118 lines
3.6 KiB
C
118 lines
3.6 KiB
C
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/*
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This file is part of Nori, a simple educational ray tracer
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Copyright (c) 2015 by Wenzel Jakob
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Nori is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License Version 3
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as published by the Free Software Foundation.
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Nori is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <nori/object.h>
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NORI_NAMESPACE_BEGIN
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/**
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* \brief Convenience data structure used to pass multiple
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* parameters to the evaluation and sampling routines in \ref BSDF
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*/
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struct BSDFQueryRecord {
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/// Incident direction (in the local frame)
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Vector3f wi;
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/// Outgoing direction (in the local frame)
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Vector3f wo;
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/// Relative refractive index in the sampled direction
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float eta;
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Point2f uv;
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/// Measure associated with the sample
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EMeasure measure;
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/// Create a new record for sampling the BSDF
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BSDFQueryRecord(const Vector3f &wi)
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: wi(wi), eta(1.f), measure(EUnknownMeasure) { }
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/// Create a new record for querying the BSDF
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BSDFQueryRecord(const Vector3f &wi,
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const Vector3f &wo, EMeasure measure)
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: wi(wi), wo(wo), eta(1.f), measure(measure) { }
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};
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/**
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* \brief Superclass of all bidirectional scattering distribution functions
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*/
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class BSDF : public NoriObject {
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public:
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/**
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* \brief Sample the BSDF and return the importance weight (i.e. the
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* value of the BSDF * cos(theta_o) divided by the probability density
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* of the sample with respect to solid angles).
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*
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* \param bRec A BSDF query record
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* \param sample A uniformly distributed sample on \f$[0,1]^2\f$
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*
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* \return The BSDF value divided by the probability density of the sample
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* sample. The returned value also includes the cosine
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* foreshortening factor associated with the outgoing direction,
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* when this is appropriate. A zero value means that sampling
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* failed.
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*/
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virtual Color3f sample(BSDFQueryRecord &bRec, const Point2f &sample) const = 0;
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/**
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* \brief Evaluate the BSDF for a pair of directions and measure
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* specified in \code bRec
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*
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* \param bRec
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* A record with detailed information on the BSDF query
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* \return
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* The BSDF value, evaluated for each color channel
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*/
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virtual Color3f eval(const BSDFQueryRecord &bRec) const = 0;
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/**
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* \brief Compute the probability of sampling \c bRec.wo
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* (conditioned on \c bRec.wi).
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*
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* This method provides access to the probability density that
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* is realized by the \ref sample() method.
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*
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* \param bRec
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* A record with detailed information on the BSDF query
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*
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* \return
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* A probability/density value expressed with respect
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* to the specified measure
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*/
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virtual float pdf(const BSDFQueryRecord &bRec) const = 0;
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/**
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* \brief Return the type of object (i.e. Mesh/BSDF/etc.)
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* provided by this instance
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* */
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EClassType getClassType() const { return EBSDF; }
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/**
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* \brief Return whether or not this BRDF is diffuse. This
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* is primarily used by photon mapping to decide whether
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* or not to store photons on a surface
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*/
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virtual bool isDiffuse() const { return false; }
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};
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NORI_NAMESPACE_END
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