/// <inheritdoc />
public override void Pdf_We(Ray ray, out double pdfPos, out double pdfDir)
{
// Interpolate camera matrix and fail if $\w{}$ is not 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)
{
pdfPos = pdfDir = 0.0;
return;
}
// Map ray $(\p{}, \w{})$ onto the raster grid
Point3D pFocus = ray.AtPoint((LensRadius > 0.0 ? FocalDistance : 1.0) / cosTheta);
Point3D pRaster = RasterToCamera.Inverse().ExecuteTransform(c2w.Inverse().ExecuteTransform(pFocus));
// Return zero probability for out of bounds points
Bounds2I sampleBounds = Film.GetSampleBounds();
if (pRaster.X < sampleBounds.MinPoint.X || pRaster.X >= sampleBounds.MaxPoint.X ||
pRaster.Y < sampleBounds.MinPoint.Y || pRaster.Y >= sampleBounds.MaxPoint.Y)
{
pdfPos = pdfDir = 0.0;
return;
}
// Compute lens area of perspective camera
double lensArea = LensRadius != 0.0 ? (Math.PI * LensRadius * LensRadius) : 1.0;
pdfPos = 1.0 / lensArea;
pdfDir = 1.0 / (_a * cosTheta * cosTheta * cosTheta);
}
/// <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)));
}