/*==LICENSE==*

CyanWorlds.com Engine - MMOG client, server and tools
Copyright (C) 2011  Cyan Worlds, Inc.

This program 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 3 of the License, or
(at your option) any later version.

This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

Additional permissions under GNU GPL version 3 section 7

If you modify this Program, or any covered work, by linking or
combining it with any of RAD Game Tools Bink SDK, Autodesk 3ds Max SDK,
NVIDIA PhysX SDK, Microsoft DirectX SDK, OpenSSL library, Independent
JPEG Group JPEG library, Microsoft Windows Media SDK, or Apple QuickTime SDK
(or a modified version of those libraries),
containing parts covered by the terms of the Bink SDK EULA, 3ds Max EULA,
PhysX SDK EULA, DirectX SDK EULA, OpenSSL and SSLeay licenses, IJG
JPEG Library README, Windows Media SDK EULA, or QuickTime SDK EULA, the
licensors of this Program grant you additional
permission to convey the resulting work. Corresponding Source for a
non-source form of such a combination shall include the source code for
the parts of OpenSSL and IJG JPEG Library used as well as that of the covered
work.

You can contact Cyan Worlds, Inc. by email legal@cyan.com
 or by snail mail at:
      Cyan Worlds, Inc.
      14617 N Newport Hwy
      Mead, WA   99021

*==LICENSE==*/

#include "HeadSpin.h"

#include "MaxMain/MaxAPI.h"

#include "Shaders.h"

//===========================================================================
// Useful variables...
//===========================================================================

static PhongShader phongShader;
static BlinnShader blinnShader;
static MetalShader metalShader;
static hsMaxShader plasmaShader;

static Shader *shaders[3] = {
        &phongShader,
        &metalShader,
        &blinnShader,
};

AColor black(0.0f,0.0f,0.0f,0.0f);

//===========================================================================
// Useful functions...
//===========================================================================

Shader *GetShader(int s) { return shaders[s]; };

#if 1
// Quadratic
static inline float Soften(float r) {
    return r*(2.0f-r);
}
#else
// Cubic
static inline float Soften(float r) {
    return r*r*(3.0f-2.0f*r);
}
#endif

float CompK(float f0) {
    return float(2.0*sqrt(f0)/sqrt(1.0-f0));
}

float fres_metal(float c, float k) {
    float b,rpl, rpp,c2;
    b = k*k + 1.0f;
    c2 = c*c;
    rpl = (b*c2-2*c+1)/(b*c2+2*c+1);
    rpp = (b-2*c+c2)/(b+2*c+c2);
    return (.5f*(rpl+rpp));
}

//===========================================================================
// Phong shader... don't know if this is ever going to be used
//===========================================================================

void PhongShader::Illum(ShadeContext &sc, SIllumParams &ip) {
    LightDesc *l;
    Color lightCol;
    BOOL is_shiny;
    Point3 R;
    if (is_shiny=(ip.sh_str>0.0f)) 
        R = sc.ReflectVector();
    
    for (int i=0; i<sc.nLights; i++) {
        l = sc.Light(i);
        float NL, diffCoef;
        Point3 L;
        if (l->Illuminate(sc,ip.N,lightCol,L,NL,diffCoef)) {
            // diffuse
            if (NL<=0.0f) 
                continue;
            if (l->affectDiffuse)
                ip.diffIllum += diffCoef*lightCol;
            if (is_shiny&&l->affectSpecular) {
                // specular (Phong) 
                float c = DotProd(L,R);
                if (c>0.0f) {
                    if (ip.softThresh!=0.0&&diffCoef<ip.softThresh) {
                        float r = diffCoef/ip.softThresh;
                        c *= Soften(r);
                    }
                    c = (float)pow((double)c, (double)ip.ph_exp); // could use table lookup for speed
                    ip.specIllum += c*ip.sh_str*lightCol;
                }
            }
        }
    }
    ip.specIllum *= ip.spec; 
}

//===========================================================================
// hsMax shader... write this?
//===========================================================================

void hsMaxShader::Illum(ShadeContext &sc, SIllumParams &ip) {
    LightDesc *l;
    Color lightCol;
    BOOL is_shiny;
    Point3 R;
    if (is_shiny=(ip.sh_str>0.0f)) 
        R = sc.ReflectVector();
    
    for (int i=0; i<sc.nLights; i++) {
        l = sc.Light(i);
        float NL, diffCoef;
        Point3 L;
        if (l->Illuminate(sc,ip.N,lightCol,L,NL,diffCoef)) {
            // diffuse
            if (NL<=0.0f) 
                continue;
            if (l->affectDiffuse)
                ip.diffIllum += diffCoef*lightCol;
            if (is_shiny&&l->affectSpecular) {
                // specular  
                float c = DotProd(L,R);
                if (c>0.0f) {
                    c = (float)pow((double)c, (double)ip.ph_exp); // could use table lookup for speed
                    ip.specIllum += c*ip.sh_str*lightCol;
                }
            }
        }
    }
    ip.specIllum *= ip.spec; 
}

