extension.xml - mozsearch

<?xml version="1.0"?>

<draft href="EXT_texture_compression_bptc/">

  <name>EXT_texture_compression_bptc</name>

  <contact>

    <a href="https://www.khronos.org/webgl/public-mailing-list/">WebGL working group</a> (public_webgl 'at' khronos.org)

  </contact>

  <contributors>

    <contributor>Olli Etuaho, NVIDIA</contributor>

    <contributor>Members of the WebGL working group</contributor>

  </contributors>

  <number>38</number>

  <depends>

    <api version="1.0"/>

  </depends>

  <overview>

<p>

      This extension exposes the compressed texture format defined in the

      <a href="https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_texture_compression_bptc.txt">

      EXT_texture_compression_bptc</a> OpenGL ES extension to WebGL. Consult that extension

      specification for behavioral definitions, including error behaviors.

    </p>

<p>

      Sampling from textures in the COMPRESSED_SRGB_ALPHA_BPTC_UNORM_EXT format performs a color space

      conversion as specified for SRGB textures in the

      <a href="https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_sRGB.txt">EXT_sRGB</a> OpenGL ES

      extension.

    </p>

    <features>

      <feature>

        Compression format <code>COMPRESSED_RGBA_BPTC_UNORM_EXT</code>,

        <code>COMPRESSED_SRGB_ALPHA_BPTC_UNORM_EXT</code>,

        <code>COMPRESSED_RGB_BPTC_SIGNED_FLOAT_EXT</code>,

        and <code>COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT_EXT</code> may be passed to

        the <code>compressedTexImage2D</code> and <code>compressedTexSubImage2D</code> entry points.

      </feature>

      <feature>

        Calling <code>getParameter</code> with the argument <code>COMPRESSED_TEXTURE_FORMATS</code>

        will include the formats from this specification.

      </feature>

      <feature>

<p>

          If the <code>internalformat</code> is one of the BPTC internal formats from this specification,

          the <code>byteLength</code> of the ArrayBufferView, <code>pixels</code>, passed to

          <code>compressedTexImage2D</code> or <code>compressedTexSubImage2D</code> must be

          equal to the following number of bytes:

        </p>

        <blockquote><code>

          ceil(width / 4) * ceil(height / 4) * 16

        </code></blockquote>

        <p>If it is not, an <code>INVALID_VALUE</code> error is generated.</p>

      </feature>

    </features>

  </overview>

  <idl xml:space="preserve">

[NoInterfaceObject]

interface EXT_texture_compression_bptc {

    const GLenum COMPRESSED_RGBA_BPTC_UNORM_EXT = 0x8E8C;

    const GLenum COMPRESSED_SRGB_ALPHA_BPTC_UNORM_EXT = 0x8E8D;

    const GLenum COMPRESSED_RGB_BPTC_SIGNED_FLOAT_EXT = 0x8E8E;

    const GLenum COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT_EXT = 0x8E8F;

};

  </idl>

  <newtok>

    <function name="compressedTexImage2D">

      <param name="internalformat" type="GLenum"/>

      Accepted by the <code>internalformat</code> parameter:

      <code>COMPRESSED_RGBA_BPTC_UNORM_EXT</code>,

      <code>COMPRESSED_SRGB_ALPHA_BPTC_UNORM_EXT</code>,

      <code>COMPRESSED_RGB_BPTC_SIGNED_FLOAT_EXT</code>,

      <code>COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT_EXT</code>

      <br/>

    </function>

    <function name="compressedTexSubImage2D">

      <param name="internalformat" type="GLenum"/>

      Accepted by the <code>internalformat</code> parameter:

      <code>COMPRESSED_RGBA_BPTC_UNORM_EXT</code>,

      <code>COMPRESSED_SRGB_ALPHA_BPTC_UNORM_EXT</code>,

      <code>COMPRESSED_RGB_BPTC_SIGNED_FLOAT_EXT</code>,

      <code>COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT_EXT</code>

      <br/>

    </function>

  </newtok>

  <errors>

    <error enum="INVALID_VALUE">

      The error <code>INVALID_VALUE</code> is generated by <code>compressedTexImage2D</code> and

      <code>compressedTexSubImage2D</code> if the <code>internalformat</code> parameter is one of the BPTC

      internal formats from this extension and the byteLength of the ArrayBufferView is not:

      <blockquote><code>

        ceil(width / 4) * ceil(height / 4) * 16

      </code></blockquote>

    </error>

  </errors>

  <history>

    <revision date="2018/09/14">

      <change>Initial revision.</change>

    </revision>

    <revision date="2018/09/18">

      <change>Moved to draft status.</change>

    </revision>

    <revision date="2018/09/26">

      <change>Retarget against EXT_texture_compression_bptc instead of ARB_texture_compression_bptc</change>

      <change>Rename to EXT_texture_compression_bptc from WEBGL_compressed_texture_bptc</change>

    </revision>

  </history>

</draft>