add temperature sample logic for vdbvolume

cuteday · Nov 6, 2023 · 0bbc230 · 0bbc230
1 parent 130a5b1
commit 0bbc230
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Showing 5 changed files with 70 additions and 8 deletions.
diff --git a/src/core/scenegraph.h b/src/core/scenegraph.h
@@ -162,13 +162,14 @@ class VDBVolume : public Volume {
 public:
 	using SharedPtr = std::shared_ptr<VDBVolume>;
 
-	VDBVolume(RGB sigma_a, RGB sigma_s, float g, fs::path density) :
+	VDBVolume(RGB sigma_a, RGB sigma_s, float g, fs::path filepath) :
 		sigma_a(sigma_a), sigma_s(sigma_s), g(g) {
-		densityGrid = loadNanoVDB(density);
+		densityGrid = loadNanoVDB(filepath);
 	}
 
-	VDBVolume(RGB sigma_a, RGB sigma_s, float g, NanoVDBGrid::SharedPtr density) :
-		sigma_a(sigma_a), sigma_s(sigma_s), g(g), densityGrid(density) {}
+	VDBVolume(RGB sigma_a, RGB sigma_s, float g, 
+		NanoVDBGrid::SharedPtr density, NanoVDBGrid::SharedPtr temperature = nullptr) :
+		sigma_a(sigma_a), sigma_s(sigma_s), g(g), densityGrid(density), temperatureGrid(temperature) {}
 
 	virtual std::shared_ptr<SceneGraphLeaf> clone() override;
 	virtual AABB getLocalBoundingBox() const override { return densityGrid->getBounds(); }
@@ -178,6 +179,7 @@ class VDBVolume : public Volume {
 	RGB sigma_s;
 	float g;
 	NanoVDBGrid::SharedPtr densityGrid;
+	NanoVDBGrid::SharedPtr temperatureGrid;
 
 protected:
 	friend class SceneGraph;

diff --git a/src/render/media.cpp b/src/render/media.cpp
@@ -66,6 +66,15 @@ NanoVDBMedium::NanoVDBMedium(const Affine3f &transform, RGB sigma_a, RGB sigma_s
 	majorantGrid	 = MajorantGrid(densityGrid.getBounds(), majorantGridRes);
 }
 
+NanoVDBMedium::NanoVDBMedium(const Affine3f &transform, RGB sigma_a, RGB sigma_s, float g,
+							 NanoVDBGrid density, NanoVDBGrid temperature, const RGBColorSpace *colorSpace) :
+	transform(transform), phase(g), sigma_a(sigma_a), sigma_s(sigma_s), densityGrid(std::move(density)), 
+	temperatureGrid(std::move(temperature)), colorSpace(colorSpace) {
+	inverseTransform = transform.inverse();
+	const Vector3f majorantGridRes{64, 64, 64};
+	majorantGrid	 = MajorantGrid(densityGrid.getBounds(), majorantGridRes);
+}
+
 void NanoVDBMedium::initializeFromHost() {
 	densityGrid.toDevice();
 	initializeMajorantGrid(majorantGrid, densityGrid.getFloatGrid());

diff --git a/src/render/media.h b/src/render/media.h
@@ -139,12 +139,19 @@ class NanoVDBMedium {
 	NanoVDBMedium(const Affine3f &transform, RGB sigma_a, RGB sigma_s, float g,
 				  NanoVDBGrid density, const RGBColorSpace *colorSpace = KRR_DEFAULT_COLORSPACE);
 
+	NanoVDBMedium(const Affine3f &transform, RGB sigma_a, RGB sigma_s, float g, NanoVDBGrid density,
+				  NanoVDBGrid temperature, const RGBColorSpace *colorSpace = KRR_DEFAULT_COLORSPACE);
+
 	KRR_HOST void initializeFromHost();
 
 	KRR_CALLABLE bool isEmissive() const { return false; }
 
 	KRR_CALLABLE Spectrum Le(Vector3f p, const SampledWavelengths &lambda) const {
-		return Spectrum::Zero();
+		if (!temperatureGrid) return Spectrum::Zero();
+		p = inverseTransform * p;
+		float temp = temperatureGrid.getDensity(p);
+		if (temp <= 100.f) return SampledSpectrum(0);
+		return BlackbodySpectrum(temp).sample(lambda);
 	}
 
 	KRR_CALLABLE MediumProperties samplePoint(Vector3f p, const SampledWavelengths &lambda) const { 
@@ -169,6 +176,7 @@ class NanoVDBMedium {
 	}
 
