PowerVR serious problem

[Laska]

Unfortunately I still cannot manage it. I would like to be a solution...

[Laska]

Still no change. Will this ever be fixed?

[AlphaKennyTime]

(07-24-2014 02:55 PM)emualador Wrote:  I feel the same ,any solution?

This almost looks like a problem I had in some Naruto game. Disable "Simulate Block Transfer" it should be right under the buffered/non buffered setting.

[Laska]

Sadly this solution also didn't help at all.
I've found that another two games are nearly unplayable: in DIRT 2 and Sega Rally all cars are invisible.
Furthermore, in recently version some textures are very pixelated like road in Colin McRae or background in Worms 2.
Surprisingly, speed and performance in most games are very good on my device but because of this graphical glitches only 2 of my 9 games are playable.
Please developers, is there any chance to resolve this issue? Please help!
Thank you in advance!

[Laska]

Hello again!
I don't wanna be pain in the arse but is there any (maybe temporary) solution for this problem? Most of racing games are still unplayable on sgx 540 because of missing parts of the road or invisible cars.

[[Unknown]]

Well, said hack has been removed. It's unfortunate that PowerVR is still not working well.

-[Unknown]

[Laska]

(12-30-2014 05:25 PM)[Unknown] Wrote:  Well, said hack has been removed. It's unfortunate that PowerVR is still not working well.

-[Unknown]

What do you mean by "hack has been removed"?

[[Unknown]]

The hack I mentioned earlier that made PowerVR use a different and definitely wrong method of alpha testing. Now it uses an alternate method that works on PowerVR (or at least I think it does.) So, at least that's one problem gone.

Unfortunately alpha testing is still, afaik, quite slow on PowerVR. But if you have alpha test disabled you'll definitely get even more graphical glitches.

-[Unknown]

[Laska]

(12-30-2014 07:00 PM)[Unknown] Wrote:  The hack I mentioned earlier that made PowerVR use a different and definitely wrong method of alpha testing. Now it uses an alternate method that works on PowerVR (or at least I think it does.) So, at least that's one problem gone.

Unfortunately alpha testing is still, afaik, quite slow on PowerVR. But if you have alpha test disabled you'll definitely get even more graphical glitches.

-[Unknown]

Can you recommend any method or hack to change this? This glitch makes the most game unplayable because you cannot say what's going on on the screen, I.E. car is invisible, opponents are invisible etc.. Please, it would be very helpful!

[[Unknown]]

If you're talking about alpha testing, the problem is that it does something the PowerVR chip doesn't like. It's the operation in the first place that is bad. Actually, alpha testing in general is sorta "deprecated" and most modern games won't be using it; but it worked fine on the PSP so it's used all the time by a ton of games.

The basic idea is this: let's say I have a texture where some of the pixels are partially transparent. Like a shadow or something. Alpha testing allows it to say "only draw the parts that are AT LEAST this opaque." So it might only draw the darkest parts of the shadow, skipping the lighter parts of the shadow entirely.

That particular example is probably one where you'd say "it's not so bad if we disable the effect entirely." There are other much more complicated things that are done with alpha testing (that are more necessary for graphics to look even close to right), though. This is just an easy to understand example.

Anyway, the problem is that the GPU just wants to DRAW. It doesn't want someone constantly grabbing it's arm and saying "hey wait, not that one. You have to skip that pixel." This makes PowerVR especially very slow, because it's not built to stop-and-go like that (and, as I mentioned, it's somewhat of an antiquated practice to make the gpu do that.)

If someone were to redo the way the game draws things, and make it use more modern techniques, the problem would go away. That wouldn't be emulation though, that would be a port or a remake.

Aside from that though, the PowerVR SGX540 and 544 have not terribly good precision in shaders. One thing was fixed recently by replacing a modulus (remainder of division) math operator with a function that did _exactly_ what the spec _requires_ the modulus operator to be equivalent to. So some of the mathematics on the gpu (or its drivers, hard to tell) don't actually have correct results. That's kinda scary, and makes it hard to make things come out right, especially when a lot of PSP games do really neat tricks to get 150% out of the PSP hardware, and we have to translate these neat tricks into things that work on OpenGL.

