/////////////////////////////////////////////////////////////////////////////
// velvet.osl - simple smooth velvet surface
//
// Parameters:
//   Ka - scaling of ambient contribution
//   Kd - scaling of diffuse contribution
//   sheen - color of highlight
//   backscatter - controls the retroreflective lobe
//   edginess - how broad the horizon scattering is
//   roughness - how broad the retroreflective lobe is
//
/////////////////////////////////////////////////////////////////////////////
// Copyright 2007 NVIDIA Corporation.  All Rights Reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// 
// * Redistributions of source code must retain the above copyright
//   notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
//   notice, this list of conditions and the following disclaimer in the
//   documentation and/or other materials provided with the distribution.
// * Neither the name of NVIDIA nor the names of its contributors
//   may be used to endorse or promote products derived from this software
//   without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// (This is the Modified BSD License)
/////////////////////////////////////////////////////////////////////////////


#include "material.h"


surface
velvet 
    [[ string description = "Velvet material" ]]
(
    float Ka = 1
        [[  string description = "Ambient scaling",
            float UImin = 0, float UIsoftmax = 1 ]],
    float Kd = 0.5
        [[  string description = "Diffuse scaling",
            float UImin = 0, float UIsoftmax = 1 ]],

    color sheen = .25
        [[ string description = "color of the highlights",
           float UImin = 0, float UImax = 1]],
    float backscatter = 0.1
        [[ string description = "Retroreflective highlight strength",
           float UImin = 0, float UImax = 1 ]],
    float edginess = 10
        [[ string description = "How broad the horizon scattering is",
           float UImin = 0, float UImax = 1 ]],
    float roughness = .1
        [[ string description = "How broad the retroreflective highlight is",
           float UImin = 0, float UImax = 1 ]]
  )
{
    // Construct a frontfacing, unit-length normal
    normal Nf = faceforward (normalize(N), I);

    // Blend ambient, diffuse, and specular lighting
    C = C * (Ka*ambient() + Kd*diffuse(Nf)) +
        LocIllumVelvet (Nf, -normalize(I), sheen, backscatter, edginess, roughness);

    // Scale color by opacity.
    C *= opacity;
}
