As explained in PLAYERS HANDBOOK, infravision is the ability to see light waves in the infrared spectrum.
Characters and various creatures with infravisual capability out to 60' (standard) are basically picking up radiation from their surroundings.
Therefore they note differences in thermal radiation, hot or cold.
They do not "see" things which are the same temperature as their surroundings.
Thus, a room in a dungeon might look completely blank, as walls, floor, ceiling, and possibly even some
wooden furniture within are all of the same temperature. Openings in the
walls should show up rather plainly, as space anywhere else will, and if
you are generous, you can allow different substances to radiate differently
even if at the same temperature, i.e. the wood in the example above
would be discernible if care was used in scanning the roam infravisually.
Note that air currents might show as cold or warm layers. Except where
very warm or very cold objects are concerned, vision of this sort is roughly
equal to human norm on a dark and cloudy night at best. Note also that
monsters of a very cold or very warm sort (such as a human) can be
tracked infravisually by their footprints. Such tracking must occur within 2
rounds of their passing, or the temperature difference where they had
trodden will dissipate.
Light sources which give off heat also absolutely prevent
from functioning within their sphere of illumination. (Explain this as
the effect of trying to see into the dark when the observer is in a brightly lit
area.) It requires not less than two segments to accustom the eyes to infravision
after use of normal vision.
Creatures with infravisual capability of unusual nature,
such as those
which see infrovisually to 90', are actually emitting infrared radiation from
their eyes and seeing what is within this visual range by receiving the
reflected radiation. Such creatures can easily distinguish floor, ceiling,
wall, and other areas, as well as furnishings within an area.
The eyes of all such creatures will appear as very brightly glowing red
when observed by any other creature with standard infravision.
Most monsters inhabiting underground areas will have this form of infravision.
lnfravision outdoors enables the individual to see figures
which are warm or cold at 100' to 300',
depending on temperature extremes. Vision is otherwise equal to a bright, starry night, with full moonlight.
Ultravision is the ability to see radiation above violet
in the normal visible spectrum.
Unless this ability is of highly unusual nature,
so as to be able to see far into this spectrum,
ultravision will not be useful underground (where radiation is screened out) without some source of ultravisual emanation.
Magic weapons which shed illumination spoil ultravisual capability,
just as heat does infravision.
As noted in PLAYERS HANDBOOK,
ultravision enables the viewer to see outdoors at night as if he or she were in twilight,
so vision extends clearly for about 100 yards, dimly to about 300.
On particularly cloudy nights, ultravisual capability is reduced to about half normal,
i.e. clear sight to 50 yards, dim to 150 yards.