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





On 11/09/19 11:39, Florian Bösch wrote:
On Mon, Sep 19, 2011 at 8:14 PM, Chris Marrin <cmarrin@apple.com> wrote:

Yes it's a bit messy. But the http://www.opengl.org/registry/specs/ARB/texture_float.txt makes no stipulation if framebuffers have to support it or not.
That cannot be used as a precedent because the extension predates FBOs. And, as I just pointed out in another email, there is a separate ARB extension introduced just after texture_float for rendering floats to the default framebuffer.
Likewise http://www.opengl.org/registry/specs/ARB/framebuffer_object.txt does not make any such guarantee, however it does discuss various use cases with floating point attached buffers, including color.

In my (limited, desktop oriented) practice I have not yet seen a device which supports floating point textures and FBOs, but cannot handle attaching a floating point texture to an FBO. So regardless of the intent of webgl, OpenGL does not support the query you'd like to execute. The only way to execute your desired "can this thing support floating point attachments" is to try it out, unless the extension registry is updated with just such an extension.
Float rendering has been required in desktop GL for some time. For the most part the WebGL implementation of a color_buffer_float extension can simply look at the GL version to determine if float rendering is supported. If support is unclear, it can set everything up and check framebuffer status, possibly saving a large number of application programmers having to do the same thing.

Regards

-Mark

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