Patch by Tom Kazimiers: automatically cancel photon gathering if few or no photons are being generated

include/mitsuba/render/gatherproc.h

@@ -53,12 +53,15 @@ public:
 	 * \param isLocal
 	 *     Should the parallel process only be executed locally? (sending
 	 *     photons over the network may be unnecessary and wasteful)
+	 * \param autoCancel
+	 *     Indicates if the gathering process should be canceled if there
+	 *     are not enough photons generated
 	 * \param progressReporterPayload
 	 *    Custom pointer payload to be delivered with progress messages
 	 */
 	GatherPhotonProcess(EGatherType type, size_t photonCount, 
 		size_t granularity, int maxDepth, int rrDepth, bool isLocal,
-		const void *progressReporterPayload);
+		bool autoCancel, const void *progressReporterPayload);
 
 	/**
 	 * Once the process has finished, this returns a reference 
@@ -89,6 +92,7 @@ public:
 	bool isLocal() const;
 	ref<WorkProcessor> createWorkProcessor() const; 
 	void processResult(const WorkResult *wr, bool cancelled);
+	EStatus generateWork(WorkUnit *unit, int worker);
 
 	/// @}
 	// ======================================================================
@@ -97,12 +101,23 @@ public:
 protected:
 	/// Virtual destructor
 	virtual ~GatherPhotonProcess() { }
+
+	/**
+	 * \brief Checks if the configuration of needed, generated and shot
+	 * photons indicates an unsuccessful progress of the gathering. This
+	 * check is taken from PBRT.
+	 */
+	inline bool unsuccessful(size_t needed, size_t gen, size_t shot) {
+		return (gen < needed && (gen == 0 || gen < shot/1024));
+	}
 protected:
 	EGatherType m_type;
 	ref<PhotonMap> m_photonMap;
+	size_t m_photonCount;
 	int m_maxDepth;
 	int m_rrDepth;
 	bool m_isLocal;
+	bool m_autoCancel;
 	size_t m_excess, m_numShot;
 };
 

src/integrators/photonmapper/photonmapper.cpp

@@ -60,6 +60,8 @@ public:
 		m_volumeLookupSize = props.getInteger("volumeLookupSize", 120);
 		/* Should photon gathering steps exclusively run on the local machine? */
 		m_gatherLocally = props.getBoolean("gatherLocally", true);
+		/* Indicates if the gathering steps should be canceled if not enough photons are generated. */
+		m_autoCancelGathering = props.getBoolean("autoCancelGathering", true);
 	}
 
 	/// Unserialize from a binary data stream
@@ -77,6 +79,7 @@ public:
 		m_causticLookupSize = stream->readInt();
 		m_volumeLookupSize = stream->readInt();
 		m_gatherLocally = stream->readBool();
+		m_autoCancelGathering = stream->readBool();
 	}
 
 	void serialize(Stream *stream, InstanceManager *manager) const {
@@ -93,6 +96,7 @@ public:
 		stream->writeInt(m_causticLookupSize);
 		stream->writeInt(m_volumeLookupSize);
 		stream->writeBool(m_gatherLocally);
+		stream->writeBool(m_autoCancelGathering);
 	}
 
 	/// Configure the sampler for a specified amount of direct illumination samples
@@ -142,7 +146,8 @@ public:
 			/* Generate the global photon map */
 			ref<GatherPhotonProcess> proc = new GatherPhotonProcess(
 				GatherPhotonProcess::ESurfacePhotons, m_globalPhotons,
-				m_granularity, m_maxDepth, m_rrDepth, m_gatherLocally, job);
+				m_granularity, m_maxDepth, m_rrDepth, m_gatherLocally,
+				m_autoCancelGathering, job);
 
 			proc->bindResource("scene", sceneResID);
 			proc->bindResource("camera", cameraResID);
@@ -172,7 +177,8 @@ public:
 			/* Generate the caustic photon map */
 			ref<GatherPhotonProcess> proc = new GatherPhotonProcess(
 				GatherPhotonProcess::ECausticPhotons, m_causticPhotons,
-				m_granularity, 2, m_rrDepth, m_gatherLocally, job);
+				m_granularity, 2, m_rrDepth, m_gatherLocally,
+				m_autoCancelGathering, job);
 
 			proc->bindResource("scene", sceneResID);
 			proc->bindResource("camera", cameraResID);
@@ -199,7 +205,8 @@ public:
 			/* Generate the volume photon map */
 			ref<GatherPhotonProcess> proc = new GatherPhotonProcess(
 				GatherPhotonProcess::EVolumePhotons, m_volumePhotons,
-				m_granularity, m_maxDepth, m_rrDepth, m_gatherLocally, job);
+				m_granularity, m_maxDepth, m_rrDepth, m_gatherLocally,
+				m_autoCancelGathering, job);
 
 			proc->bindResource("scene", sceneResID);
 			proc->bindResource("camera", cameraResID);
@@ -426,6 +433,7 @@ private:
 	int m_rrDepth;
 	int m_maxDepth, m_maxSpecularDepth;
 	bool m_gatherLocally;
+	bool m_autoCancelGathering;
 };
 
