opinions on buffer usage/draw calls for a scrolling album art program

Graphics and GPU Programming Programming

Started by trs79 July 06, 2013 02:49 AM

5 comments, last by trs79 10 years, 9 months ago

trs79

126

Author

July 06, 2013 02:49 AM

Hello,

I'm planning on creating a program whereby a list of album names is retrieved via http. Once the names are received, I plan to do the following:

Create a static VBO, with one quad for each album name. Each quad shares part of a texture atlas, so I can use a single draw call
There will be additional http requests for album art images
Display a loading indicator until image arrives, then lock part of dynamic texture atlas and write image data
There will be a scissor clipping rectangle that will hide the quads not yet shown
User can scroll list up and down

Questions:

I'm using GLES, is there a better way to handle the asynchronous incoming images then to use a dynamic texture with locking overhead?
Instead of one VBO for a single draw call, I could issue a separate draw call for each quad, not sure if this would be much slower? I think it would be easier because I could simply draw each quad with either album art texture or progress texture until image comes in

Thanks for any help, please see image below

froop

642

July 06, 2013 12:39 PM

Seems over optimized to me. I'd do a draw call for each album, unless there are thousands visible at the same time.

Norman Barrows

7,180

July 06, 2013 04:50 PM

i would probably just download an image into a buffer in ram, when the transfer was complete, copy it to a NON-DYNAMIC texture. then use sprites to draw. no locks, no vertex buffers, none of that BS. after all, you're just showing bitmaps.

Norm Barrows

Rockland Software Productions

"Building PC games since 1989"

rocklandsoftware.net

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marcClintDion

435

July 07, 2013 06:26 AM

Hopefully anyone else who posts here will have advice on how to optimize texture data uploads.

It appears to me that you should not be the least bit concerned about VBO performance or optimization. Even the weakest GPU's that I've tested can handle way more than what you are describing by a long shot, so far as models are concerned. The image data is another matter, I think that all of your performance concerns should be focused on your images not the quads, the quads can all be the same VBO anyways, just assign the particular image before making the draw call to the same VBO.

Maybe PBO's will be useful to you. They don't have much performance benefit for static textures but for situations where things are changing a lot there can be a 2x-3x increase in transfer speed to the GPU.

The following is an example on how to swap between two PBO's to help eliminate stalling, it's kind of like double buffering.

http://www.songho.ca/opengl/gl_pbo.html

The following is some data collected by nVidia engineers on PBO performance using various texture formats. Don't expect these results to be consistent across all GPU manufacturers.

http://http.download.nvidia.com/developer/Papers/2005/Fast_Texture_Transfers/Fast_Texture_Transfers.pdf

You will, however, gain some insight into what factors can influence performance in these matters. Look at the chart that has timing measurements for different texture formats. Specifically, for nVidia, using BGRA can be more than 3x faster than using RGBA, but this is for nVidia. You cannot expect these same results for ATI or PowerVR or Mali, etc....

This idea in it's essence will hold true, test all formats on your preferred platform and you are bound to find one that works best for the device that you are targeting.

Consider it pure joy, my brothers and sisters, whenever you face trials of many kinds, 3 because you know that the testing of your faith produces perseverance. 4 Let perseverance finish its work so that you may be mature and complete, not lacking anything.

trs79

126

Author

July 08, 2013 04:53 PM

Thanks for the responses everyone.

@froop:

Yeah, I think over-optimization is to blame here, I hate it when that happens. A draw call for each album seems like the way to go

@Norman Barrows:

Thanks for the tip about sprites, I had forgotten about those. So it sound sounds like you're also saying to use a draw call per album, but using point sprites instead of quads?

@marcClintDion:

PBO's sound interesting, but unfortunately they don't seem to be supported in GLES 2 that I'm targeting. I wish they were though, sounds like that would be the best way to update the textures