What's the limitation of texture memory for PowerVR SGX?

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What's the limitation of texture memory for PowerVR SGX?

(10 posts) (6 voices)

Started 1 year ago by slash
Latest reply from araker

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slash
Member

Hello guys. I'm developing games for iPhone 3GS and iPad.

Apple's official document introduce that the limitation of 24MB memory for texture. But it's for iPhone 3G.
Is there any limitation for iPhone 3GS and iPad?
I googled for more than 3 hours but get nothing.

Thanks.

'OpenGL ES applications targeting the PowerVR MBX must limit themselves to no more than 24 MB of memory for textures and renderbuffers. Overall, the PowerVR MBX is more sensitive to memory usage, and your application should minimize the size of textures and renderbuffers.'

Posted 1 year ago #
applehund
Member

Curious about this too! Thanks

Posted 1 year ago #
Dragyn
Member

Okay, I did a little sleuthing on this. The MBX was only used through the second generation iDevices (iPhone 3 and Ipod Touch 2nd Gen).

Everything after that uses PowerVR SGX.

I also found this quote, which I think answers your question:
"The iPhone 3GS has a unified memory system, which means that graphics resources can live anywhere in memory, without any limit."
http://mobileorchard.com/a-huge-leap-forward-graphics-on-the-iphone-3gs/

So it looks like as long as you're targeting 3GS or higher, then you can go off the total RAM on the device (from 256 MB for 3GS to 512 MB for iPhone 4) to determine how much you can use.

Posted 1 year ago #
applehund
Member

Sounds good dragyn, thanks for the reply!

Posted 1 year ago #
Robert Payne
Member

@Dragyn Have you tested that theory? As far as I know the 3GS is still limited to 4mb of texture data. Which is normally:

4mb for buffers ( 2mb frame and 2mb render )
5x 1024x1024 sprite sheets ( 4mb each )

I could be wrong. I know during my iPad development it has the same graphics chip and this limitation. The iPhone 4 I'm unsure about.

-Robert

Posted 1 year ago #
Andreas Loew
Member

http://developer.apple.com/library/ios/#documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/OpenGLESPlatforms/OpenGLESPlatforms.html

The maximum 2D or cube map texture size is 2048 x 2048. This is also the maximum renderbuffer size and viewport size.

Posted 1 year ago #
Dragyn
Member

@Robert - no, I don't have a 3GS to test with. I was under the impression that the unified memory (with the SGX set) gave you access to more total memory for graphics to be loaded. Going back to @slash's original post, I was interpreting this to be the total textures that could be loaded simultaneously, not the per-texture limit per se.

I thought that the maximum size per texture was 1024x1024 for older devices and 2048x2048 for iPhone 4 and newer, but that the total size of all loaded textures was dependent on the total memory of the device (for 3GS and newer).

Am I in error on this point? I haven't done any projects with more than 2 or 3 1024x1024 sprite sheets at this point, so I haven't hit any memory walls (yet).

I'll defer to you and @Andreas, since you're both a lot more graphics-savvy than I...

Posted 1 year ago #
araker
Moderator

@Robert, it is true what Dragyn said about the unified memory system in devices with a SGX chip. Like the docs state, all devices with the SGX chip can load 2028 x 2048 textures.

Posted 1 year ago #
Robert Payne
Member

@dragyn @andreasloew @araker

I was simply using 1024x1024 as an example for memory usage. According to those docs indeed the SGX chipset allows the full usage of all memory.. tests would prove what is actually possible.

-Robert

Posted 1 year ago #
araker
Moderator

@Robert, full usage is of course theoretically. Everything shares the same memory, so the free memory will depend on how much memory is available after each process has cleaned their caches (due to a memory warning). Personally I haven't gone beyond loading 3 2048 x 2048 sheets and one 1024 x 1024 sheet on my 3GS.

Posted 1 year ago #

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