public override Point Sample(float u1, float u2, out Normal ns)
{
var z = MathUtility.Lerp(u1, _zMin, _zMax);
var t = u2 * _phiMax;
var p = new Point(_radius * MathUtility.Cos(t), _radius * MathUtility.Sin(t), z);
ns = Normal.Normalize(ObjectToWorld.TransformNormal(new Normal(p.X, p.Y, 0)));
if (ReverseOrientation)
ns *= -1.0f;
return ObjectToWorld.TransformPoint(ref p);
}
public override Point Sample(float u1, float u2, out Normal ns)
{
Point p = new Point(0, 0, 0) + _radius * MonteCarloUtilities.UniformSampleSphere(u1, u2);
ns = Normal.Normalize(ObjectToWorld.TransformNormal(new Normal(p.X, p.Y, p.Z)));
if (ReverseOrientation)
{
ns *= -1.0f;
}
return(ObjectToWorld.TransformPoint(ref p));
}
public override SampledSpectrum Sample(ref Vector3 point, Scene scene, out Vector3 incomingVector,
out VisibilityTester visibilityTester)
{
var r1 = StaticRandom.NextFloat() * 2 - 1;
var r2 = StaticRandom.NextFloat() * 2 - 1;
var pointInDiskLocal = new Vector3(r1 * _radius, 0, r2 * _radius);
var pointInDiskWorld = ObjectToWorld.TransformPoint(ref pointInDiskLocal);
incomingVector = point - pointInDiskWorld;
var cosangle = Vector3.Dot(incomingVector.Normalized(), _normal);
visibilityTester = new VisibilityTester(pointInDiskWorld, point, scene);
return(Spectrum * cosangle / incomingVector.Length);
}
public override Point Sample(float u1, float u2, out Normal ns)
{
var p = new Point();
MonteCarloUtilities.ConcentricSampleDisk(u1, u2, out p.X, out p.Y);
p.X *= _radius;
p.Y *= _radius;
p.Z = _height;
ns = Normal.Normalize(ObjectToWorld.TransformNormal(new Normal(0, 0, 1)));
if (ReverseOrientation)
{
ns *= -1.0f;
}
return(ObjectToWorld.TransformPoint(ref p));
}
public override float Pdf(Point p, Vector wi)
{
Point Pcenter = ObjectToWorld.TransformPoint(Point.Zero);
// Return uniform weight if point inside sphere
if (Point.DistanceSquared(p, Pcenter) - _radius * _radius < 1e-4f)
{
return(base.Pdf(p, wi));
}
// Compute general sphere weight
float sinThetaMax2 = _radius * _radius / Point.DistanceSquared(p, Pcenter);
float cosThetaMax = MathUtility.Sqrt(Math.Max(0.0f, 1.0f - sinThetaMax2));
return(MonteCarloUtilities.UniformConePdf(cosThetaMax));
}
public override Point Sample(Point p, float u1, float u2, out Normal ns)
{
// Compute coordinate system for sphere sampling
Point Pcenter = ObjectToWorld.TransformPoint(Point.Zero);
Vector wc = Vector.Normalize(Pcenter - p);
Vector wcX, wcY;
Vector.CoordinateSystem(wc, out wcX, out wcY);
// Sample uniformly on sphere if $\pt{}$ is inside it
if (Point.DistanceSquared(p, Pcenter) - _radius * _radius < 1e-4f)
{
return(Sample(u1, u2, out ns));
}
// Sample sphere uniformly inside subtended cone
float sinThetaMax2 = _radius * _radius / Point.DistanceSquared(p, Pcenter);
float cosThetaMax = MathUtility.Sqrt(Math.Max(0.0f, 1.0f - sinThetaMax2));
DifferentialGeometry dgSphere;
float thit, rayEpsilon;
Point ps;
Ray r = new Ray(p, MonteCarloUtilities.UniformSampleCone(u1, u2, cosThetaMax, ref wcX, ref wcY, ref wc),
1e-3f);
if (!TryIntersect(r, out thit, out rayEpsilon, out dgSphere))
{
thit = Vector.Dot(Pcenter - p, Vector.Normalize(r.Direction));
}
ps = r.Evaluate(thit);
ns = (Normal)Vector.Normalize(ps - Pcenter);
if (ReverseOrientation)
{
ns *= -1.0f;
}
return(ps);
}
