C++ BSDF::Evaluate方法代码示例

void PathCPURenderThread::DirectLightSampling(
		const float u0, const float u1, const float u2,
		const float u3, const float u4,
		const Spectrum &pathThrouput, const BSDF &bsdf,
		const int depth, Spectrum *radiance) {
	PathCPURenderEngine *engine = (PathCPURenderEngine *)renderEngine;
	Scene *scene = engine->renderConfig->scene;
	
	if (!bsdf.IsDelta()) {
		// Pick a light source to sample
		float lightPickPdf;
		const LightSource *light = scene->SampleAllLights(u0, &lightPickPdf);

		Vector lightRayDir;
		float distance, directPdfW;
		Spectrum lightRadiance = light->Illuminate(scene, bsdf.hitPoint,
				u1, u2, u3, &lightRayDir, &distance, &directPdfW);

		if (!lightRadiance.Black()) {
			BSDFEvent event;
			float bsdfPdfW;
			Spectrum bsdfEval = bsdf.Evaluate(lightRayDir, &event, &bsdfPdfW);

			if (!bsdfEval.Black()) {
				const float epsilon = Max(MachineEpsilon::E(bsdf.hitPoint), MachineEpsilon::E(distance));
				Ray shadowRay(bsdf.hitPoint, lightRayDir,
						epsilon,
						distance - epsilon);
				RayHit shadowRayHit;
				BSDF shadowBsdf;
				Spectrum connectionThroughput;
				// Check if the light source is visible
				if (!scene->Intersect(device, false, u4, &shadowRay,
						&shadowRayHit, &shadowBsdf, &connectionThroughput)) {
					const float cosThetaToLight = AbsDot(lightRayDir, bsdf.shadeN);
					const float directLightSamplingPdfW = directPdfW * lightPickPdf;
					const float factor = cosThetaToLight / directLightSamplingPdfW;

					if (depth >= engine->rrDepth) {
						// Russian Roulette
						bsdfPdfW *= Max(bsdfEval.Filter(), engine->rrImportanceCap);
					}

					// MIS between direct light sampling and BSDF sampling
					const float weight = PowerHeuristic(directLightSamplingPdfW, bsdfPdfW);

					*radiance += (weight * factor) * pathThrouput * connectionThroughput * lightRadiance * bsdfEval;
				}
			}
		}
	}
}

void PathHybridState::DirectLightSampling(const PathHybridRenderThread *renderThread,
		const float u0, const float u1, const float u2,
		const float u3, const BSDF &bsdf) {
	if (!bsdf.IsDelta()) {
		PathHybridRenderEngine *renderEngine = (PathHybridRenderEngine *)renderThread->renderEngine;
		Scene *scene = renderEngine->renderConfig->scene;

		// Pick a light source to sample
		float lightPickPdf;
		const LightSource *light = scene->SampleAllLights(u0, &lightPickPdf);

		Vector lightRayDir;
		float distance, directPdfW;
		Spectrum lightRadiance = light->Illuminate(*scene, bsdf.hitPoint.p,
				u1, u2, u3, &lightRayDir, &distance, &directPdfW);

		if (!lightRadiance.Black()) {
			BSDFEvent event;
			float bsdfPdfW;
			Spectrum bsdfEval = bsdf.Evaluate(lightRayDir, &event, &bsdfPdfW);

			if (!bsdfEval.Black()) {
				const float epsilon = Max(MachineEpsilon::E(bsdf.hitPoint.p), MachineEpsilon::E(distance));
				directLightRay = Ray(bsdf.hitPoint.p, lightRayDir,
						epsilon, distance - epsilon);

				const float cosThetaToLight = AbsDot(lightRayDir, bsdf.hitPoint.shadeN);
				const float directLightSamplingPdfW = directPdfW * lightPickPdf;
				const float factor = cosThetaToLight / directLightSamplingPdfW;

				if (depth >= renderEngine->rrDepth) {
					// Russian Roulette
					bsdfPdfW *= RenderEngine::RussianRouletteProb(bsdfEval, renderEngine->rrImportanceCap);
				}

				// MIS between direct light sampling and BSDF sampling
				const float weight = PowerHeuristic(directLightSamplingPdfW, bsdfPdfW);

				directLightRadiance = (weight * factor) * throuput * lightRadiance * bsdfEval;
			} else
				directLightRadiance = Spectrum();
		} else
			directLightRadiance = Spectrum();
	} else
		directLightRadiance = Spectrum();
}

void LightCPURenderThread::ConnectToEye(const float u0,
		const BSDF &bsdf, const Point &lensPoint, const Spectrum &flux,
		vector<SampleResult> &sampleResults) {
	LightCPURenderEngine *engine = (LightCPURenderEngine *)renderEngine;
	Scene *scene = engine->renderConfig->scene;

	Vector eyeDir(bsdf.hitPoint - lensPoint);
	const float eyeDistance = eyeDir.Length();
	eyeDir /= eyeDistance;

	BSDFEvent event;
	Spectrum bsdfEval = bsdf.Evaluate(-eyeDir, &event);

	if (!bsdfEval.Black()) {
		const float epsilon = Max(MachineEpsilon::E(lensPoint), MachineEpsilon::E(eyeDistance));
		Ray eyeRay(lensPoint, eyeDir,
				epsilon,
				eyeDistance - epsilon);

		float scrX, scrY;
		if (scene->camera->GetSamplePosition(lensPoint, eyeDir, eyeDistance, &scrX, &scrY)) {
			RayHit eyeRayHit;
			BSDF bsdfConn;
			Spectrum connectionThroughput;
			if (!scene->Intersect(device, true, u0, &eyeRay, &eyeRayHit, &bsdfConn, &connectionThroughput)) {
				// Nothing was hit, the light path vertex is visible

				const float cosToCamera = Dot(bsdf.shadeN, -eyeDir);
				const float cosAtCamera = Dot(scene->camera->GetDir(), eyeDir);

				const float cameraPdfW = 1.f / (cosAtCamera * cosAtCamera * cosAtCamera *
					scene->camera->GetPixelArea());
				const float cameraPdfA = PdfWtoA(cameraPdfW, eyeDistance, cosToCamera);
				const float fluxToRadianceFactor = cameraPdfA;

				const Spectrum radiance = connectionThroughput * flux * fluxToRadianceFactor * bsdfEval;

				AddSampleResult(sampleResults, PER_SCREEN_NORMALIZED, scrX, scrY,
						radiance, 1.f);
			}
		}
	}
}