 	NanoVDBGrid densityGrid;
+	NanoVDBGrid temperatureGrid;
 	MajorantGrid majorantGrid;
 	Affine3f transform, inverseTransform;
 	HGPhaseFunction phase;

diff --git a/src/render/spectrum.h b/src/render/spectrum.h
@@ -10,6 +10,7 @@
 KRR_NAMESPACE_BEGIN
 
 class RGBColorSpace;
+class BlackbodySpectrum;
 class RGBBoundedSpectrum;
 class RGBUnboundedSpectrum;
 class DenselySampledSpectrum;
@@ -78,15 +79,53 @@ class SampledSpectrum : public Array<float, nSpectrumSamples> {
 };
 
 class Spectra :
-	public TaggedPointer<RGBBoundedSpectrum, RGBUnboundedSpectrum, DenselySampledSpectrum,
-						 PiecewiseLinearSpectrum> {
+	public TaggedPointer<BlackbodySpectrum, RGBBoundedSpectrum, RGBUnboundedSpectrum, 
+						DenselySampledSpectrum, PiecewiseLinearSpectrum> {
 public:
 	using TaggedPointer::TaggedPointer;
 	KRR_HOST_DEVICE float operator()(float lambda) const;
 	KRR_HOST_DEVICE float maxValue() const;
 	KRR_HOST_DEVICE SampledSpectrum sample(const SampledWavelengths &lambda) const;
 };
 
+class BlackbodySpectrum {
+public:
+	KRR_CALLABLE BlackbodySpectrum(float T) : T(T) {
+		// Compute blackbody normalization constant for given temperature
+		float lambdaMax		= 2.8977721e-3f / T;
+		normalizationFactor = 1 / blackbody(lambdaMax * 1e9f, T);
+	}
+
+	KRR_CALLABLE float operator()(float lambda) const { 
+		return blackbody(lambda, T) * normalizationFactor; 
+	}
+
+	KRR_CALLABLE SampledSpectrum sample(const SampledWavelengths &lambda) const {
+		SampledSpectrum s;
+		for (int i = 0; i < SampledSpectrum::dim; ++i)
+			s[i] = blackbody(lambda[i], T) * normalizationFactor;
+		return s;
+	}
+
+	KRR_CALLABLE float maxValue() const { return 1.f; }
+
+	static KRR_CALLABLE float blackbody(float lambda, float T) {
+		if (T <= 0) return 0;
+		const float c  = 299792458.f;
+		const float h  = 6.62606957e-34f;
+		const float kb = 1.3806488e-23f;
+		// Return emitted radiance for blackbody at wavelength _lambda_
+		float l	 = lambda * 1e-9f;
+		float Le = (2 * h * c * c) / (pow5(l) * (expf((h * c) / (l * kb * T)) - 1));
+		DCHECK(!isnan(Le));
+		return Le;
+	}
+
+private:
+	float T;
+	float normalizationFactor;
+};
+
 class RGBBoundedSpectrum {
 public:
 	KRR_CALLABLE float operator()(float lambda) const { return rsp(lambda); }

diff --git a/src/util/volume.h b/src/util/volume.h
@@ -18,6 +18,8 @@ class NanoVDBGrid {
 	using SharedPtr  = std::shared_ptr<NanoVDBGrid>;
 	using VDBSampler = nanovdb::SampleFromVoxels<nanovdb::FloatGrid::TreeType, 1, false>;
 
+	NanoVDBGrid() = default;
+
 	NanoVDBGrid(nanovdb::GridHandle<nanovdb::CudaDeviceBuffer>&& density, float maxDensity) :
 		densityHandle(std::move(density)), maxDensity(maxDensity) {
 		densityGrid						   = densityHandle.grid<float>();
@@ -35,6 +37,8 @@ class NanoVDBGrid {
 
 	void toDevice() { densityHandle.deviceUpload(); }
 
+	KRR_CALLABLE operator bool() const { return densityGrid != nullptr; }
+
 	KRR_CALLABLE AABB3f getBounds() const { return bounds; }
 
 	KRR_CALLABLE float getDensity(const Vector3f &p) const {
@@ -49,7 +53,7 @@ class NanoVDBGrid {
 
 private:
 	AABB3f bounds;
-	nanovdb::GridHandle<nanovdb::CudaDeviceBuffer> densityHandle;
+	nanovdb::GridHandle<nanovdb::CudaDeviceBuffer> densityHandle{};
 	nanovdb::FloatGrid *densityGrid{nullptr};
 	float maxDensity{0};
 };