Method GetMipLevel

cmp_framework/common/cmp_mips.cpp:810–874

}

CMP_MipLevel* CMP_CMIPS::GetMipLevel(const CMP_MipSet* pMipSet, int nMipLevel, int nFaceOrSlice)
{
    if (!pMipSet)
    {
        assert(pMipSet);
        return NULL;
    }

    if (!pMipSet->m_pMipLevelTable)
    {
        return NULL;
    }

    if (nMipLevel > MAX_MIPLEVEL_SUPPORTED)
    {
        return NULL;
    }

    if (nMipLevel > pMipSet->m_nMaxMipLevels)
    {
        assert(nMipLevel <= pMipSet->m_nMaxMipLevels);
        return NULL;
    }
    if (nFaceOrSlice < 0)
    {
        return NULL;  //not an error, indicates requested face doesn't exist
    }
    int nDepth = pMipSet->m_nDepth, index = 0, whichMipLevel = 0;

    switch (pMipSet->m_TextureType)
    {
    case TT_1D:
    case TT_2D:
        if (nFaceOrSlice != 0)
        {
            return NULL;
        }
        return (pMipSet->m_pMipLevelTable)[nMipLevel];
    case TT_CubeMap:
        if (nFaceOrSlice > 6)
        {  //cubemap have at most 6 faces
            assert(nFaceOrSlice > 6);
            return NULL;
        }
        return (pMipSet->m_pMipLevelTable)[nMipLevel * nDepth + nFaceOrSlice];
    case TT_VolumeTexture:
        while (whichMipLevel <= nMipLevel)
        {
            if (whichMipLevel == nMipLevel)
            {
                return (pMipSet->m_pMipLevelTable)[index + nFaceOrSlice];
            }
            else
            {
                index += nDepth;
                whichMipLevel++;
                nDepth = nDepth > 1 ? nDepth >> 1 : 1;
            }