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



On Thu, May 20, 2010 at 09:45, Kenneth Russell <kbr@google.com> wrote:
> 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,

Hmm this would be something to verify, the specification of the
parameter does not imply your assumption.
Again, is there anything in OpenGL and ES specifications that require
texture parameters to have an immediate effect ? As far as I know,
this is not the case.

> 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.

Okay, let's consider OES_draw_texture extension which defines another
texture parameter :

"""
  TEXTURE_CROP_RECT_OES    4 integers       any value

  The texture parameter TEXTURE_CROP_RECT_OES controls the
  operation of DrawTex{sifx}[v]OES(), as described in
  section 5.7.  It has no effect on the rasterization of
  other primitives.
"""

For this one, a new value is only acted upon at the next DrawTexOES
call, so no immediate effect as well.


> This proposal is not workable.

The behavior and immediacy or not of the parameter can be defined in
the parameter specification, as demonstrated with both parameters
above, in absence of a definitive requirement from GL or ES spec to
have immediate effect on new parameter values.


Regards,
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