EFB issues

[gunmoule]

Hi,

Trying various configurations to play ZTP I noticed an issue with EFB disabled. The upper left corner of the screen freeze to the frame being displayed as the EFB turned off (pic attached).

So the question. Is it a normal/common issue or is it specific to some games/Dolphin-emu revs/computer ??

And by the way if someone can explain what is EFB and what's the difference copying that stuff to ram/ GL texture ?

[Glurion]

Hey, it stands for Extended Framebuffer, it's basically the way a gamecube renders graphics or something along those lines, I'm not to sure but you can see it here.

and it also happens to me with twilight and from what i can make out from the documentation its because when the EFB is disabled the graphics cannot be rendered correctly.

I'm not sure if this is correct how i explained it, feel free to correct me lol

[gunmoule]

Thanks mate, sounds like a good answer to me. But the new question is, if EFB is the only way to render 3D graphix how do you explain ZTP is still running with EFB disabled excepting in that ugly square on the upper left corner.

PS: Can't figure out how I missed the page about EFB. Thx Glurion.

Oh, and cheers to the dolphin team, since the last build there is no longer TLB errors with ZTP NTSC.

[Glurion]

I think it's because it is still rendering the graphics but because there's nowhere for the rendered graphics to be stored ready for output, so it tries to render them in real time, and it unfortunately cannot do this quick enough so the last part of the screen is left unrendered.

[gunmoule]

Fixed as Rev 2972, ZTP runs well (with some graphical errors in water areas) with EFB disabled, and it gives great FPS improvement in large areas!

So Glurion I think we are wrong on what is EFB or how it runs on ZTP.

Edit: I came to the conclusion that it is an incompatibility with ZTP bloom hack that cause this stuff with EFB disabled

[Glurion]

No i think were right on some level but it's also cause dolphin gets better over time

[Unknownforce]

EFB is a way to render certain graphics... like the pause screen in some games, where the game gets "screenshotted" and rendered in the background of the menus.. or like in Metroid Prime when you switch on the scanner, inside that box is the EFB graphics.

So disabling it would turn those off, but not all graphics. Most EFB's you will notice are kind of "blurred" images. Some games use it more, others not so much. But disabling it will remove any textures that use it as it's rendering engine. So you might get the speed improvement, but you'll also be removing the ability to display anything through EFB.

[hakunushi]

EFB is a stack, where it saves pre-rendered frames, will b used to pre-render effects like fog and some animations, also used to render far views, in the past lack of efb caused games to have a limited distance view, the machines/consoles wouldnt have enough memory to render too much landscape, get mario kart wii and disable the efb, u will notice that far objects will get rendering problems.

efb is also used to many other things, o mario strickers wii u may be presented by a black screen sometimes, u see no pre-rendered frames, as u can see on a real gc u got 2mb of fast EDRAM, this is expensive uber fast RAM, u can notice that among all 128 bit consoles GC got the best drawing distance capabilities. well i dont know if pcs video cards has these features, i guess our common RAM memory is used then thats why it represents slow downs, maybe, i wonder.

[gunmoule]

Thanks hakunushi,

Further investigations showed that in ZTP (GC NTSC) EFB is used to render some fog effects (on top of fires and torches), all water reflection rendering, map transparency and some very uncommon stuff. Maybe its used for a layer of the twillight realm fog.

So ingame disabling EFB will cause 3 major issues:

-no map displayed
-no water reflection
-conflict between "ZTP Bloom Hack" and "EFB Off"

On the other hand and I cant figure out why, Midna's shadow will be displayed correctly in light realm. (with EFB on you just see a glowin light)

[thegamefreak0134]

EFB stands for "External Framebuffer".

The important part there is Framebuffer. In a nutshell, the GameCube (And Wii, of course) is capable of rendering the current scene directly to memory, where the game can pick it up and use it as a texture. So, by lagging behind the graphics one frame (which certainly isn't noticable) the game can do post-processing on the previously rendered frame and add something nifty in. In Zelda, a bloom effect is added to the scene, which gives the whole game that beautiful glowy look. On top of this, the game can certainly do some basic software rendering on the extra layer, which is why sometimes the graphics disappear with the EFB disabled.

When EFB has been running and stops running suddenly, what's left in that memory location is the *last frame that was rendered*. This is why it's "freezing" the corner of the screen there, because when you turn the EFB off it doesn't properly clear that texture out, and the game certainly doesn't stop trying to draw using it.

The only reason it's even an option to disable it is (a) some games actually need it to be off to show graphics for reasons we don't know yet, and (b) PC graphics cards usually slow down considerably when they need to render the scene twice, so playing without the extra effect can improve framerates in these cases.