//===========================================================================
// Blinn shader... don't know if this is ever going to be used
//===========================================================================

void BlinnShader::Illum(ShadeContext &sc, SIllumParams &ip) {
    LightDesc *l;
    Color lightCol;
    
    // Blinn style phong
    BOOL is_shiny=(ip.sh_str>0.0f)?1:0; 
    double ph_exp = double(ip.ph_exp)*4.0; // This is to make the hilite compatible with normal phong
    for (int i=0; i<sc.nLights; i++) {
        l = sc.Light(i);
        float NL, diffCoef;
        Point3 L;
        if (l->Illuminate(sc,ip.N,lightCol,L,NL,diffCoef)) {
            // diffuse
            if (NL<=0.0f) 
                continue;
            
            if (l->affectDiffuse)
                ip.diffIllum += diffCoef*lightCol;
            
            // specular (Phong) 
            if (is_shiny&&l->affectSpecular) {
                Point3 H = FNormalize(L-ip.V);
                float c = DotProd(ip.N,H);   
                if (c>0.0f) {
                    if (ip.softThresh!=0.0&&diffCoef<ip.softThresh) {
                        c *= Soften(diffCoef/ip.softThresh);
                    }
                    c = (float)pow((double)c, ph_exp); // could use table lookup for speed
                    ip.specIllum += c*ip.sh_str*lightCol;
                }
            }
        }
    }
    ip.specIllum *= ip.spec; 
}

//===========================================================================
// Metal shader... don't know if this is ever going to be used
//===========================================================================

void MetalShader::Illum(ShadeContext &sc, SIllumParams &ip) {
    LightDesc *l;
    Color lightCol;
    BOOL gotKav = FALSE;
    float kav, fav0, m2inv,NV;
    
    //IPoint2 sp = sc.ScreenCoord();
    
    BOOL is_shiny;
    if (ip.sh_str>0.0f) {
        NV = -DotProd(ip.N,ip.V);  // N dot V: view vector is TOWARDS us.
        is_shiny = 1;
        float r = 1.0f-ip.shine;
        if (r==0.0f) r = .00001f;
        m2inv = 1.0f/(r*r);  
    }
    else 
        is_shiny = 0;
    
    
    for (int i=0; i<sc.nLights; i++) {
        l = sc.Light(i);
        float NL, diffCoef;
        Point3 L;
        
        if (!l->Illuminate(sc,ip.N,lightCol,L,NL,diffCoef)) 
            continue;
        
        // diffuse
        if (NL>0.0f&&l->affectDiffuse)  // TBD is the NL test necessary?
            ip.diffIllum += diffCoef*lightCol;
        
        if (is_shiny&&l->affectSpecular) { // SPECULAR 
            Color fcol;
            float LH,NH,VH;
            float sec2;  // Was double?? TBD
            Point3 H;
            
            if (NV<0.0f) continue;
            
            H = FNormalize(L-ip.V);
            
            LH = DotProd(L,H);  // cos(phi)   
            NH = DotProd(ip.N,H);  // cos(alpha) 
            if (NH==0.0f) continue;
            VH = -DotProd(ip.V,H);
            
            // compute geometrical attenuation factor 
            float G = (NV<NL)? (2.0f*NV*NH/VH): (2.0f*NL*NH/VH);
            if (G>0.0f) {
                // Compute (approximate) indices of refraction
                //  this can be factored out for non-texture-mapped mtls
                if (!gotKav) {
                    fav0 = Intens(ip.diff);
                    if (fav0>=1.0f) fav0 = .9999f;
                    kav = CompK(fav0);  
                    gotKav = TRUE;
                }
                
                float fav = fres_metal(LH,kav);
                float t = (fav-fav0)/(1.0f-fav0);
                fcol = (1.0f-t)*ip.diff + Color(t,t,t);
                
                // Beckman distribution  (from Cook-Torrance paper)
                sec2 = 1.0f/(NH*NH);  // 1/sqr(cos) 
                float D = (.5f/hsConstants::pi<float>)*sec2*sec2*m2inv*(float)exp((1.0f-sec2)*m2inv);
                if (G>1.0f) G = 1.0f;
                float Rs = ip.sh_str*D*G/(NV+.05f); 
                ip.specIllum += fcol*Rs*lightCol;
            }
        } 
    }
    ip.diffIllum *= 1.0f - ip.sh_str;
}


void MetalShader::SetShininess(float shininess, float shineStr) {
    float r = 1.0f-shininess;
    if (r==0.0f) r = .00001f;
    fm2inv = 1.0f/(r*r);  
    fshin_str = shineStr;
}

float MetalShader::EvalHilite(float x) {
    float c = (float)cos(x*hsConstants::pi<float>);
    float sec2 = 1.0f/(c*c);      /* 1/sqr(cos) */
    return fshin_str*(.5f/hsConstants::pi<float>)*sec2*sec2*fm2inv*(float)exp((1.0f-sec2)*fm2inv);
}

