What Exactly Is This Old EFB Bug?

[coolitic]

For as long as I could remember, Metroid Prime Trilogy suffered from a problem with higher IR where either the top left quarter of the screen stayed effectively at 1x IR with Scaled EFB disabled, or there would be potentially serious bloom offset problems with it enabled. When I reported this bug, a dev responded and mentioned that they were aware that there was a problem with the EFB that was causing such problems.

Given that this is one of the only 2 significant issues I have in Metroid Prime Trilogy (the other being shader-gen stuttering), I am curious, what exactly is the nature of this long-standing bug?

[mimimi]

It's not a bug, it's how the game works. For some reason it copies the top left quarter of the screen and renders that as an efb copy in front of the actual picture. Now with scaled efb off, efb copies only use the native resolution, which is why that efb copy is at native resolution then. With scaled efb on, that efb copy is in the same resolution as the picture behind it, so there's no difference, or at least no difference people notice.

[coolitic]

(12-08-2016, 01:04 AM)mimimi Wrote: It's not a bug, it's how the game works. For some reason it copies the top left quarter of the screen and renders that as an efb copy in front of the actual picture. Now with scaled efb off, efb copies only use the native resolution, which is why that efb copy is at native resolution then. With scaled efb on, that efb copy is in the same resolution as the picture behind it, so there's no difference, or at least no difference people notice.

So it's copying some transparent UI elements which causes the entire top left to be pixellated?

And what is causing the bloom to offset abnormally with scaled efb copies on?

[JMC47]

Nothing; it's just that they're higher resolution so the blurring ends up just looking like stuff is further away. Because it's sharp and not blurred as much.

[coolitic]

(12-11-2016, 02:40 AM)JMC47 Wrote: Nothing; it's just that they're higher resolution so the blurring ends up just looking like stuff is further away.  Because it's sharp and not blurred as much.

Is there a way to tie blur scaling with the IR multiplier when scaled efb is enabled?

In the issue thread, you mentioned that the issue is possibly related to a flaw in EFB copies to Texture, but if that's the case, then wouldn't it go away when EFB to RAM is enabled? (which, by the way, is required to be enabled because EFB-to-Texture breaks visors)

[JosJuice]

Enabling EFB to RAM doesn't disable EFB to texture. If it had been possible to use EFB to RAM without EFB to texture, the output wouldn't be any more high-res than when Scaled EFB Copies is disabled.

[drhycodan]

I thought that was called hybrid efb and it's suppose to work that way.

[JMC47]

Yeah, EFB2RAM path isn't pure EFB2RAM, it's a hybrid method. Pure EFB2RAM = no upscaling on any EFB Effects.

[coolitic]

My question still stands, however: If the bloom offset artifact is caused by improper blur scaling, would one be able to tie blur scaling with the IR multiplier in Scaled EFB?

[JMC47]

Question: How do you detect which EFB effects to blur? Some people like sharpening up things like reflections.