681903 - [WebGL] please allow readPixels() for float

Status: RESOLVED INVALID

(Core :: Graphics: CanvasWebGL, enhancement)

Description

[Christian]

User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/13.0.782.215 Safari/535.1

Steps to reproduce:

Although floating point textures are supported through the following extension:
gl.getExtension("OES_texture_float");

it is not possible to read back the pixels from the framebuffer. using readPixels does only work für UNSIGNED_BYTE (as described in the spec.).

var pixels = new Float32Array(framebuffer.width * framebuffer.height * 4);
gl.readPixels(0, 0, framebuffer.width, framebuffer.height, gl.RGBA, gl.FLOAT, pixels);


Actual results:

Warning: WebGL: ReadPixels: type: invalid enum value 0x1406


Expected results:

an extension to the specified behaviour to allow a read back of float values would be desireable.

Comment 1

[Cedric Vivier [:cedricv]]

Can you do this under another implementation? Chrome?

If not, this is more of a specification issue, please discuss this on the WebGL mailing list at http://www.khronos.org/webgl/public-mailing-list/

Thanks,

Comment 2

[Christian]

a similar request exists for chrome:
https://code.google.com/p/chromium/issues/detail?id=74271

unfortunately the specification of OES_texture_float, does not mention the interaction with readPixels() although i think this would be a desirable feature.
http://www.khronos.org/registry/gles/extensions/OES/OES_texture_float.txt

I will get in touch with the WebGL mailing list.

best regards

Comment 3

[Benoit Jacob [:bjacob] (mostly away)]

Please do ask the WebGL public mailing list, it's a good question.

On my side I'm leaning towards supporting that, provided that drivers do. This seems like a useful feature.