POLYTYPE_PTEX (3) - Linux Man Pages
POLYTYPE_PTEX: Polygon rendering mode type Allegro game programming library.
POLYTYPE_PTEX - Polygon rendering mode type Allegro game programming library.
A perspective-correct texture mapped polygon. This uses the `z' value from
the vertex structure as well as the u/v coordinates, so textures are
displayed correctly regardless of the angle they are viewed from. Because
it involves division calculations in the inner texture mapping loop, this
mode is a lot slower than POLYTYPE_ATEX, and it uses floating point so it
will be very slow on anything less than a Pentium (even with an FPU, a 486
can't overlap floating point division with other integer operations like
the Pentium can).