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



On Tue, Aug 30, 2011 at 10:02 PM, Mark Callow <callow_mark@hicorp.co.jp> wrote:
> The fundamental issue is that rendering to an FP framebuffer takes a lot of
> additional transistors. Because of this, I doubt if any OpenGL ES 2.0
> implementations support rendering to an FP framebuffer. It is likely found
> only on desktop OpenGL. This is also why OES_texture_floatadds only float
> texture support not FP framebuffer support.

Page 5 of the NVidia Tegra GL ES 2 docs
<http://developer.download.nvidia.com/tegra/docs/tegra_gles2_development.pdf>
indicates FP texture write support (and MRT fwiw). Adreno 220 series
can do deferred lighting and cloth sim which would also seem to
indicate FP texture write support.

David

> Regards
>
> -Mark
>
> On 2011/08/30 17:31, Kenneth Russell wrote:
>
> Understood -- I was actually looking at the 2.0.25 spec.
>
> To resolve the issue of rendering to floating-point textures, I
> propose defining a pair of OpenGL ES 2.0 extensions
> ("OES_render_texture_float" / "OES_render_texture_half_float"?) which
> define support for FLOAT and HALF_FLOAT_OES texture attachments to
> FBOs. Does that sound like a reasonable path to take at this point in
> time? I think that adding the minimal amount of spec text and
> functionality would be the best direction to take. For example, it
> doesn't seem necessary to provide control over clamping behavior.
>
> Another option would be to extend the WebGL extensions exposing
> OES_texture_float and OES_texture_half_float ([1], [2]) with enough
> language to allow, but not require, an implementation to support these
> texture types as FBO color attachments.
>
> I think that we should preserve the capability to render to
> floating-point textures from WebGL wherever possible. Existing use
> cases ([3], [4], [5], [6], and I'm sure there are more) demonstrate
> how compelling this capability is.
>
> [1] http://www.khronos.org/registry/webgl/extensions/OES_texture_float/
> [2] http://www.khronos.org/registry/webgl/extensions/OES_texture_half_float/
> [3] http://www.ibiblio.org/e-notes/webgl/gpu/contents.htm
> [4] http://madebyevan.com/webgl-path-tracing/
> [5] http://madebyevan.com/webgl-water/
> [6] http://webglsamples.googlecode.com/hg/hdr/hdr.html
>
> -Ken
>

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