[Public WebGL] Non-binding context creation attributes, specifically 'stencil'

Cedric Vivier [email protected]
Tue Apr 17 07:07:49 PDT 2012


On Tue, Apr 17, 2012 at 05:45, Jeff Gilbert <[email protected]> wrote:
> This demo which works 'correctly' in Chrome does not work in Firefox:
> http://www.playtankworld.com/demo/stencil_shadows
>
> This is because the author does not request a stencil buffer at context creation. In the absence of a selection, the context creation hint 'stencil' defaults to false. However, 'antialias', 'depth', and 'stencil' are non-binding hints. That is, a compliant implementation can ignore them.
>
> While this is necessary for when such buffers are not available, it is also allowable to always supply such buffers, even when they are (implicitly or explicitly) not requested.

I don't think the Chrome behavior is acceptable.
Sure, the WebGL implementation is indeed allowed to create an
underlying (GL/D3D/...) context with a stencil buffer by default, and
the WebGL implementation can ignore the request to create a context
with stencil buffer (thus returning a context without it).

On the other hand, when a stencil buffer has not been explicitly
requested, the stencil buffer should not be manipulatable from the
WebGL context (ie. "If the value is false, no stencil buffer is
available." as written in the spec), regardless of its actual presence
or not in the underlying context.

Regards,

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