extension.xml - mozsearch

<?xml version="1.0"?>

<draft href="EXT_texture_compression_rgtc/">

  <name>EXT_texture_compression_rgtc</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>39</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_rgtc.txt">

      EXT_texture_compression_rgtc</a> OpenGL extension to WebGL. Consult that extension

      specification for behavioral definitions, including error behaviors.

    </p>

<p>

      Updates of partial tiles detailed in the "Implementation Note" section of the

      EXT_texture_compression_rgtc specification must be supported in an implementation of this

      WebGL extension.

    </p>

    <features>

      <feature>

        Compression formats <code>COMPRESSED_RED_RGTC1_EXT</code>,

        <code>COMPRESSED_SIGNED_RED_RGTC1_EXT</code>,

        <code>COMPRESSED_RED_GREEN_RGTC2_EXT</code>,

        and <code>COMPRESSED_SIGNED_RED_GREEN_RGTC2_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>The following format-specific restrictions must be enforced:</p>

        <dl>

          <dt>COMPRESSED_RED_RGTC1_EXT</dt>

          <dt>COMPRESSED_SIGNED_RED_RGTC1_EXT</dt>

          <dd><p>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) * 8

          </code></blockquote>

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

          </dd>

          <dt>COMPRESSED_RED_GREEN_RGTC2_EXT</dt>

          <dt>COMPRESSED_SIGNED_RED_GREEN_RGTC2_EXT</dt>

          <dd><p>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>

          </dd>

          </dl>

      </feature>

    </features>

  </overview>

  <idl xml:space="preserve">

[NoInterfaceObject]

interface EXT_texture_compression_rgtc {

    const GLenum COMPRESSED_RED_RGTC1_EXT = 0x8DBB;

    const GLenum COMPRESSED_SIGNED_RED_RGTC1_EXT = 0x8DBC;

    const GLenum COMPRESSED_RED_GREEN_RGTC2_EXT = 0x8DBD;

    const GLenum COMPRESSED_SIGNED_RED_GREEN_RGTC2_EXT = 0x8DBE;

};

  </idl>

  <newtok>

    <function name="compressedTexImage2D">

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

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

      <code>COMPRESSED_RED_RGTC1_EXT</code>,

      <code>COMPRESSED_SIGNED_RED_RGTC1_EXT</code>,

      <code>COMPRESSED_RED_GREEN_RGTC2_EXT</code>,

      <code>COMPRESSED_SIGNED_RED_GREEN_RGTC2_EXT</code>

      <br/>

    </function>

    <function name="compressedTexSubImage2D">

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

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

      <code>COMPRESSED_RED_RGTC1_EXT</code>,

      <code>COMPRESSED_SIGNED_RED_RGTC1_EXT</code>,

      <code>COMPRESSED_RED_GREEN_RGTC2_EXT</code>,

      <code>COMPRESSED_SIGNED_RED_GREEN_RGTC2_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

      <code>COMPRESSED_RED_RGTC1_EXT</code> or <code>COMPRESSED_SIGNED_RED_RGTC1_EXT</code>

      and the byteLength of the ArrayBufferView is not:

      <blockquote><code>

        ceil(width / 4) * ceil(height / 4) * 8

      </code></blockquote>

    </error>

    <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

      <code>COMPRESSED_RED_GREEN_RGTC2_EXT</code> or <code>COMPRESSED_SIGNED_RED_GREEN_RGTC2_EXT</code>

      and the byteLength of the ArrayBufferView is not:

      <blockquote><code>

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

      </code></blockquote>

    </error>

  </errors>

  <history>

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

      <change>Initial revision.</change>

    </revision>

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

      <change>Rename to EXT_texture_compression_rgtc from WEBGL_compressed_texture_rgtc</change>

    </revision>

  </history>

</draft>