The issue of a light radius in Diablo III came up back in 2008, shortly after the game’s debut, as part of the whole Art Controversy. Fans accustomed to the 2D visuals of D1/D2 wondered why there was no such circle of illumination around the heroes in the dungeons. Jay Wilson made some comments about that back in the day, asserting that it just didn’t work in the 3D engine and with the atmospheric lightning in their dungeons (See the [/wiki]light radius[/wiki] article in the DiabloWiki for quotes.) and Bashiok returned to the topic today.
We try to keep the visuals changing from area to area, even within the same Act. It keeps the game interesting, and is its own reward when a player makes it to that next area and the color palette does a complete shift and the area changes from a dark and foggy moor with blues and greens to a starkly clear dungeon with reds and purples. It’s a very powerful way of reinforcing progression. Most people don’t think about it as a gameplay mechanic, but it absolutely is.
As Bashiok says there at the end, it’s an important gameplay mechanic. He clearly means that in the Diablo III sense of what you can see, but the real import of your light radius in D1 and D2 was not what you could see, what what could see you.
In the previous games in the Diablo series, your character’s light radius determined how close you could get to monsters before they “saw” you; before they reacted to you. That wasn’t such a huge factor in D2, but it was a big deal in D1, where warriors often chose to minimize their light radius in order to play in stealth mode. (Especially with the aid of Infravision.). It was very useful in D1 to have fewer monsters at a time aware of you, so you could kill them one or two at a time (instead of 4 or 5 at a time, which meant retreat in D1), and especially so ranged attackers wouldn’t start firing at you while you were chopping up the melee enemies.
The real question for D3 then, is what determines how and when the monsters see your character? If there’s no light radius, is there no way to play in stealth mode? Do characters become more or less visible to monsters depending on their Clvl? Equipment? Anything? Do monsters react to spells or projectiles? If you drop a Blizzard at the edge of the screen, will monsters under it stand there and freeze if they’re beyond their visual range? Or will they know who cast it and attack? How about the other monsters near enough to “see” the spell attack, but not the character who cast it?
One of the theories for Inferno difficulty is that monsters will get better AI as well as more hit points, higher damage, better resistances and defense, etc. If the game code allows the developers to improve the aggressiveness, vision range, reaction time, etc for the monsters, that could make a noticeable difference in how the game plays at the highest difficulty level.