[Public WebGL] WEBGL_debug_shader_precision extension proposal

Florian Bösch [email protected]
Thu Nov 6 05:04:52 PST 2014

On Thu, Nov 6, 2014 at 1:58 PM, Olli Etuaho <[email protected]> wrote:

>  The precision requirements for mediump and lowp are minimums, so a
> computation that a shader says should be performed at mediump precision is
> most often actually performed at the full 32-bit precision on desktop.
> Overall, anything in between 32-bit precision and 16-bit precision goes.
> And "anything in between" is not just a theoretical consideration - mobile
> devices have wildly different float formats and rounding behaviors, so
> testing on one spec-compliant mobile device does not even guarantee that a
> shader will work on other spec-compliant mobile devices.
I see, thanks for clearing that up.

> The extension does not require any support from the GL drivers, so that's
> why I've submitted the proposal only to the WebGL registry at this point.
> It can be implemented purely as a transformation of the GLSL code. If
> there's a strong reason for adding it also as a native extension, I have
> nothing against that, of course.
That makes sense. Though doesn't this mean it could essentially be done as
a JS library rather than an extension?

> I'll submit an amendment to the proposal to add an enable/disable toggle.
> I'll make it so that the emulation is enabled by default once the extension
> is enabled, but can be toggled off.
Well toggled on/off for individual shaders. Or toggled on/off globally. I'd
imagine what you'd do is 1) toggle it on for all 2) see an issue 3) toggle
it on for some to track track down the issue.
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