private Vector GetContributionFromLightSourceSampling(IntersectionPoint point, Random rand, Vector pathWeight)
{
//Sample Point on LightSource
var lightPoint = data.LightSource.SampleRandomPointOnLightSource(rand);
Vector directionToLight = (lightPoint.Position - point.Position).Normalize();
//Shadow-Ray-Test: Test is the Point on Lightsource visible from 'point'?
var lightVisiblePoint = this.intersectionFinder.GetIntersectionPoint(new Ray(point.Position, directionToLight));
float DistanceForPoint2PointVisibleCheck = 0.0001f; //Magic Number
bool isVisible = lightVisiblePoint != null && (lightVisiblePoint.Position - lightPoint.Position).Length() < DistanceForPoint2PointVisibleCheck;
if (isVisible == false)
{
return(new Vector(0, 0, 0)); //No contribution, if 'point' is located in shadow
}
//Pathcontribution from Lightsource-Sampling
float cosAtPoint = Math.Max(0, Vector.Dot(point.Normal, directionToLight));
float cosAtLight = Math.Max(0, Vector.Dot(lightPoint.Normal, -directionToLight));
float geometryFactor = cosAtPoint * cosAtLight / (lightPoint.Position - point.Position).SqrLength();
float pdfAFromLightSourceSampling = data.LightSource.PdfA; //This is the PdfA for sampling the lightPoint on the Position lightPoint.Position
Vector contributionFromLightSampling = Vector.Mult(pathWeight, DiffuseBrdf.Evaluate(point)) * geometryFactor * data.LightSource.EmissionPerArea / pdfAFromLightSourceSampling;
//Get PdfA from Brdf-Sampling.
float pdfW = DiffuseBrdf.PdfW(point.Normal, directionToLight);
float continuationPdf = Math.Min(1, point.Color.Max());
//This is the PdfA, to hit the LightSource with Brdf-Sampling and hit the Lightsource on the Position lightPoint.Position
//The Factor "cosAtLight / (lightPoint.Position - point.Position).SqrLength()" is the pdfW to PdfA-Conversionfactor.
//This means, you project to Solid Angle Measure from the Brdf to the surface area measure on the Point on the Light
float pdfAFromBrdfSampling = pdfW * continuationPdf * cosAtLight / (lightPoint.Position - point.Position).SqrLength();
//Heare we have used LightSource-Sampling for the Creation of the Point on the LightSource. So we use pdfAFromLightSourceSampling in the numerator
float misFactor = pdfAFromLightSourceSampling / (pdfAFromLightSourceSampling + pdfAFromBrdfSampling);
contributionFromLightSampling *= misFactor;
return(contributionFromLightSampling);
}
private List <Photon> TracePhoton(Random rand)
{
var lightPoint = this.lightSource.GetRandomPointOnLightSource(rand);
Vector direction = DiffuseBrdf.SampleDirection(lightPoint.Normal, rand);
float pdfW = DiffuseBrdf.PdfW(lightPoint.Normal, direction);
float lambda = Vector.Dot(lightPoint.Normal, direction);
Vector pathWeight = lightPoint.Color * lambda / (lightPoint.PdfA * pdfW);
Ray ray = new Ray(lightPoint.Position, direction);
//PhotonType type = PhotonType.None;
int maxPathLength = 5;
List <Photon> photons = new List <Photon>();
for (int i = 0; i < maxPathLength; i++)
{
var point = this.intersectionFinder.GetIntersectionPoint(ray);
if (point == null)
{
return(photons);
}
photons.Add(new Photon(point.Position, point.Normal, pathWeight / this.photonCount, ray.Direction));
//Abbruch mit Russia Rollete
float continuationPdf = Math.Min(1, point.Color.Max());
if (rand.NextDouble() >= continuationPdf)
{
return(photons); // Absorbation
}
Vector newDirection = DiffuseBrdf.SampleDirection(point.Normal, rand);
pathWeight = Vector.Mult(pathWeight * Vector.Dot(point.Normal, newDirection) / DiffuseBrdf.PdfW(point.Normal, newDirection), DiffuseBrdf.Evaluate(point)) / continuationPdf;
ray = new Ray(point.Position, newDirection);
}
return(photons);
}
private Vector[,] EstimateFrameWithLightracing(int width, int height, Random rand)
{
int lightPathsPerIteration = width * height;
int maxPathLength = 5;
Vector[,] frame = new Vector[width, height];
for (int x = 0; x < width; x++)
{
for (int y = 0; y < height; y++)
{
frame[x, y] = new Vector(0, 0, 0);
}
}
for (int j = 0; j < lightPathsPerIteration; j++)
{