 MTS_IMPLEMENT_CLASS_S(PhotonMapIntegrator, false, SampleIntegrator)

src/integrators/photonmapper/ppm.cpp

@@ -63,6 +63,8 @@ public:
 		m_rrDepth = props.getInteger("rrDepth", 3);
 		/* Block size used to parallelize the photon query passes (default: 32x32 pixels). */
 		m_blockSize = props.getInteger("blockSize", 32);
+		/* Indicates if the gathering steps should be canceled if not enough photons are generated. */
+		m_autoCancelGathering = props.getBoolean("autoCancelGathering", true);
 		m_mutex = new Mutex();
 #if defined(__OSX__)
 		Log(EError, "Progressive photon mapping currently doesn't work "
@@ -277,7 +279,8 @@ public:
 		/* Generate the global photon map */
 		ref<GatherPhotonProcess> proc = new GatherPhotonProcess(
 			GatherPhotonProcess::EAllSurfacePhotons, m_photonCount,
-			m_granularity, m_maxDepth == -1 ? -1 : (m_maxDepth-1), m_rrDepth, true, job);
+			m_granularity, m_maxDepth == -1 ? -1 : (m_maxDepth-1), m_rrDepth, true,
+			m_autoCancelGathering, job);
 
 		proc->bindResource("scene", sceneResID);
 		proc->bindResource("camera", cameraResID);
@@ -351,6 +354,7 @@ private:
 	size_t m_totalEmitted;
 	int m_blockSize;
 	bool m_running;
+	bool m_autoCancelGathering;
 };
 
 MTS_IMPLEMENT_CLASS_S(ProgressivePhotonMapIntegrator, false, Integrator)

src/integrators/photonmapper/sppm.cpp

@@ -64,6 +64,8 @@ public:
 		m_rrDepth = props.getInteger("rrDepth", 3);
 		/* Block size used to parallelize the photon query passes (default: 32x32 pixels). */
 		m_blockSize = props.getInteger("blockSize", 32);
+		/* Indicates if the gathering steps should be canceled if not enough photons are generated. */
+		m_autoCancelGathering = props.getBoolean("autoCancelGathering", true);
 		m_mutex = new Mutex();
 #if defined(__OSX__)
 		Log(EError, "Stochastic progressive photon mapping currently doesn't work "
@@ -265,7 +267,8 @@ public:
 		/* Generate the global photon map */
 		ref<GatherPhotonProcess> proc = new GatherPhotonProcess(
 			GatherPhotonProcess::EAllSurfacePhotons, m_photonCount,
-			m_granularity, m_maxDepth-1, m_rrDepth, true, job);
+			m_granularity, m_maxDepth-1, m_rrDepth, true,
+			m_autoCancelGathering, job);
 
 		proc->bindResource("scene", sceneResID);
 		proc->bindResource("camera", cameraResID);
@@ -339,6 +342,7 @@ private:
 	size_t m_totalEmitted;
 	int m_blockSize;
 	bool m_running;
+	bool m_autoCancelGathering;
 };
 
 MTS_IMPLEMENT_CLASS_S(StochasticProgressivePhotonMapIntegrator, false, Integrator)

src/librender/gatherproc.cpp

@@ -169,10 +169,11 @@ protected:
 };
 
 GatherPhotonProcess::GatherPhotonProcess(EGatherType type, size_t photonCount, 
-	size_t granularity, int maxDepth, int rrDepth, bool isLocal, const void *progressReporterPayload) 
+	size_t granularity, int maxDepth, int rrDepth, bool isLocal, bool autoCancel,
+	const void *progressReporterPayload)
 	: ParticleProcess(ParticleProcess::EGather, photonCount, granularity, "Gathering photons", 
-	  progressReporterPayload), m_type(type), m_maxDepth(maxDepth), m_rrDepth(rrDepth),
+	  progressReporterPayload), m_type(type), m_photonCount(photonCount), m_maxDepth(maxDepth),
-	  m_isLocal(isLocal), m_excess(0), m_numShot(0) {
+	  m_rrDepth(rrDepth),  m_isLocal(isLocal), m_autoCancel(autoCancel), m_excess(0), m_numShot(0) {
 	m_photonMap = new PhotonMap(photonCount);
 }
 	
@@ -211,6 +212,16 @@ void GatherPhotonProcess::processResult(const WorkResult *wr, bool cancelled) {
 	m_resultMutex->unlock();
 }
 
+ParallelProcess::EStatus GatherPhotonProcess::generateWork(WorkUnit *unit, int worker) {
+	/* Use the same approach as PBRT for auto canceling */
+	if (m_autoCancel && m_numShot > 500000
+			&& unsuccessful(m_photonCount, m_photonMap->getPhotonCount(), m_numShot)) {
+		Log(EInfo, "Not enough photons could be collected, giving up");
+		return EFailure;
+	}
+
+	return ParticleProcess::generateWork(unit, worker);
+}
 
 MTS_IMPLEMENT_CLASS(GatherPhotonProcess, false, ParticleProcess) 
 MTS_IMPLEMENT_CLASS_S(GatherPhotonWorker, false, ParticleTracer)