Insight on Light Radius

[Danest]

Haunted House and Adventure both used a light radius around the player when in a maze -- you could see what was inside of your light radius, like walls of a maze, but not beyond it. Does anyone have any insight on how they did that, especially with so little ram? I mean, it's not a bullet, it's probably not a sprite... I can imagine it wouldn't be hard on a modern computer's resources but I really don't know what they did on an atari to do that. In fact I find it amazing that adventure (and certain other more-advanced-than-usual-games) were created at all on an Atari at all.

[+SpiceWare]

You can use Stella to figure out things like this. It has a handy Debug Color mode that makes it so you can see all the objects. The debugger also has a TIA tab that shows the state of all the objects.

 

Screenshot of Adventure:

 

Screenshot of Adventure using Debug Color mode. Toggle this setting by hitting the keys COMMAND-COMMA on a Mac or ALT-COMMA on other systems.

 

This are the object colors in Debug Color Mode.

 

Stella debugger showing showing 4x player and Playfield Priority. To enter the debugger hit ` (the key to the left of the 1 and just below ESCAPE). Hit it again to exit the debugger.

 

"player" is what sprites were called when the Atari was designed, so for Adventure the light radius is a sprite set to 4x size. The playfield is also set to have priority over the other objects so that they get drawn behind it. Finally the play field is colored the same as the background.

 

 

 

Now try this with Haunted House and tell me what you found

[Nukey Shay]

Correct. In both games, bit2 is set in CTRLPF to make sprites be hidden under playfield pixels...and the "light" is drawn at quad width using GRP1. That sprite and it's missile have lowest priority (other than the background color) when CTRLPF = %-----1--, so Adventure's ball sprite or Haunted House's GRP0 eyes are visible above the sprite that the light is drawn with.

[The Eyeball Mural]

Which explains why flicker is encountered in the dot room of the grey dungeon (black castle maze) in Adventure when only one "nominal" object is in the room: nominal object (e.g. sword) + dot + torchlight = flicker threshold reached?