//Sample Position on Lightsource
var point = data.LightSource.SampleRandomPointOnLightSource(rand);
//Pathweight
Vector pathWeight = new Vector(1, 1, 1) * data.LightSource.EmissionPerArea / data.LightSource.PdfA;
//Connect Point on Lightsource with Camera
var c = TryToConnectPointWithCamera(point, pathWeight, lightPathsPerIteration);
if (c != null)
{
frame[c.PixelX, c.PixelY] += c.PathContribution;
}
//Sample Direction from Point on LightSource into scene. Use the diffuse Brdf
Vector direction = DiffuseBrdf.SampleDirection(point.Normal, rand); //Direct vom Point on Light into some point in scene
float pdfW = DiffuseBrdf.PdfW(point.Normal, direction); //PDF with Respect to Solid Angle from 'direction'
//New Pathweight after sampling direction
float cosAtPoint = Math.Max(0, Vector.Dot(point.Normal, direction));
pathWeight *= cosAtPoint / pdfW;
Ray ray = new Ray(point.Position, direction);
for (int k = 1; k < maxPathLength; k++)
{
//Get next intersectionpoint with scene starting from old point-Position
point = this.intersectionFinder.GetIntersectionPoint(ray);
if (point == null)
{
break; //Break Light-Path-Creation
}
//Connect Point in scene with Camera
c = TryToConnectPointWithCamera(point, pathWeight, lightPathsPerIteration);
if (c != null)
{
frame[c.PixelX, c.PixelY] += c.PathContribution;
}
//The Lightsource dosn't reflect light
if (point.IsLocatedOnLightSource)
{
break;
}
//Break with Russia Rollete
float continuationPdf = Math.Min(1, point.Color.Max());
if (rand.NextDouble() >= continuationPdf)
{
break; // Absorbation
}
//Go ahead with lighttracing after connection with camera
direction = DiffuseBrdf.SampleDirection(point.Normal, rand);
pdfW = DiffuseBrdf.PdfW(point.Normal, direction);
cosAtPoint = Math.Max(0, Vector.Dot(point.Normal, direction));
pathWeight = Vector.Mult(pathWeight, DiffuseBrdf.Evaluate(point)) * cosAtPoint / (pdfW * continuationPdf);
ray = new Ray(point.Position, direction);
}
}
return(frame);
}
private Vector EstimateColorWithPathtracing(int x, int y, Random rand)
{
Ray primaryRay = data.Camera.GetPrimaryRay(x, y);
float cosAtCamera = Vector.Dot(primaryRay.Direction, this.data.Camera.Forward);
Vector pathWeight = new Vector(1, 1, 1) * cosAtCamera;
Ray ray = primaryRay;
int maxPathLength = 5;
for (int i = 0; i < maxPathLength; i++)
{
var point = this.intersectionFinder.GetIntersectionPoint(ray);
if (point == null)
{
return(new Vector(0, 0, 0));
}
if (point.IsLocatedOnLightSource && Vector.Dot(point.Normal, -ray.Direction) > 0)
{
pathWeight = Vector.Mult(pathWeight, point.Emission);
return(pathWeight);
}
//Abbruch mit Russia Rollete
float continuationPdf = Math.Min(1, point.Color.Max());
if (rand.NextDouble() >= continuationPdf)
{
return(new Vector(0, 0, 0)); // Absorbation
}
Vector newDirection = DiffuseBrdf.SampleDirection(point.Normal, rand);
pathWeight = Vector.Mult(pathWeight * Vector.Dot(point.Normal, newDirection) / DiffuseBrdf.PdfW(point.Normal, newDirection), DiffuseBrdf.Evaluate(point)) / continuationPdf;
ray = new Ray(point.Position, newDirection);
}
return(new Vector(0, 0, 0));
}
private Vector EstimateColorWithPathtracingWithNextEventEstimation(int x, int y, Random rand)
{
//This is the sum from all Pathcontributions from all Pathlenghts up to maxPathLength
//This means Contribution(C L) + Contribution(C D L) + Contribution(C D D L) + Contribution(C D D D L) + Contribution(C D D D D L)
//For Each Pathlength-Step, the Contribution from Brdf-Sampling and Lightsource-Sampling is added but only one from this two Sampling-Methods
//will create a Contribution != 0. If you hit the Lightsource, then you only get the BrdfSampling-Contribution. The LightSource-Sampling-Contribution
//will be zero because if your running point is on the light and the light don't reflect any light, then you don't can create any more Lightpoints
//If you are on a Point in the Scene (Not Lightsoure) then only the Contribution from Lightsource-Sampling can be greater zero. The Brdf-Sampling
//Contribution (Pathtracing) will be zero.
