Structured buffer float compression

Hyunkel · 2012-06-07T09:56:55

I have a computer shader that generates procedural planetary terrain and stores vertices in a structured buffer which has the following layout. struct PlanetVertex { float3 Position; float3 Normal; float Temperature; float Humidity; }; That's 10 floats with 4 bytes per float -> 40 bytes per vertex. A terrain node or patch contains 33x33 vertices, which is 43560 bytes. At the highest quality setting, the compute shader will output up to 5000 nodes, so the buffer needs to be 5000 * 43560 bytes, which is 217800000 bytes or ~207mb. Due to the way I handle load balancing between rendering and terrain generation, I need to have this buffer in memory twice, so I use ~415mb only for vertex data. This is okay I guess, since a planet is sort of the primary object, but I want to reduce this buffer size if possible. For example the normal vector: It doesn't need 32bit precision per channel, 16 would be more than enough. As for temperature and humidity, they could even fit in an 8bit unorm, but I doubt that's available here. I found that there are f32tof16 and f16tof32 functions in hlsl, which I assume are what I need, but I cannot quite figure out how they're supposed to work: http://msdn.microsoft.com/en-us/library/windows/desktop/ff471399(v=vs.85).aspx It says here that f32to16 returns a uint, but isn't that 32 bit as well? Cheers, Hyu

Graphics and GPU Programming Programming

Started by Hyunkel June 05, 2012 10:12 AM

19 comments, last by Hyunkel 11 years, 10 months ago

Hyunkel

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June 07, 2012 09:56 AM

[quote name='Hyunkel' timestamp='1338996087' post='4946776']
Well... no. I have not.
Do I have to consider this with structured buffers?

No, you don't. It's totally legal to access structures with a stride that's not a multiple of 16 bytes.
[/quote]
Thanks.

Hyunkel, yes, I'm familiar with DX11 compute shaders. You don't necessarily need to use StructuredBuffer UAV. You can use several UAVs as outputs of your compute shaders. So instead of a stream (array) of packed interleaved struct data, you might have streams (arrays) of individual struct members. Instead of 1 RWStructuredBuffer, you'd have 4 RWBuffers as targets of your compute shader. The main disadvantage I see is that you use 4 target slots instead of 1 (there should always be at least 8 supported, if I recall well). I believe you can have texture/buffer UAVs as well in cs_5_0 (unlike cs_4_1) but I've actually used RWStructuredBuffer just like you.

Oh, you can use the standard storage formats with RWBuffers?
For some reason I never thought of that.
That does make things a lot easier indeed.
I'll have to see if that performs just as well, but I see no reason why it wouldn't, and the memory footprint should obviously be quite a bit lower.

Thanks for pointing this out!

Structured buffer float compression

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Structured buffer float compression

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