/// <inheritdoc />
public override double GenerateRayDifferential(CameraSample sample, out RayDifferential ray)
{
//ProfilePhase prof(Prof::GenerateCameraRay);
// Compute raster and camera sample positions
Point3D pFilm = new Point3D(sample.FilmPoint.X, sample.FilmPoint.Y, 0.0);
Point3D pCamera = RasterToCamera.ExecuteTransform(pFilm);
Vector3D dir = new Vector3D(pCamera.X, pCamera.Y, pCamera.Z).Normalize();
ray = new RayDifferential(new Point3D(0.0, 0.0, 0.0), dir);
// Modify ray for depth of field
if (LensRadius > 0.0)
{
// Sample point on lens
Point2D pLens = LensRadius * Sampling.ConcentricSampleDisk(sample.LensPoint);
// Compute point on plane of focus
double ft = FocalDistance / ray.Direction.Z;
Point3D pFocus = ray.AtPoint(ft);
// Update ray for effect of lens
ray.Origin = new Point3D(pLens.X, pLens.Y, 0.0);
ray.Direction = (pFocus - ray.Origin).ToVector3D().Normalize();
}
// Compute offset rays for _PerspectiveCamera_ ray differentials
if (LensRadius > 0.0)
{
// Compute _PerspectiveCamera_ ray differentials accounting for lens
// Sample point on lens
Point2D pLens = LensRadius * Sampling.ConcentricSampleDisk(sample.LensPoint);
Vector3D dx = (pCamera.ToVector3D() + _dxCamera).Normalize();
double ft = FocalDistance / dx.Z;
Point3D pFocus = new Point3D(0.0, 0.0, 0.0) + (ft * dx).ToPoint3D();
ray.RxOrigin = new Point3D(pLens.X, pLens.Y, 0.0);
ray.RxDirection = (pFocus - ray.RxOrigin).ToVector3D().Normalize();
Vector3D dy = (pCamera.ToVector3D() + _dyCamera).Normalize();
ft = FocalDistance / dy.Z;
pFocus = new Point3D(0.0, 0.0, 0.0) + (ft * dy).ToPoint3D();
ray.RyOrigin = new Point3D(pLens.X, pLens.Y, 0.0);
ray.RyDirection = (pFocus - ray.RyOrigin).ToVector3D().Normalize();
}
else
{
ray.RxOrigin = ray.RyOrigin = ray.Origin;
ray.RxDirection = (pCamera.ToVector3D() + _dxCamera).Normalize();
ray.RyDirection = (pCamera.ToVector3D() + _dyCamera).Normalize();
}
ray.Time = PbrtMath.Lerp(sample.Time, ShutterOpen, ShutterClose);
ray.Medium = Medium;
ray = new RayDifferential(CameraToWorld.ExecuteTransform(ray))
{
HasDifferentials = true
};
return(1.0);
}
/// <inheritdoc />
public override Spectrum We(Ray ray, out Point2D pRaster2)
{
// Interpolate camera matrix and check if $\w{}$ is forward-facing
CameraToWorld.Interpolate(ray.Time, out Transform c2w);
double cosTheta = ray.Direction.Dot(c2w.ExecuteTransform(new Vector3D(0.0, 0.0, 1.0)));
if (cosTheta <= 0.0)
{
pRaster2 = null;
return(Spectrum.Create(0.0));
}
// Map ray $(\p{}, \w{})$ onto the raster grid
Point3D pFocus = ray.AtPoint((LensRadius > 0.0 ? FocalDistance : 1.0) / cosTheta);
Point3D pRaster = RasterToCamera.ExecuteTransform(c2w.Inverse().ExecuteTransform(pFocus));
//Point3D pRaster = Inverse(RasterToCamera)(Inverse(c2w.Inverse)(pFocus));
// Return raster position if requested
pRaster2 = new Point2D(pRaster.X, pRaster.Y);
// Return zero importance for out of bounds points
Bounds2I sampleBounds = Film.GetSampleBounds();
if (pRaster.X < sampleBounds.MinPoint.X || pRaster.Z >= sampleBounds.MaxPoint.X ||
pRaster.Y < sampleBounds.MinPoint.Y || pRaster.Y >= sampleBounds.MaxPoint.Y)
{
return(Spectrum.Create(0.0));
}
// Compute lens area of perspective camera
double lensArea = LensRadius != 0.0 ? (Math.PI * LensRadius * LensRadius) : 1.0;
// Return importance for point on image plane
double cos2Theta = cosTheta * cosTheta;
return(Spectrum.Create(1.0 / (_a * lensArea * cos2Theta * cos2Theta)));
}