We may be able to find ways to workaround the bad math and precision in that GPU, but ultimately it's just going to make things slower, not faster, because we will have to do more complicated things or do them in more steps or in multiple ways to get the precision necessary for things to actually work and show up.

-[Unknown]

[The Phoenix]

Thanks for the explanation Unknown, explains why things don't look as good as other devices on many of the games, in a way using my PowerVR for testing games is not going to benefit us to be honest, as the games may work far better on other peoples devices, if you see what I mean , and so may give false results on Android.

[Laska]

(01-12-2015 02:03 AM)[Unknown] Wrote:  If you're talking about alpha testing, the problem is that it does something the PowerVR chip doesn't like. It's the operation in the first place that is bad. Actually, alpha testing in general is sorta "deprecated" and most modern games won't be using it; but it worked fine on the PSP so it's used all the time by a ton of games.

The basic idea is this: let's say I have a texture where some of the pixels are partially transparent. Like a shadow or something. Alpha testing allows it to say "only draw the parts that are AT LEAST this opaque." So it might only draw the darkest parts of the shadow, skipping the lighter parts of the shadow entirely.

That particular example is probably one where you'd say "it's not so bad if we disable the effect entirely." There are other much more complicated things that are done with alpha testing (that are more necessary for graphics to look even close to right), though. This is just an easy to understand example.

Anyway, the problem is that the GPU just wants to DRAW. It doesn't want someone constantly grabbing it's arm and saying "hey wait, not that one. You have to skip that pixel." This makes PowerVR especially very slow, because it's not built to stop-and-go like that (and, as I mentioned, it's somewhat of an antiquated practice to make the gpu do that.)

If someone were to redo the way the game draws things, and make it use more modern techniques, the problem would go away. That wouldn't be emulation though, that would be a port or a remake.

Aside from that though, the PowerVR SGX540 and 544 have not terribly good precision in shaders. One thing was fixed recently by replacing a modulus (remainder of division) math operator with a function that did _exactly_ what the spec _requires_ the modulus operator to be equivalent to. So some of the mathematics on the gpu (or its drivers, hard to tell) don't actually have correct results. That's kinda scary, and makes it hard to make things come out right, especially when a lot of PSP games do really neat tricks to get 150% out of the PSP hardware, and we have to translate these neat tricks into things that work on OpenGL.

We may be able to find ways to workaround the bad math and precision in that GPU, but ultimately it's just going to make things slower, not faster, because we will have to do more complicated things or do them in more steps or in multiple ways to get the precision necessary for things to actually work and show up.

-[Unknown]

Thank you so much for your answer!!!
I would love to see some optional (that can be disable on a non-powervr devices) hack to manage this problem. I must say that most games on my phones runs with decent speed and looks very good and only those graphical glithes makes couple of them unplayable.
Thanks in advance!

[Laska]

Could anyone tell me is this ever gonna be fixed or is it hopeless situation? Now most of games running on my device with pretty acceptable speed but this glitches making lot of them unplayable because of the messed-up screen...

[fivefeet8]

(01-12-2015 02:03 AM)[Unknown] Wrote:  Anyway, the problem is that the GPU just wants to DRAW. It doesn't want someone constantly grabbing it's arm and saying "hey wait, not that one. You have to skip that pixel." This makes PowerVR especially very slow, because it's not built to stop-and-go like that (and, as I mentioned, it's somewhat of an antiquated practice to make the gpu do that.)


-[Unknown]

Do you think this is related to the fact that PowerVR GPu's are using tile based rendering instead of immediatate rendering like most other GPus? I remember earlier Tile Based Rendering PC video cards having similar issues with PC games at the time.

[[Unknown]]

Yes, I think so.

-[Unknown]