[Mesa-dev] [PATCH 2/3] main: Checking for cube completeness in GetTextureImage.

[Laura Ekstrand]

I added a clearer explanation based on our irc discussion:

http://cgit.freedesktop.org/~ldeks/mesa/commit/?h=adsa-textures&id=db418437915bba959c0b6c8babe40f675bbdf31c

On Thu, Jan 1, 2015 at 11:15 AM, Chad Versace <chad.versace at intel.com>
wrote:

> On 12/31/2014 05:26 PM, Laura Ekstrand wrote:
> > This is part of a potential solution to Khronos Bug 13223.  Cube
> completeness
> > is a concept from glGenerateMipmap, but it seems reasonable to check for
> it in
> > GetTextureImage when the target is GL_TEXTURE_CUBE_MAP.
> > ---
> >  src/mesa/main/texgetimage.c | 41
> +++++++++++++++++++++++++++++------------
> >  1 file changed, 29 insertions(+), 12 deletions(-)
> >
> > diff --git a/src/mesa/main/texgetimage.c b/src/mesa/main/texgetimage.c
> > index 5b4d294..060c68a 100644
> > --- a/src/mesa/main/texgetimage.c
> > +++ b/src/mesa/main/texgetimage.c
> > @@ -1105,18 +1105,35 @@ _mesa_GetTextureImage( GLuint texture, GLint
> level, GLenum format,
> >                       "glGetTextureImage(insufficient cube map
> storage)");
> >           return;
> >        }
> > -      for (i = 0; i < 6; ++i) { /* For each face. */
> > -         if (!texObj->Image[i][level]) {
> > -            /* Not enough image planes for a cube map.  The spec does
> not say
> > -             * what should happen in this case because the user has
> always
> > -             * specified each cube face separately (using
> > -             * GL_TEXTURE_CUBE_MAP_POSITIVE_X+i) in previous GL
> versions.
> > -             * This is addressed in Khronos Bug 13223.
> > -             */
> > -            _mesa_error(ctx, GL_INVALID_OPERATION,
> > -                        "glGetTextureImage(insufficient cube map
> storage)");
> > -            return;
> > -         }
> > +
> > +      /*
> > +       * This is part of a potential solution to a bug in the spec.
> According
> > +       * to Section 8.17 Texture Completeness in the OpenGL 4.5 Core
> Profile
> > +       * spec (30.10.2014):
> > +       *    "[A] cube map texture is cube complete if the
> > +       *    following conditions all hold true: The [base level] texture
> > +       *    images of each of the six cube map faces have identical,
> positive,
> > +       *    and square dimensions. The [base level] images were each
> specified
> > +       *    with the same internal format."
> > +       *
> > +       * It seems reasonable to check for cube completeness of an
> arbitrary
> > +       * level here so that the returned data has a consistent format
> and size
> > +       * and therefore fits in the user's buffer.
> > +       */
>
> The above comment is very confusing, unless the reader has had a
> conversation with
> you about the topic ;). The comment alludes to a "bug in the spec" and "a
> potential solution",
> but the comment does not state what the bug is. The reader has to guess
> based on the clues
> you give. For the sake of the future devs, please directly describe the
> bug.
>
> > +      if (!_mesa_cube_level_complete(texObj, level)) {
> > +         /*
> > +          * Precedence for this error:
> > +          * In Section 8.14.4 Manual Mipmap Generation, the OpenGL 4.5
> Core
> > +          * Profile spec (30.10.2014) says:
> > +          *    "An INVALID_OPERATION error is generated by
> > +          *    GenerateTextureMipmap if the effective target is
> > +          *    TEXTURE_CUBE_MAP or TEXTURE_CUBE_MAP_ARRAY, and the
> texture
> > +          *    object is not cube complete or cube array complete,
> > +          *    respectively."
> > +          */
>
> I suggest removing the comment above. I don't believe you need to provide
> precedent
> for emitting GL_INVALID_OPERATION here, since it is a catch-all generic
> error.
> Just a suggestion.
>
> > +         _mesa_error(ctx, GL_INVALID_OPERATION,
> > +                     "glGetTextureImage(cube map incomplete)");
> > +         return;
> >        }
>
>
>
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