Vector contributionSum = new Vector(0, 0, 0);
Ray primaryRay = data.Camera.GetPrimaryRay(x, y);
float cosAtCamera = Vector.Dot(primaryRay.Direction, this.data.Camera.Forward);
Vector pathWeight = new Vector(1, 1, 1) * cosAtCamera;
Ray ray = primaryRay;
float pdfW = data.Camera.PdfWForPrimaryRayDirectionSampling(ray.Direction); //This will store the PdfW and Contination Pdf, which was used for Brdf-Sampling
int maxPathLength = 5;
for (int i = 0; i < maxPathLength; i++)
{
IntersectionPoint point = this.intersectionFinder.GetIntersectionPoint(ray);
if (point == null)
{
break; //Ray leave the scene
}
//Try to add Contribution from Brdf-Sampling (This Brdf-Sampling is also called Pathtracing because you do this for every Pathpoint)
if (point.IsLocatedOnLightSource && Vector.Dot(point.Normal, -ray.Direction) > 0)
{
//This is the PdfA on the LightPoint, if you would use LightSource-Sampling, to reach from lastPoint(ray.Origin) to current point 'point'
float pdfAFromLightSourceSampling = data.LightSource.PdfA;
//This is the PdfA on the LightPoint, which you get from BrdfSampling to reach rom lastPoint(ray.Origin) to current point 'point'
float pdfAFromBrdfSampling = pdfW * Vector.Dot(point.Normal, -ray.Direction) / (ray.Origin - point.Position).SqrLength();
//We have used Brdf-Sampling. So the pdfAFromBrdfSampling is in the numerator
float misFactor = pdfAFromBrdfSampling / (pdfAFromLightSourceSampling + pdfAFromBrdfSampling);
Vector contributionFromBrdfSampling = Vector.Mult(pathWeight, point.Emission) * misFactor;
contributionSum += contributionFromBrdfSampling;
break; //The light don't reflect any light. So stop here with Pathtracing
}
//Try to add Contribution from Lightsource-Sampling (This is the Next Event Estimation-Sampling)
contributionSum += GetContributionFromLightSourceSampling(point, rand, pathWeight);
//Stop with Russia Rollete
float continuationPdf = Math.Min(1, point.Color.Max());
if (rand.NextDouble() >= continuationPdf)
{
break; // Absorbation
}
//Sample Direction and try to hit to lightSource
Vector direction = DiffuseBrdf.SampleDirection(point.Normal, rand);
pdfW = DiffuseBrdf.PdfW(point.Normal, direction) * continuationPdf;
float cosAtPoint = Math.Max(0, Vector.Dot(point.Normal, direction));
pathWeight = Vector.Mult(pathWeight, DiffuseBrdf.Evaluate(point)) * cosAtPoint / pdfW; //New Pathweight after Brdf-Sampling
ray = new Ray(point.Position, direction);
}
return(contributionSum);
}
private Vector EstimateColorWithPhotonmapping(int x, int y, Random rand, Photonmap photonmap)
{
Ray primaryRay = data.Camera.GetPrimaryRay(x, y);
float cosAtCamera = Vector.Dot(primaryRay.Direction, this.data.Camera.Forward);
Vector pathWeight = new Vector(1, 1, 1) * cosAtCamera;
var eyePoint = this.intersectionFinder.GetIntersectionPoint(primaryRay);
Vector pixelColor = new Vector(0, 0, 0);
if (eyePoint != null)
{
if (eyePoint.IsLocatedOnLightSource)
{
return(eyePoint.Emission);
}
pathWeight = Vector.Mult(pathWeight, DiffuseBrdf.Evaluate(eyePoint));
//Direct Lighting
var lightPoint = data.LightSource.GetRandomPointOnLightSource(rand);
if (IsVisible(eyePoint.Position, lightPoint.Position))
{
pixelColor += Vector.Mult(pathWeight, lightPoint.Color * GeometryTerm(eyePoint, lightPoint) / lightPoint.PdfA);
}
//Final Gathering
Vector newDirection = DiffuseBrdf.SampleDirection(eyePoint.Normal, rand);
pathWeight = pathWeight * Vector.Dot(eyePoint.Normal, newDirection) / DiffuseBrdf.PdfW(eyePoint.Normal, newDirection);
var finalGatherPoint = this.intersectionFinder.GetIntersectionPoint(new Ray(eyePoint.Position, newDirection));
if (finalGatherPoint != null)
{
//100000 3000 1000
float searchRadius = 0.00634257728f * 2;//0.0383904837f;//0.065260686f;
var photons = photonmap.SearchPhotons(finalGatherPoint, searchRadius);
float kernelFunction = 1.0f / (searchRadius * searchRadius * (float)Math.PI);
foreach (var photon in photons)
{
pixelColor += Vector.Mult(pathWeight, Vector.Mult(DiffuseBrdf.Evaluate(finalGatherPoint), photon.PathWeight) * kernelFunction);
}
}
}
return(pixelColor);
}