I’m in a Dungeons & Dragons game where our GM (game master) is fond of saying, “this is not a [fill in the blank] simulator.” Recently, the question of how darkvision works in the game came up, so I’ve been inspired to use my 3D rendering skills to examine the issue.
This is a Darkvision Simulator
(You may want to click on the images to see the full size versions and see the details I’ll be talking about.)
I’m starting with this scene underground. I’m holding a torch to my left and I have normal vision. Pete is just 10 feet in front of me and I can see him quite clearly. His companion Laura is just 30 feet away from me and down a few steps. That puts her just on the border between the torches bright light and dim light according to the rules, and she is also quite visible. In the dim light, 50 feet away, you can probably see their halfling friend, Gaby (if you look at the fulls size picture and have a computer display with good luminosity). Beyond that, you can’t see much.
NOTE: None of these pictures are using a reality based lighting. In order to have light behave the way the rules call for, I decided to use point lights with linear falloff rather than real world geometric falloff. The light intensity is set to reach 0 at 60 feet.
This is the same scene, but now I, the viewer, have darkvision of the 60 foot range variety. Everything looks brighter, so I can see more detail, but I can’t see any further than I could before. Darkvision is not color vision, so while the color I can see from the torch light is not removed, no additional color is added; just brightness. It makes the people look pale.
NOTE: I did this by adding another light, similar to the torch, but originating directly from my point of view, casting no shadows, and then used the rendered image to modify the luminosity of the first image, but not add color.
Here I’ve bumped the darkvision up to a 90 foot range. Now we can see the monster lurking in the dark just beyond our torch light. That creature is 70 feet away from us, and we can’t see any color in it. The far end of the room is just the edge of our darkvision range, so we can start to see it, but can’t make out much detail.
Bumping the darkvision up to a 120 foot range, we can finally see detail at the end of the room, one of those details being Juanita. Looks like she’s preparing to cast a spell at that monster. Again, no color at that distance.
Now that we have 120 foot darkvision, maybe we should just snuff out the torch and see what happens.
Without the torch, we lose all of the color. Pete and Laura have lost the extra brightness, but we can still see them clearly and in detail.
NOTE: Because of the angle of the torch, and some other factors, we didn’t have much in the way of shadows in the first place, but it’s worth saying that darkvision doesn’t provide any shadows of its own. That can leave the scene looking a bit flat.
That could have been the end of it, but then I thought, “What if there was a light source at the end of this cavern hall?”
I’ve returned to normal vision, relit my torch, and lit a torch on the wall at the opposite end of the chamber. Now we can see everyone in the room. Juanita and the monster, because of their positions relative to the distant torch, appear mostly as silhouettes. Everything has color now, including the ceiling which is now very visible.
Turning on the darkvision 60 feet adds some detail to nearby objects, but does nothing for the distant objects.
Extending our darkvision to 90 feet, the monster is no longer a silhouette.
Extending our darkvision to 120 feet, we can see a little detail in Juanita.
Now suppose we are sneaking, and have our own torch extinguished, but the distant torch is still lit.
Though I am in darkness, I can see the far end of the room clearly. Juanita and the monster are still looking like silhouettes because of their positioning, but what about these other people. Pete is certainly in darkness as much as I am, but he and Laura and Gaby are visible to me as silhouettes because they are blocking my view of the lit areas.
Bringing back the 60 foot darkvision, we get the odd effect of nearby objects being grey while distant objects are in color.
There’s nothing unexpected as we ramp up the darkvision to 90 and then 120 feet. More light, but not more color.
In conclusion, this is just one person’s way of looking at darkvision; a blend between how light really works, and how D&D 5.0 tells us it works. I think it gives us fun and somewhat believable fantasy.
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