texel pipeline

/* select zero/other for RGB */
if (!TEXMODE_TC_ZERO_OTHER(TEXMODE))
{
    tr = COTHER.rgb.r;
    tg = COTHER.rgb.g;
    tb = COTHER.rgb.b;
}
else
    tr = tg = tb = 0;

/* select zero/other for alpha */
if (!TEXMODE_TCA_ZERO_OTHER(TEXMODE))
    ta = COTHER.rgb.a;
else
    ta = 0;

/* potentially subtract c_local */
if (TEXMODE_TC_SUB_CLOCAL(TEXMODE))
{
    tr -= c_local.rgb.r;
    tg -= c_local.rgb.g;
    tb -= c_local.rgb.b;
}
if (TEXMODE_TCA_SUB_CLOCAL(TEXMODE))
    ta -= c_local.rgb.a;

/* blend RGB */
switch (TEXMODE_TC_MSELECT(TEXMODE))
{
default:/* reserved */
case 0:/* zero */
    blendr = blendg = blendb = 0;
    break;

case 1:/* c_local */
    blendr = c_local.rgb.r;
    blendg = c_local.rgb.g;
    blendb = c_local.rgb.b;
    break;

case 2:/* a_other */
    blendr = blendg = blendb = COTHER.rgb.a;
    break;

case 3:/* a_local */
    blendr = blendg = blendb = c_local.rgb.a;
    break;

case 4:/* LOD (detail factor) */
    if ((TT)->detailbias <= lod)
        blendr = blendg = blendb = 0;
    else
    {
        blendr = ((((TT)->detailbias - lod) << (TT)->detailscale) >> 8);
        if (blendr > (TT)->detailmax)
            blendr = (TT)->detailmax;
        blendg = blendb = blendr;
    }
    break;

case 5:/* LOD fraction */
    blendr = blendg = blendb = lod & 0xff;
    break;
}

/* blend alpha */
switch (TEXMODE_TCA_MSELECT(TEXMODE))
{
default:/* reserved */
case 0:/* zero */
    blenda = 0;
    break;

case 1:/* c_local */
    blenda = c_local.rgb.a;
    break;

case 2:/* a_other */
    blenda = COTHER.rgb.a;
    break;

case 3:/* a_local */
    blenda = c_local.rgb.a;
    break;

case 4:/* LOD (detail factor) */
    if ((TT)->detailbias <= lod)
        blenda = 0;
    else
    {
        blenda = ((((TT)->detailbias - lod) << (TT)->detailscale) >> 8);
        if (blenda > (TT)->detailmax)
            blenda = (TT)->detailmax;
    }
    break;

case 5:/* LOD fraction */
    blenda = lod & 0xff;
    break;
}

/* reverse the RGB blend */
if (!TEXMODE_TC_REVERSE_BLEND(TEXMODE))
{
    blendr ^= 0xff;
    blendg ^= 0xff;
    blendb ^= 0xff;
}

/* reverse the alpha blend */
if (!TEXMODE_TCA_REVERSE_BLEND(TEXMODE))
    blenda ^= 0xff;

/* do the blend */
tr = (tr * (blendr + 1)) >> 8;
tg = (tg * (blendg + 1)) >> 8;
tb = (tb * (blendb + 1)) >> 8;
ta = (ta * (blenda + 1)) >> 8;

/* add clocal or alocal to RGB */
switch (TEXMODE_TC_ADD_ACLOCAL(TEXMODE))
{
case 3:/* reserved */
case 0:/* nothing */
    break;

case 1:/* add c_local */
    tr += c_local.rgb.r;
    tg += c_local.rgb.g;
    tb += c_local.rgb.b;
    break;

case 2:/* add_alocal */
    tr += c_local.rgb.a;
    tg += c_local.rgb.a;
    tb += c_local.rgb.a;
    break;
}

/* add clocal or alocal to alpha */
if (TEXMODE_TCA_ADD_ACLOCAL(TEXMODE))
    ta += c_local.rgb.a;

/* clamp */
RESULT.rgb.r = (tr < 0) ? 0 : (tr > 0xff) ? 0xff : tr;
RESULT.rgb.g = (tg < 0) ? 0 : (tg > 0xff) ? 0xff : tg;
RESULT.rgb.b = (tb < 0) ? 0 : (tb > 0xff) ? 0xff : tb;
RESULT.rgb.a = (ta < 0) ? 0 : (ta > 0xff) ? 0xff : ta;

/* invert */
if (TEXMODE_TC_INVERT_OUTPUT(TEXMODE))
    RESULT.u ^= 0x00ffffff;
if (TEXMODE_TCA_INVERT_OUTPUT(TEXMODE))
    RESULT.rgb.a ^= 0xff;