I have a 2D array that deals with lighting in my game, and I'd like to be able to just create a "seed" light and have the dropoff automatically happen, so I can have dynamic lighting and such. Like so:
Seed lights:
0,0,0,0,0,0,0,0,0,0
0,4,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,0
0,2,0,0,0,0,0,0,8,0
0,0,0,0,0,0,0,0,0,0
With dropoff:
1,2,1,0,0,0,0,0,1,0
2,4,2,1,0,0,0,1,2,1
1,2,1,0,0,0,1,2,4,2
1,2,1,0,0,1,2,4,8,4
0,1,0,0,0,0,1,2,4,2
But I'm not sure how to do it in a way that wouldn't slow down the game too much if it's calculated often. Does anyone have any advice about how I should do this? I need to do it once every second, at least, since there are objects that move around that give off light, and daylight.
Presumably, you're iterating through this array to render the lighting.
My immediate thought is that the light reaching a particular coordinate is just a function of the coordinate's distance from the source and the total brightness of the source. Instead of maintaining an array, I would keep a list of light sources and their coordinates, then calculate the total light hitting a given x/y coordinate. Let's say (x1,y1) is your light source and (x2,y2) is the coordinate you're testing.
For a circle, it's just sqrt((x2 - x1)^2 + (y2 - y1)^2); repeat for all sources in the list, summing the results. Total value is the total light hitting x2,y2.
Yours seem like they could be asymptotes, but I can't really tell. Off the top of my head, if you want something asymptotic, it's more like: ((c / |(x2 - x1)|) + (c / |(y2 - y1)|)) / 2; where || denotes absolute value and c is total brightness.
Does that help? I couldn't tell if your question was asking about formulas or array optimisation. If it's the latter, I don't think you need to store things in arrays, but I guess more info would help clarify.