I noticed a question on the PPU Rendering page on the wiki, back from 2015, asking what the fetches on the prerender scanline are, since it makes the same fetches a visible scanline would.
My guess is that the fetches depend on what the current value of the PPU's V register is at the time the prerender scanline starts. So for example, if the game's vblank routine finishes by setting the scroll registers, V will be the same as T, and scanline -1 will make the same fetches scanline 0 will. If the PPU isn't touched at all, then scanline -1 will make fetches like it's rendering a hypothetical "scanline 240" (i.e., where V left off when the previous frame finished).
Could anyone confirm this before I add anything to the wiki?
What are the fetches on the pre-render scanline?
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Re: What are the fetches on the pre-render scanline?
It does just start rendering with the contents of V before it reloads V from T.
This can be verified by looking at my hardware capture of the SMB3 title in this post
This can be verified by looking at my hardware capture of the SMB3 title in this post
Re: What are the fetches on the pre-render scanline?
Thank you, I've added this and the sprite fetches to the wiki.
As a sidebar, it's mind blowing what a difference 12 years of knowledge makes; back then, I'd have no clue, but today, it was just "oh yeah it's probably just whatever V's set to, easy peasy". (Still wanted to be sure though)
As a sidebar, it's mind blowing what a difference 12 years of knowledge makes; back then, I'd have no clue, but today, it was just "oh yeah it's probably just whatever V's set to, easy peasy". (Still wanted to be sure though)