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 Post subject: line 0 sprite throw away
PostPosted: Tue Dec 21, 2004 8:38 pm 
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What does NintTech doc means whit Line 0: Throw Away All Sprite Data?

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PostPosted: Thu Dec 23, 2004 5:15 pm 
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I'm guessing that the author of the document means that there must be a garbage line (scanline #0) so that the PPU can evaluate the sprite positions for the next scanline. Read Brad Taylor's doc for a better explanation.

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PostPosted: Thu Dec 23, 2004 6:15 pm 
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If you set a sprite's Y coordinate to 0, it'll be drawn on lines 1 through 8 or 1 through 16 depending on the sprite height switch. So I thought the garbage line for computing sprite priority was the first line of the actual screen, because a sprite can't start on line 0, right? Or does the PPU take two lines to compute sprite priority, doing the first half on line y-1, the second half on line y, and actually displaying the sprite on line y+1?


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PostPosted: Thu Dec 23, 2004 10:49 pm 
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The reason for the garbage scanline is NOT to detect sprites for the first visible scanline (since there can never be any sprites there anways) - its sole purpose is to initialize the BACKGROUND render pipeline (the last 2 BG tile fetches).

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PostPosted: Thu Dec 23, 2004 10:58 pm 
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Sixteen pixels, all well within the overscan on NTSC and barely noticeable on PAL, so who gives a sh**, turning the screen on late means MORE VBLANK TIME FOR MEEEEEE!!!!!111

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PostPosted: Fri Dec 24, 2004 10:54 am 
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Quietust wrote:
The reason for the garbage scanline is NOT to detect sprites for the first visible scanline (since there can never be any sprites there anways) - its sole purpose is to initialize the BACKGROUND render pipeline (the last 2 BG tile fetches).


But that has nothing to do with "sprite data throwaway". Whoever wrote that must have been high or something.

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PostPosted: Fri Dec 24, 2004 1:08 pm 
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Hyde wrote:
But that has nothing to do with "sprite data throwaway". Whoever wrote that must have been high or something.

That, or he simply copied the data he saw in Brad Taylor's document and assumed it was correct.

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