can light pass thru illusionary wall?

[azmodean]

I agree with radferth, you can't use physics to try to interpret the rules (unless you are house-ruling, which is a different subject entirely).

A light emmiting object provides light in a certain radius, depending on the object. An illusion effect can alter what is percieved to exist within it's area of effect. What the illusion cannot do is alter what is percieved outside it's area of effect, such as by blocking light. The source of the light will not be visible, but the illusion is not capable of blocking the light effect.

Also there is this, from the description of the Invisibility spell:

Light, however, never becomes invisible, although a source of light can become so (thus, the effect is that of a light with no visible source)

I think it is pretty resonable to conclude that if invisibility is unable to block the light, then an illusion spell would also be unable to do so (outside of its area of effect anyway)

 

[DarkMaster]

I don't understand your logic. Invisibility doesn't stop light because all it does is prevent a physical body from interacting with light. The body becomes unable to block the light, therefore invisible because no light reflects on it. Therefore any light produced by the body is obviously not blocked. An illusion on the other hands play with the light in such a way that it makes you beleive something is present when it's not. Therefore the illusionary wall distorts all lights passing through it on all sides.

Allowing light to go through illusion would weaken them even more and it's not like illusion are overpowered in the game. Illusion would become really easy to detect, since they don't block light they don't create any shadow. Illusion would only become usefull against creature using darkvision and that's very boring.

 

[ThirdWizard]

If light goes through an illusionary wall because it doesn't block the effect of the illumination, then an invisible wall should block the radius of the light. So invisible creatures would cast shadows.

By the way this is not my interprietation of how it actually works, its an extrapolation of what should happen if illusionary walls don't block light effects.

 

[Whimsical]

Just don't forget to "render" the illusion's shadow when you project your illusion. But I will go with the "Illusions are opaque, but doesn't block light" paradox when I run games. It does seem to fit the existing rules the best. Very wierd, but I'll see what I can do with that.

 

[Cheiromancer]

I will go with the "Illusions are opaque, but doesn't block light" paradox when I run games. It does seem to fit the existing rules the best. Very wierd, but I'll see what I can do with that.

Think of it like this: when light travels through an illusion, it is changed so that it cannot be absorbed without first being reflected. If it would be absorbed (by striking a dark surface, say) it just disappears.

This allows objects to be opaque without blocking light or casting shadows.