Quote Originally Posted by Potato_Priest View Post
I'm not sure that light in D&D 5e is the same thing as light in our own universe, and probably doesn't count as a "thing".
I can get behind this.

The following is an argument that could be based off assuming that light in D&D and light in the real world are the same thing.

Spoiler: Realistic light and illusions
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If light can't reflect off an illusion, how would you be able to see it?

If an illusion is able to interact with light then illusions would cast shadows and be able to have other objects project shadows onto them, and an illusion could reflect light, making it visible.

If an illusion totally didn't interact with light, it would be invisible unless it was a mental projection, because ambient light would pass through it rather than reflecting off of it.

If an illusion doesn't interact with light at all, and is just a mental projection, then you would be able to see it in a completely dark room (and maybe even with your eyes closed), which doesn't seem right, and could also lead to ridiculous munchkinery where people could see illusions regardless of physical barriers (IE using it as a signal in darkness or a fog cloud)


In essence, because there aren't real illusion spells, it is impossible to predict how real world light would interact with them. Using the real-world definition of light as an "object" doesn't necessarily apply to D&D.
This is true, but we do have such a thing as 3D holograms. These are how I tend to think of illusions as working.