[Mesa-dev] [PATCH] mesa: Use GL_RED for DEPTH_TEXTURE_MODE for everything but legacy GL.

[Ian Romanick]

On 12/19/2012 05:59 PM, Paul Berry wrote:
> On 19 November 2012 11:06, Kenneth Graunke <kenneth at whitecape.org
> <mailto:kenneth at whitecape.org>> wrote:
>
>     On 11/18/2012 05:43 PM, Ian Romanick wrote:
>
>         On Nov 17, 2012, at 11:26 PM, Kenneth Graunke
>         <kenneth at whitecape.org <mailto:kenneth at whitecape.org>> wrote:
>
>             According to page 163 of the ES 3.0 spec:
>
>             "Texture lookups involving textures with depth component
>             data generate
>             a texture base color C_b either using depth data directly or by
>             performing a comparison with the D_ref value used to perform the
>             lookup, as described in section 3.8.15.  The resulting value
>             R_t is
>             then expanded to a color C_b = (R_t,0,0,1), ..."
>
>             In other words, depth textures are supposed to be treated as
>             GL_RED.
>
>             A discussion about this text can be found in Khronos bugzilla:
>             https://cvs.khronos.org/__bugzilla/show_bug.cgi?id=7962
>             <https://cvs.khronos.org/bugzilla/show_bug.cgi?id=7962>
>
>             It's unclear what the behavior of desktop GL should be.  The
>             GL 3.x
>             specifications indicate that it should be (r, r, r, 1), which is
>             GL_LUMINANCE (the old default).  However, page 112 of the
>             4.2 core
>             specification contains the text quoted above, explicitly
>             declaring it
>             to be (R_t, 0, 0, 1), which is GL_RED.
>
>             So it hinges on whether the 4.2 text is a change or a
>             clarification.
>             Personally I think that using GL_RED in core contexts and
>             GL_INTENSITY
>             in legacy contexts seems reasonable.
>
>
>         I believe it was an intentional change somewhere in 4.x.  We may
>         want to select behavior based on API / version.
>
>
>     Ugh.  On further investigation, it turns out that OES_depth_texture
>     (which is ES2 only) does not provide DEPTH_TEXTURE_MODE, but
>     explicitly states that it should act as GL_LUMINANCE.  There's also
>     a conformance test for that.
>
>     So, for ES 2, it *must* be GL_LUMINANCE.  For ES 3, it *must* be RED.
>
>     Time to file spec bugs...
>
> Does anyone know if this ever got addressed?  I'm still seeing these
> GLES3 conformance failures.

There was some discussion, but I don't feel like there was any 
resolution.  I'll rattle the cage again...