udmf_zdoom.txt wrote:sector
{
alphafloor = <float>; // translucency of floor plane (only has meaning with Sector_SetPortal) Default is 1.0.
alphaceiling = <float>; // translucency of ceiling plane (only has meaning with Sector_SetPortal) Default is 1.0.
...
portal_ceil_alpha = <float> // translucency of ceiling portal (default is 0 (not visible))
portal_floor_alpha = <float> // translucency of floor portal (default is 0 (not visible))
}
Judging by the source, these 2 pairs of properties do exactly the same thing.