checkLine() (raycast)

DFORCEINLINE bool checkLine(
                    const short *pMap,
                    int p0,
                    int p2,
                    Float3 d,
                    float minY,
                    float maxY,
                    size_t sizL2 )

{
    // y value is in quantized units
    float p1 = (float)pMap[ (p2 << sizL2) + p0 ];

    int coordMax = (int)(1 << sizL2) - 1;

    const float DY_SCA = Terrain::MAP_HE_QUANT_SCALE * Terrain::MAP_HE_QUANT_SCALE;

    u_int   major = 0;

    if ( DAbs( d[2] ) > DAbs( d[0] ) )
    {
        major = 2;
        std::swap( d[0], d[2] );
        std::swap( p0, p2 );
    }

    int     q0      = coordMax;
    int     d0n     = 1;
    float   d1n     = d[1] / d[0] * DY_SCA;
    float   d2n     = d[2] / d[0];

    if ( d[0] < 0 ) {
        q0  = -q0;
        d0n = -d0n;
        d1n = -d1n;
        d2n = -d2n;
    }

    q0 += p0;

    float q1 = p1 + d1n * (float)(q0 - p0);

    if ( q1 > maxY ) q0 = p0 + (int)((maxY - p1) / (d1n ? d1n : 1)); else
    if ( q1 < minY ) q0 = p0 + (int)((minY - p1) / (d1n ? d1n : 1));

    if ( q0 == p0 )
        return false;

    float i2 = (float)p2;
    float i1 = (float)p1;

    if ( major == 0 )
    {
        for (int i0=p0;;)
        {
            if ( i0 == q0 )
                break;

            i0 += d0n; i1 += d1n; i2 += d2n;

            int i2_w = (int)i2 & coordMax;
            int i0_w = i0 & coordMax;
            if ( pMap[ (i2_w << sizL2) + i0_w ] > (int)i1 )
                return true;
        }
    }
    else
    {
        for (int i0=p0;;)
        {
            if ( i0 == q0 )
                break;

            i0 += d0n; i1 += d1n; i2 += d2n;

            int i2_w = (int)i2 & coordMax;
            int i0_w = i0 & coordMax;
            if ( pMap[ (i0_w << sizL2) + i2_w ] > (int)i1 )
                return true;
        }
    }

    return false;
}