Photon Mapping : Photon Tracing

Max_Payne · 2005-06-12T17:53:05

It appears my photon map is finally working right. I am now attempting to render an image using "direct visualisation" of the photon map, that is, simply rendering each pixel's color as the product of the material color times the irradiance estimate obtained from the photon map... This seems to result in garbled results (the colors are wrong). The left wall should be red, right wall should be blue, and back wall should be yellow, the floor and ceiling are white. I believe my photon tracing is the function that was wrong, because before I implemented the russian roulette method, I was actually getting somewhat coherent results. If anyone that is knowledgable about photon mapping would like to help by taking a look at my photon tracing code (I believe its rather intuitive to follow), it would be greatly appreciated. void CRenderer::TracePhoton(const CScene& Scene, const CRay& Ray, const CColor3f& Power, unsigned int TraceDepth) { // Make sure the max depth was not exceeded if (TraceDepth > m_MaxDepth) return; // Declare a vector for the intersection point CVector3 Intersect; // Declare a float for the intersection distance float Distance; // Perform ray casting in the scene CSceneObject* pObject = Scene.CastRay(Ray, Intersect, Distance); // Make sure an object was intersected if (!pObject) return; // Get the point attributes at the intersection point SPointAttributes Point = pObject->PointAttributes(Intersect); // Compute the average color at the point float ColorAverage = Point.Color.Average(); // Compute the diffuse reflection probability float ProbDiffuse = Point.Diffuse * ColorAverage; // Compute the specular reflection probability float ProbSpecular = Point.Specular * ColorAverage; // Compute the transmission probability float ProbTransmit = Point.Transparent * ColorAverage; // Obtain a random number in the [0,1] range float RandomValue = RandomFloat(0.0f, 1.0f); // If this photon is to be diffusely reflected if (RandomValue < ProbDiffuse) { // Generate a diffuse reflection vector CVector3 DiffuseDirection = DiffuseVector(Point.Normal); // Compute the diffuse power CColor3f DiffusePower = (Power * Point.Color) / ProbDiffuse; // Trace the diffuse photon TracePhoton(Scene, CRay(Intersect, DiffuseDirection), DiffusePower, TraceDepth + 1); m_PhotonMap.AddPhoton(Intersect, Ray.GetDirection(), Power); } // If this photon is to be specularly reflected else if (RandomValue < ProbDiffuse + ProbSpecular) { // Calculate the reflected direction CVector3 ReflectedDirection = ReflectedVector(Ray.GetDirection(), Point.Normal); // Compute the specular power CColor3f SpecularPower = (Power * Point.Color) / ProbSpecular; // Trace the reflected photon TracePhoton(Scene, CRay(Intersect, ReflectedDirection), SpecularPower, TraceDepth + 1); } // If this photon is to be transmitted else if (RandomValue < ProbDiffuse + ProbSpecular + ProbTransmit) { // Calculate the refracted direction CVector3 RefractedDirection = RefractedVector(Ray.GetDirection(), Point.Normal, Point.Refraction); // Compute the transmitted power CColor3f TransmitPower = (Power * Point.Color) / ProbTransmit; // Trace the refracted ray to get the refracted color TracePhoton(Scene, CRay(Intersect, RefractedDirection), TransmitPower, TraceDepth + 1); } // This photon will be absorbed else { // Add a photon at this point //m_PhotonMap.AddPhoton(Intersect, Ray.GetDirection(), Power); } }

Graphics and GPU Programming Programming

Started by Max_Payne June 11, 2005 04:15 PM

10 comments, last by ApochPiQ 18 years, 10 months ago

cwhite

586

June 12, 2005 03:23 PM

For comparison reasons, here's a page of direct visualization images i generated with the photon mapper I wrote a year ago: clicky

ApochPiQ

23,138

June 12, 2005 05:53 PM

Quote:Original post by Max_Payne
How would you compute the radiance of a purely diffuse surface?

For a pure Lambertian surface, invert each incident photon's direction and weight its energy by the dot product of the inverted direction with the surface normal at the point of incidence.

Wielder of the Sacred Wands
[Work - ArenaNet] [Epoch Language] [Scribblings]

Photon Mapping : Photon Tracing

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Photon Mapping : Photon Tracing

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines