ssBrdf.h

Go to the documentation of this file.

// Copyright JRM Enterprises, Inc. 2011 - 2012
// All rights reserved.
//
// This code is the intellectual property of JRM Enterprises, Inc.
// It may not be used or released as source or compiled binary form
// without the prior written consent of JRM Enterprises, Inc.
//
// Original Author:     Tom Rix     Date: July 2011

#ifndef _ssBrdf_
#define _ssBrdf_


#include "ssdllexport.h"


// class: ssBrdf
//
// description: class to generate brdf specific LUT's
//
class SIGSIMRT_API ssBrdf
{
private:
    static double g(double a, double b);
    static double G(double b) ;
    static double h_Sr(double a, double e);
    static double H_Sr(double a, double e);
    static double H_PhongEven(double a, double n);
    static double H_PhongOdd(double a, double n);
    static double H_PhongAverage(double a, double h);
    static double H_PhongEvenNoN(double a);
    static double H_PhongOddNoN(double a);
    static double H_PhongAverageNoN(double a);
public:

    /* 
     * The SrTable is packed
     * g,G,h,H
     * And assumed to be standard C row major
     *
     * g,    x -> b [0-1], y -> cos (a) [1-0] as a [0 - pi/2]
     * InvG, x -> b [0-1], y -> duplicates 
     * h,    x -> e [0-1], y -> cos (a) [1-0] as a [0 - pi/2] 
     * H,    x -> e [0-1], y -> cos (a) [1-0] as a [0 - pi/2] 
     *
     * h and H are very dependent on e, so the width should be between least 512 - 4096
     * cos (a) does not vary much, so the height should be between 64 - 256
     * both width and height must be greater than 1
     *
     * half_float_overflow_check 
     * If the returned table is to be used as half floats this value should be true
     * Else this value should be false.
     * half floats overflow at 65536.0, when the expontent is too large to store.
     * 
     * returns false if input data is bad.
     */
    
    static bool SrTable (float *t, unsigned int width, unsigned int height, bool half_float_overflow_check = false);

    /*
     * Converts the total dhr into a diffuse reflectance
     */
    static double pd_Sr(double dhr, double percent_specular, double angle_dhr, double grazing_angle_reflectivity);

    /*
     * Converts the total dhr into a specular reflectance
     */
    static double ps_Sr(double dhr, double percent_specular, double angle_dhr, double grazing_angle_reflectivity);

    /*
     * Helper function to return the emissive part of the total dhr.
     * Assumes the material is opaque
     */
    static double pe_Sr(double dhr, double percent_specular, double angle_dhr, double grazing_angle_reflectivity);

    /*
     * Converts angle independent k into angle dependent
     */
    static double K_PhongH (double k, double angle, double grazing_angle_reflection) ;

    /*
     * Recovers the old phong values
     */
    static void RecoverOldPhong (double dhr, double angleDhr, double percentSpecular, double lobe, double *Shine, double* Kamb, double* Kdif, double *Kspec);

    /* 
     * The PhongHTable is packed
     * g,G,1,H
     * And assumed to be standard C row major
     *
     * g,    x -> b [0-1], y -> cos (a) [1-0] as a [0 - pi/2]
     * InvG, x -> b [0-1], y -> duplicates 
     * 1.0
     * H without 1/(n+1), x -> y -> cos(a) [0-1] as a [0 - pi/2] 
     *
     * half_float_overflow_check 
     * If the returned table is to be used as half floats this value should be true
     * Else this value should be false.
     * half floats overflow at 65536.0, when the expontent is too large to store.
     *
     */
    static bool PhongHTable (float *t, unsigned int width, unsigned int height, bool half_float_overflow_check = false);

    /*
     * A complement to the SR and PhongH table
     * Fills a similarly allocaded table with random numbers [0 - 1] 
     * That will be used in the SR calculations
     */
    static bool RoughnessTable (float *t, unsigned int width, unsigned int height);

};

#endif // _ssBrdf_