ibdf.inl

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/*
    toxic - A Global Illumination Renderer
    Copyright (C) 2003-2004 Francois Beaune
    Contact: http://toxicengine.sourceforge.net/

    This file is part of toxic.

    toxic is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    toxic is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with toxic; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

inline
sheep::Real IBDF::EvaluateSpecular(const Context &context,
                                   const sheep::Vector3 &incoming,
                                   sheep::Vector3 *outgoing) const
{
    return 0.0;
}

inline
void IBDF::Sample(const Context &context,
                  const sheep::Vector3 &incoming,
                  sheep::Vector3 *outgoing,
                  sheep::Real *prob,
                  sheep::Real *value) const
{
    assert(!IsSpecular());
    assert(incoming.IsUnitLength());
    assert(incoming.m_y > 0.0);
    assert(outgoing);
    assert(prob);
    assert(value);

    const sheep::Real xi1 = context.m_rng->RandomReal1();
    const sheep::Real xi2 = context.m_rng->RandomReal1();

    *outgoing = sheep::CosineHemisphereSampling(xi1, xi2);
    assert(outgoing->IsUnitLength());

    *prob = ComputeScatteringProbability(incoming, *outgoing);

    *value = Evaluate(context, incoming, *outgoing);
}

inline
sheep::Real IBDF::ComputeScatteringProbability(const sheep::Vector3 &incoming,
                                               const sheep::Vector3 &outgoing) const
{
    assert(!IsSpecular());
    assert(incoming.IsUnitLength());
    assert(incoming.m_y > 0.0);
    assert(outgoing.IsUnitLength());
    assert(outgoing.m_y > 0.0);

    // This is due to the cosine hemisphere sampling.
    return outgoing.m_y / sheep::PI;
}

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