[Mesa-dev] [PATCH] mesa: Add ARB_texture_view to Mesa core

[Courtney Goeltzenleuchter]

On Tue, Nov 5, 2013 at 12:22 PM, Ian Romanick <idr at freedesktop.org> wrote:

> On 11/05/2013 09:44 AM, Chris Forbes wrote:
> >> So, you can create a GL_LUMINANCE view of a GL_LUMINANCE texture.
>  Hmm...
> >
> > My understanding is you can't actually, since views can only be
> > created from immutable-format textures, and GL_LUMINANCE is not a
> > sized internalformat, so it can't be used with TexStorage?
>
> I was just using GL_LUMINANCE as shorthand for GL_LUMINANCE4,
> GL_LUMINANCE8, GL_LUMINANCE12, and GL_LUMINANCE16.  As far as I can tell,
>
>     glGenTextures(1, &tex);
>     glBindTexture(GL_TEXTURE_2D, tex);
>     glTexStorage2D(GL_TEXTURE_2D,
>                 8,
>                 GL_LUMINANCE8,
>                 1024, 1024);
>
> is perfectly valid.  Sayeth GL_ARB_texture_storage:
>
>     Accepted by the <internalformat> parameter of TexStorage* when
>     implemented on OpenGL ES:
>
>         ALPHA8_EXT                     0x803C
>         LUMINANCE8_EXT                 0x8040
>         LUMINANCE8_ALPHA8_EXT          0x8045
>
> I guess that means GL_LUMINANCE4, GL_LUMINANCE12, and GL_LUMINANCE16 are
> out.  As are all GL_INTENSITY formats.  There are still these three
> legacy formats to handle.
>
> So, if we support GL_ARB_texture_view in a compatibility profile,
>
>     glGenTextures(1, &view);
>     glTextureView(view,
>                 GL_TEXTURE_2D,
>                 tex,
>                 GL_LUMINANCE8,
>                 1, 1, 1, 1);
>
> is also valid.
>
> Right?
>

The spec is pickier than that.  For 8bit texels the allowed internal
formats are:  R8UI, R8I, R8, R8_SNORM
I use the table specified in the ARB_texture_view to translate the target
internalFormat passed to glTextureView into a VIEW_CLASS. GL_LUMINANCE8
does not have a valid VIEW_CLASS and could not match the internal format of
the source texture.

That makes me wonder, should I be trying to map the target internalformat
into a driver internal format?

Courtney


-- 
Courtney Goeltzenleuchter
LunarG
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