HALF_FLOAT textures on Android

[Evgeny Demidov]

"R16F, RG16F, RGBA16F, R32F, RG32F, and RGBA32F all become valid render target formats when the EXT_color_buffer_float extension (WebGL 2.0) is enabled.
They should all be well supported on all platforms - though Android will probably only support the 16-bit formats." Ken Russell

if they "only support the 16-bit formats". How do they set Uint16Array HALF_FLOAT data then? I know it is easy with one simple shader but this is not very convenient. Or do they use FLOAT textures (e.g. in TensorFlow.js) ?

Any news about Float16Array discussion? JS progresses rapidly now. x2 accelerations (for free), remember ML, tensor cores and so on...   :)

Evgeny

[Jeff Gilbert]

You can upload Float32Arrays into HALF_FLOAT textures.

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[Evgeny Demidov]

just tested on Canary

   gl.texSubImage2D(gl.TEXTURE_2D, 0, 0,0, n,n, gl.RED, gl.HALF_FLOAT,pix)

with Float32Array pix and get

INVALID_OPERATION: texSubImage2D: type HALF_FLOAT_OES but ArrayBufferView is not NULL and not Uint16Array

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[Jeff Gilbert]

Guess we should really fix that. That's ES3's solution.

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[Evgeny Demidov]

in Firefox

Error: WebGL warning: texSubImage2D: ArrayBufferView type not compatible with `type`.

Old working true HALF_FLOAT texture test with Uint16Array

https://www.ibiblio.org/e-notes/webgl/gpu/tex2_16.htm

Evgeny

[Evgeny Demidov]

It would be nice if one can upload Float32Arrays into HALF_FLOAT textures, Compute SSBO buffers and back! :)

May be it works on Android?

[Evgeny Demidov]

can you make Float16ArrayANGLE extension?

For Android, TF.js PoseNet Model and Google Pixel :)

[Jeff Gilbert]

So in WebGL2, this is how it's done:
https://jsfiddle.net/jLzeq35a/

You can upload RED+FLOAT into R16F internalFormat textures.

[Ken Russell]

Good point Jeff.

Evgeny, we would rather not change WebGL 1.0's semantics further given that WebGL 2.0 provides a solution to this issue. Does using WebGL 2.0 work for you?

[Evgeny Demidov]

You will laugh "these Russians will always break something or lose" :)
I can upload RED+FLOAT into R16F internalFormat textures but can not get data back
https://www.ibiblio.org/e-notes/webgl/gpu/HALF_FLOATtest.htm
I get from
gl.readPixels(0,0, n,n, gl.RED, gl.FLOAT, pix)

ERROR :GL_INVALID_OPERATION : glReadPixels: format and type incompatible with the current read framebuffer

or for gl.HALF_FLOAT
readPixels: type HALF_FLOAT but ArrayBufferView not Uint16Array

Evgeny

[Evgeny Demidov]

Fortunately reading from HALF_FLOAT textures is not very important for matrix multiplications (Android, PoseNet TF.js Model and Google Pixel).
For NxN matrix multiplications C = AxB there are N^3 A,B readings and only N^2 C writings. Therefore shader can read HALF_FLOAT and write FLOAT values.

It may be caveats with HALF_FLOAT 32bit stride alignment on different GPU. E.g. I get acceleration with HALF_FLOAT on Nvidia and didn't get on Intel GPU.

SSBO buffers need to test too. Now Compute shaders read/write with 32bit stride but how it will read/write vec4 HALF_FLOAT data?

Evgeny

[Jeff Gilbert]

You're gonna need to read that back as RGBA/FLOAT or the implementation color read format/type, which is probably RED/HALF_FLOAT. ReadPixels format/type are restricted to these two combos.

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[Evgeny Demidov]

Thank you Jeff. All works fine for RGBA16F textures and RGBA/FLOAT ReadPixels format/type.

Evgeny

[Jeff Gilbert]

Just to be extra clear, you can call ReadPixels(RGBA, FLOAT) on an
R16F texture, but it might be worth it to you to read directly as
RED/HALF_FLOAT, if expanding R16F to RGBA/FLOAT is too slow:
https://jsfiddle.net/a4Lep9cj/5/

[Evgeny Demidov]

what is the use of

console.assert(g.checkFramebufferStatus(g.FRAMEBUFFER) == g.FRAMEBUFFER_COMPLETE);

console.assert(!g.getError());

if all the same I see ERRORs messages in console

I'm using alert() usually but not sure what is better 

[Jeff Gilbert]

It's a less common conditional version of console.log:

https://developer.mozilla.org/en-US/docs/Web/API/Console/assert

On my Windows+Firefox, I get no errors.

[Evgeny Demidov]

if I deliberately add an error (say "t" -> "t1") I get in Firefox

Assertion failed: jeff.htm:10:1

Assertion failed: jeff.htm:15:1

Via RGBA/FLOAT: 0 jeff.htm:25:1

Error: WebGL warning: texImage2D: Invalid internalformat: 0x0000 jeff.htm:9:1

it is likely just duplication?

[Evgeny Demidov]

Thank you, it is obvious but I missed (again :) that I can read pixels from "RED" FBO as RGBA

and really it may be a little slower.

On Saturday, April 20, 2019 at 6:59:55 AM UTC+3, Jeff Gilbert wrote: