The Physics of Darkness (was Shadows of Illumination)

[Jhyrryl]

Since a darkness spell radiates darkness, does it throw "shadows" when obstructed by objects? Or is the darkness considered to spread like a fireball? One or the other is implied by the fact that a darkness radiating object can be suppressed by enclosing it in a light-proof container.

Someone outside the darkness should then be able to detect the presence of said intervening objects, even in the case of a spread, because the need to wrap around the intervening object would create a deformity in the sphere's shape. The bigger the object, the bigger the deformity. And in the case of "shadows" being thrown, someone within the darkness should be able to easily find their way out. They could even "shade" their eyes and be able to find their way in the correct direction of the radiating source.

Adventure hook: "Last night, an area of deeper darkness was cast at the center of every intersection in the market district!" At least once a week thereafter, the event repeats itself, and the PCs are hired to track down the cause. Ah the joys of "at-will" abilities.

 

[Maitre Du Donjon]

Darkness isnt "Anti-light". The description of the spell is pretty clear IMO, in the sense that if you don't want an object radiating darkness in a 20' radius, you have to place it "inside or under a lightproof covering. [the effects] are blocked until the covering is removed.

Maitre D

 

[Jhyrryl]

So many side effects...

Darkness isnt "Anti-light".

Isn't it? What is it then? Something is being radiated. Something that "counters or dispels any light spell of equal or lower level". Sounds like anti-light to me.

The description of the spell is pretty clear IMO, in the sense that if you don't want an object radiating darkness in a 20' radius, you have to place it "inside or under a lightproof covering. [the effects] are blocked until the covering is removed.

The spell description is pretty clear, but the spell information is incomplete. The spell description clearly states that it "causes the object to radiate darkness out to a 20-foot radius." The problem is that the designers forgot to include an Area entry in the spell, which I'd expect to be similar to the Area entry for silence.

Without the area entry, we do not know what kind of radiation darkness falls under. My bet is that darkness is an emanation (see PHB Chapter 10: Casting a Spell; Aiming a Spell). An emanation is a burst with a duration, so if darkness is an emanation, it would throw "shadows" as I described. If it's not an emanation then it would most likely be something that is not defined in the rules: a spread with a duration, which would exhibit the properties I described previously.

I note that daylight also has no Area entry, probably because the designers took for granted the behavior of light as so intuitive, that they either consciously felt it didn't require an explanation, or subconsciously forgot that fantasy game mechanics may require such a description. The darkness spell was probably then written as a mirror to daylight, and the omission of mechanically describing darkness energy's behavior, overlooked.

In the following, point A is a pebble with darkness cast on it, B is the location of your character, the brown area is a 5-foot thick, 30-foot high, solid-stone wall, and the dashed blue line is a similarly tall wall of force.

Image 1 is a case-study for why darkness must be a radiating energy that throws a "shadow". If the darkness energy could penetrate through the material of the wall to enshroud your character at B, then it should be able to penetrate the same material, even if it completely enclosed the source.

Image 2 demonstrates the behavior of darkness as an emanation. The wall blocks the path of the energy, only allowing totally unobstructed energy past, thereby allowing your character at B to see normally.

Image 3 demonstrates the behavior of darkness as the undefined "spread with a duration". The wall blocks the path of the energy, but it wraps around the obstruction to a distance of 20-feet.

Image 4 begs the question, "Are transparent objects also transparent to magical darkness?" IMO they are. But a strong argument can probably be made the other way.