
var u = phi / phiMax;
var oneMinusV = ((Math.Sqrt (dist2) - innerRadius) /
(radius - innerRadius));
var invOneMinusV = (oneMinusV > 0.0) ? (1.0 / oneMinusV) : 0.0;
var v = 1.0 - oneMinusV;
var dpdu = new Vector (-phiMax * phit.y, phiMax * phit.x, 0.0);
var dpdv = new Vector (-phit.x * invOneMinusV, -phit.y * invOneMinusV, 0.0);
dpdu *= phiMax * Util.InvTwoPI;
dpdv *= (radius - innerRadius) / radius;
var dndu = new Normal (0, 0, 0);
var dndv = new Normal (0, 0, 0);
var o2w = new Transform (this.ObjectToWorld);
dg = new DifferentialGeometry (o2w.Apply (phit), null, null, o2w.Apply (dndu), o2w.Apply (dndv), u, v, this);
tHit = thit;
rayEpsilon = 5e-4 * tHit;
return true;
}
/// <summary>
/// Computes the propability distribution function at the given point
/// </summary>
/// <param name="p">The point to check against</param>
/// <param name="wi">The out vector</param>
/// <returns>The propability distribution function</returns>
public virtual double Pdf (Point p, Vector wi)
{
var dgLight = new DifferentialGeometry ();
var ray = new Ray (p, wi, 1e-3);
ray.Depth = -1;
double thit, rayEpsilon;
if (!this.Intersect (ray, out thit, out rayEpsilon, dgLight))
return 0.0;
var pdf = Util.DistanceSquared (p, ray.Apply (thit)) / (Util.AbsDot (dgLight.nn, -wi) * this.Area);
if (double.IsInfinity (pdf))
pdf = 0.0;
return pdf;
}
