source: GTP/trunk/App/Demos/Illum/Ogre/src/DiffuseTest/scripts/Hit.txt @ 1712

float3 Hit( float3 x, float3 R, samplerCUBE mp )
{
  
        float rl = readDistanceCubeMap(mp, R); // |r|
        
        float dp = rl - dot(x, R);              // parallax
        
        float3 p = x + R * dp;
        return p;
}
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// This function is called several times.
float3 Hit( float3 x, float3 R, samplerCUBE mp )
{
        float rl = readDistanceCubeMap( mp, R);                         // |r|
        
        float ppp = length( x ) /  readDistanceCubeMap( mp, x);                 // |p|/|p’|
        float dun = 0, pun = ppp, dov = 0, pov = 0;
        float dl = rl * ( 1 - ppp );                                                    // eq. 2
        float3 l = x + R * dl;                                                                  // ray equation

        // iteration
        for( int i = 0; i < 2; i++ )    // 2 !!!!!!!!!!!!!!!!!!!!!!!
        {
                float llp = length( l ) / readDistanceCubeMap( mp, l);          // |l|/|l’|
                if ( llp < 0.999f )                                                                     // undershooting
                {
                        dun = dl; pun = llp;                                                    // last undershooting
                        dl += ( dov == 0 ) ? rl * ( 1 - llp ) :                 // eq. 2
                                ( dl - dov ) * ( 1 - llp ) / ( llp - pov );     // eq. 3
                } else if ( llp > 1.001f )                                                      // overshooting
                {
                        dov = dl; pov = llp;                                                    // last overshooting
                        dl += ( dl -dun ) * ( 1 - llp ) / ( llp - pun );// eq. 3
                }
                l = x + R * dl;                                                                         // ray equation
        }
        return l;                                                                                               // computed hit point
}
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float3 Hit(float3 x, float3 R, samplerCUBE mp)
{
        R = normalize(R);
        float3 xNorm = normalize(x);
        float3 dt = (R - xNorm) / (float) LIN_ITERATIONCOUNT;
        float dx = length(cross(R,x));
        
        float3 pN = normalize(cross(R, xNorm));
        float3 N = normalize(cross(pN,R));
        float d = dot(x, N);    
        
        float3 under = xNorm * readDistanceCubeMap(mp, x);
        float3 over = R * readDistanceCubeMap(mp, R);
        
        //linear iteration      
        for(int i = 1; i < LIN_ITERATIONCOUNT; i++)
        {
                float3 dir = normalize(xNorm + dt * i);
                float dist = readDistanceCubeMap( mp, dir);
                float3 point = dir * dist;
                                
                if( dot(N, point) > d)//undershooting
                {
                        under = point;                  
                }
                else                            //overshooting
                {
                        over = point;                   
                        i = LIN_ITERATIONCOUNT;
                }       
        }
        
        float3 dirUn = normalize(under);
        float3 dirOv = normalize(over);
        float tun = d / dot(N, dirUn);
        float pun = tun / length(under);
        float dun = length(tun * dirUn - x);
        float tov = d / dot(N, dirOv);
        float pov = tov / length(over);
        float dov = length(tov * dirOv - x);
        float tl = (d - dot(N, over)) / dot(N, under - over);
        float3 l = over + tl * (under - over);
        float dl = length(l - x);
                
        //secant iteration
        for( int i = 0; i < SECANT_ITERATIONCOUNT; i++ )
        {
                float llp = length( l ) / readDistanceCubeMap( mp, l);          // |l|/|l’|
                if ( llp < 0.999f )                                                                     // undershooting
                {
                        dun = dl; pun = llp;                                                    // last undershooting
                        dl += ( dl - dov ) * ( 1 - llp ) / ( llp - pov );       // eq. 3
                } else if ( llp > 1.001f )                                                      // overshooting
                {
                        dov = dl; pov = llp;                                                    // last overshooting
                        dl += ( dl - dun ) * ( 1 - llp ) / ( llp - pun );// eq. 3
                }
                l = x + R * dl;                                                                         // ray equation
        }
        
        return l;               
        return over;    
        return (under + over)/2.0;
}
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float3 Hit(float3 x, float3 R, samplerCUBE mp)
{
        //return R + x * 0.0000000001;
        
        R = normalize(R);
        float3 xNorm = normalize(x);
        float3 dt = (R - xNorm) / (float) LIN_ITERATIONCOUNT;
        float dx = length(cross(R,x));
        
        float3 pN = normalize(cross(R, xNorm));
        float3 N = normalize(cross(pN,R));
        float D = dot(x, N);    
        
        float under = readDistanceCubeMap(mp, x);
        float over = readDistanceCubeMap(mp, R);
        float dun = 0;
        float dov = 0;
        float lun = length(x);
        float lov;
        
        float3 l;
        
        //linear iteration      
        for(int i = 1; i < LIN_ITERATIONCOUNT; i++)
        {
        
                l = normalize(xNorm + dt * i);
                float lL = readDistanceCubeMap( mp, l);
                float lambda = D / dot(N, l);
                //float lambda = (dot(x,l) - dot(R,l) * dot(x,R)) / (lL * lL - dot(R,l) * dot(R,l));
                float d = dot(l, R) * lambda - dot(x, R);
                                        
                if( lambda < lL)//undershooting
                {
                        lun = lambda;
                        dun = d;
                        under = lL;                     
                }
                else                            //overshooting
                {
                        lov = lambda;
                        dov = d;
                        over = lL;                      
                        i = LIN_ITERATIONCOUNT;
                }       
        }
        
        if(dov == 0)l = R;
        else l = x + R * dov;
        return l;
        
                
        float pun = lun / length(under);
        float pov;
        float dl;
        
        if(dov == 0)
        {
                dl = over * ( 1 - pun );
        }
        else
        {
                pov = lov / length(over);       
                dl = dun + (dun - dov) * (1 - pun)/(pun - pov);         
        }
        l = x + R * dl; 
                
        //secant iteration
        for( int i = 0; i < SECANT_ITERATIONCOUNT; i++ )
        {
                float llp = length( l ) / readDistanceCubeMap( mp, l);          // |l|/|l’|
                if ( llp < 0.999f )                                                                     // undershooting
                {
                        dun = dl; pun = llp;                                                    // last undershooting
                        dl += ( dov == 0 ) ? over * ( 1 - llp ) :                       // eq. 2
                                ( dl - dov ) * ( 1 - llp ) / ( llp - pov );     // eq. 3
                } else if ( llp > 1.001f )                                                      // overshooting
                {
                        dov = dl; pov = llp;                                                    // last overshooting
                        dl += ( dl -dun ) * ( 1 - llp ) / ( llp - pun );// eq. 3
                }
                l = x + R * dl;                                                                         // ray equation
        }
        
        return l;               
        return over;    
        return (under + over) / 2.0;
}