Function pvDecompress

ogsr_engine/xrCore/_compressed_normal.cpp:103–139

}

void pvDecompress(Fvector& vec, u16 mVec)
{
    // if we do a straightforward backward transform
    // we will get points on the plane X0,Y0,Z0
    // however we need points on a sphere that goes through these points.
    // therefore we need to adjust x,y,z so that x^2+y^2+z^2=1

    // by normalizing the vector3. We have already precalculated the amount
    // by which we need to scale, so all we do is a table lookup and a
    // multiplication

    // get the x and y bits
    int xbits = ((mVec & pvTOP_MASK) >> 7);
    int ybits = (mVec & pvBOTTOM_MASK);

    // map the numbers back to the triangle (0,0)-(0,126)-(126,0)
    if ((xbits + ybits) >= 127)
    {
        xbits = 127 - xbits;
        ybits = 127 - ybits;
    }

    // do the inverse transform and normalization
    // costs 3 extra multiplies and 2 subtracts. No big deal.
    float uvadj = pvUVAdjustment[mVec & ~pvSIGN_MASK];
    vec.x = uvadj * float(xbits);
    vec.y = uvadj * float(ybits);
    vec.z = uvadj * float(126 - xbits - ybits);

    // set all the sign bits
    if (mVec & pvXSIGN_MASK)
        set_negative(vec.x);
    if (mVec & pvYSIGN_MASK)
        set_negative(vec.y);
    if (mVec & pvZSIGN_MASK)
        set_negative(vec.z);
}