[Public WebGL] readPixles() can't access float values (OES_texture_float interaction)

Kenneth Russell [email protected]
Mon Sep 19 11:36:52 PDT 2011


On Mon, Sep 19, 2011 at 11:14 AM, Chris Marrin <[email protected]> wrote:
>
> On Sep 16, 2011, at 11:14 AM, Kenneth Russell wrote:
>
>>
>> Shouldn't the existing need to check the framebuffer's status be
>> sufficient? Applications that don't check for FBO completeness are by
>> definition incorrectly written. These applications already have to
>> request the floating-point texture extension from WebGL.
>
> Are you saying an author should discover whether or not it's possible to create a FP FBO by trying and if the FBO is incomplete after the attempt, that's an indication that it's not supported? I don't think that has precedence. Seems like it's much better to use the extension mechanism. If the attempt to enable the extension fails, then it's not a feature that can be used.

There is certainly precedence for this behavior; it's how FBOs work in
the OpenGL API. In OpenGL ES, only one combination of renderbuffer
attachments' formats is required to be supported, and what combination
that is is not defined (ES20 spec 2.0.25, Section 4.4.5, "Framebuffer
Completeness", p. 119). Applications are supposed to check FBO
completeness before rendering and try other combinations of
attachments if their preferred configuration isn't supported.

I'm not in favor of adding a WebGL-specific extension that has to be
separately enabled in order to attach FP textures to an FBO. If there
were an ES20 extension defining FP framebuffer support, that would be
a different question. Since there doesn't seem to be support in the ES
working group to define such an extension, and since there's at least
one piece of ES20 compliant hardware that exposes such support under
the umbrella of OES_texture_half_float, I think we should leave render
to FP texture support as an optional feature under WebGL's FP texture
extensions.

-Ken

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