STDMETHODIMP CTestViz::Render(TimedLevel *pLevels, HDC hdc, RECT *prc)
{
    // Fill background with black
    HBRUSH hNewBrush = ::CreateSolidBrush (0);
    HPEN hNewPen = ::CreatePen (PS_SOLID, 0, m_foreColor);
    HPEN hOldPen= static_cast<HPEN>(::SelectObject (hdc, hNewPen));
    HPEN hRedPen = ::CreatePen (PS_SOLID, 0, RED);
    HPEN hYellowPen = ::CreatePen (PS_SOLID, 0, YELLOW);
    HPEN hBluePen = ::CreatePen (PS_SOLID, 0, BLUE);

    ::FillRect( hdc, prc, hNewBrush );
    
    // draw using the current preset
    double pi = 3.1415926535;
    int height = prc->bottom - prc->top;
    int width = prc->right - prc->left;
    double hop, jump;
    if (width > SA_BUFFER_SIZE)
    {
        jump = static_cast <double> (width / SA_BUFFER_SIZE);
        hop = 1.0;
    }else{
        jump = 1.0;
        hop = static_cast <double> (SA_BUFFER_SIZE / width);
    }
    double vSize = height / 256.0f; // maximum value of signal
    // Walk through the frequencies until we run out of levels or drawing surface.
    int barWidth = 4;
    int shift = barWidth/2;
    int xoffset = width/2;
    int yoffset = height/2;
    int bassCut = width / 5;
    int midCut = width * 3 / 5;

    switch (m_nPreset)
    {
        case PRESET_SPIKES:
        {
            // This preset displays the energy in each frequency sample.
            // The color changes at the defined point of a shift from bass
            // to midrange, and again between midrange and treble.
            for (int x = 0; x < width; x += barWidth)
            {
                int index = static_cast <int> (x * hop);
                if (x < bassCut) ::SelectObject (hdc, hRedPen);
                else if (x > midCut) ::SelectObject (hdc, hYellowPen);
                else ::SelectObject (hdc, hBluePen);
                int y = static_cast<int>(vSize * pLevels->frequency [0][index] / 2);
                for (int z = 0; z < shift; z++)
                {
                    ::MoveToEx (hdc, z+xoffset+x-shift, prc->bottom-yoffset-y, NULL );  
                    ::LineTo (hdc, z+xoffset-x-shift, prc->bottom-yoffset+y);
                    ::MoveToEx (hdc, z+xoffset-x-shift, prc->bottom-yoffset-y, NULL );  
                    ::LineTo (hdc, z+xoffset+x-shift, prc->bottom-yoffset+y);
               }
            }
        }
        break;

        case PRESET_MOOD:
        {
            // Draw a radial bar for each adjusted sample
            // Set the color to the energy content of the frequencies by
            // setting the red value to the average of the values below the bass cut.
            // do the same for the midrange (blue) and treble (green).
            // X offset = cos angle * waveform height.
            // Y offset = sin angle * waveform height.
            // Angle increment = 2PI (radians in a circle) / width (number of samples).
            double angleInc = 2*pi/width;
            int j;
            int bass = 0;
            int mid = 0;
            int treble = 0;
            for (j = 0; j < SA_BUFFER_SIZE; ++j)
            {
                int fValue = pLevels->frequency [0][j];
                if (j < bassCut) bass += fValue;
                else if (j > midCut) treble += fValue;
                else mid += fValue;
            }
            int bassBoost = 4;
            int midBoost = 4;
            int trebleBoost = 4;
            bass /= bassCut;
            bass *= bassBoost;
            bass = min (bass, 255);
            mid /= midCut-bassCut;
            mid *= midBoost;
            mid = min (mid, 255);
            treble /= SA_BUFFER_SIZE-midCut;
            treble *= trebleBoost;
            treble = min (treble, 255);
            HPEN hfreqPen = ::CreatePen (PS_SOLID, 0, RGB (bass, treble, mid));
            ::SelectObject (hdc, hfreqPen);
            for (int i = 0; i < width; ++i)
            {
                double h = vSize * pLevels->waveform [0][static_cast <int> (i * hop)];
                int x = static_cast<int>(std::cos (i*angleInc) * h);
                int y = static_cast<int>(std::sin (i*angleInc) * h);
                y /= 2;
                x /= 2;
                ::MoveToEx (hdc, prc->left + xoffset, prc->bottom - yoffset, NULL );  
                ::LineTo (hdc, prc->left+xoffset+x, prc->bottom-yoffset-y);
            }
            if (hfreqPen) ::DeleteObject (hfreqPen);
        }
        break;

        case PRESET_SCOPE:
        {
            // Walk through the waveform data until we run out of samples or drawing surface.
            int y = static_cast<int>(((prc->bottom - prc->top)/256.0f) * pLevels->waveform[0][0]);
            ::MoveToEx( hdc, prc->left, y, NULL );  
            for (int x = prc->left; x < prc->right && x < (SA_BUFFER_SIZE-1); ++x)
            {
                y = static_cast<int>(((prc->bottom - prc->top)/256.0f) * pLevels->waveform[0][x - (prc->left - 1)]);
                ::LineTo(hdc, x, y); 
            }
        }
        break;
    }
        
    if (hNewBrush)
    {
        ::DeleteObject( hNewBrush );
    }

    if (hNewPen)
    {
        ::SelectObject( hdc, hOldPen );
        ::DeleteObject( hNewPen );
    }
    if (hRedPen) ::DeleteObject (hRedPen);
    if (hYellowPen) ::DeleteObject (hYellowPen);
    if (hBluePen) ::DeleteObject (hBluePen);
    
    return S_OK;
}