I read
http://www1.cs.columbia.edu/~sedwards/p ... 1989tv.pdf.
It says in P.4(row 43)
Quote:
An assumption is made here that the display area or screen has the width of 256 dots in the horizontal direction and the height of 240 dots in the vertical direction and a character constituting a motion picture or still picture is defined by a matrix of 8 dots by 8 dots. It is also assumed that the max. number of motion pictures to be displayed on a single horizontal line is eight and thus 64 motion pictures may be displayed on the screen at maximum at the same time.
Please tell me how to derive "64" from "number of motion pictures to be displayed on a single horizontal line is eight".
There can be 8 sprites horizontally aligned. There can be more sprites above and below those 8 sprites, for a total of 64 per scene.
Sir tepples.Thanks always.
I am confused.
30 tiles can align vertically , so I think 8 titles per same line lead 240 sprites at most.
Simply put.
At most only 64 sprites can be defined on the whole screen.
You can actually even make all 64 sprites occupy the same line, but only at most 8 of them could be displayed on that line at the same time.
Those are 2 independent limitations. There's memory for defining 64 sprites, and the PPU is able to find and draw at most 8 per scanline, but there's no direct correlation between those 2 facts. They probably shouldn't have used the word "thus" in that document.
So the restriction, 8 sprites par same line has nothing to do with 64 sprites,dose it?
Thank you everyone.
Well, I wouldn't say NOTHING, since both limitations exist because of time constraints... Each scanline takes a little bit of time, and that time has to be spent scanning all the sprites looking for the ones that are in range, and fetching the data and the patterns of the ones that are. If more sprites have to be scanned, there'll be less time to actually draw the ones that are found. So 64 and 8 probably seemed like a good balance to the PPU engineers, also considering the amount of memory that had to be built into the chip to hold the OAM and the in range sprites.
I'm sorry I said too much.
My understanding has developed very much.
Everybody Awesome!