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Re: [Public WebGL] Move flipY and asPremultipliedAlpha parameters out of DOM helpers



On Wed, May 19, 2010 at 6:31 PM, Cedric Vivier <cedricv@neonux.com> wrote:
> On Thu, May 20, 2010 at 08:52, Kenneth Russell <kbr@google.com> wrote:
>> On Wed, May 19, 2010 at 5:38 PM, Cedric Vivier <cedricv@neonux.com> wrote:
>> Changes to texture parameters take effect immediately. There are no texture parameters which affect the behavior of later calls (for example to glTexImage2D) but whose changes are not otherwise seen.
>
> Change to texture parameters *values* take effect immediately yes!
> I strongly disagree that there is such a requirement for new values to
> be acted upon immediately.
>
> As a matter of fact I gave GL's GL_GENERATE_MIPMAP texture parameter
> as example, which is defined as :
>
> """
> GL_GENERATE_MIPMAP
> Specifies a boolean value that indicates if all levels of a mipmap
> array should be automatically updated when any modification to the
> base level mipmap is done. The initial value is GL_FALSE.
> """
>
> It is clear here that this parameter does _not_ take effect
> immediately as it generates mipmaps automatically "**when** any
> modification to the base level mipmap is done". "Modifications" here
> imply tex(Sub)Image2D calls, this texture parameter is indeed a way to
> avoid having to call glGenerateMipmaps after every modification.

If you call glTexImage2D and later enable the GL_GENERATE_MIPMAP
texture parameter for the texture object, then as far as I know, the
mipmaps are supposed to be generated immediately, the same way that
changing the wrap mode takes effect immediately. OpenGL ES 2.0
eliminated the GL_GENERATE_MIPMAP texture parameter, replacing it with
the explicit glGenerateMipmap, presumably because of ill defined
semantics.

This proposal is not workable.

-Ken
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