src/third_party/webgl/src/extensions/WEBGL_compressed_texture_atc/extension.xml

   1 <?xml version="1.0"?>
   2
   3 <draft href="WEBGL_compressed_texture_atc/">
   4   <name>WEBGL_compressed_texture_atc</name>
   5   <contact>
   6     <a href="https://www.khronos.org/webgl/public-mailing-list/">WebGL working group</a> (public_webgl 'at' khronos.org)
   7   </contact>
   8   <contributors>
   9     <contributor>Members of the WebGL working group</contributor>
  10   </contributors>
  11   <number>12</number>
  12   <depends>
  13     <api version="1.0"/>
  14   </depends>
  15   <overview>
  16     <p>
  17       This extension exposes the compressed texture formats defined in the
  18       <a href="http://www.khronos.org/registry/gles/extensions/AMD/AMD_compressed_ATC_texture.txt">
  19       AMD_compressed_ATC_texture</a> OpenGL extension to WebGL.
  20     </p>
  21     <features>
  22       <feature>
  23         Compression formats <code>COMPRESSED_RGB_ATC_WEBGL</code>,
  24         <code>COMPRESSED_RGBA_ATC_EXPLICIT_ALPHA_WEBGL</code>, and
  25         <code>COMPRESSED_RGBA_ATC_INTERPOLATED_ALPHA_WEBGL</code> may be passed to
  26         the <code>compressedTexImage2D</code> and <code>compressedTexSubImage2D</code> entry points.
  27
  28         These formats correspond to the 3 formats defined in the AMD_compressed_ATC_texture OpenGL
  29         extension. Although the enum names are changed, their numeric values are the same. The correspondence
  30         is given by this table:
  31         <table>
  32           <tr>
  33             <th>WebGL format enum</th>
  34             <th>OpenGL format enum</th>
  35             <th>Numeric value</th>
  36           </tr>
  37           <tr>
  38             <td>COMPRESSED_RGB_ATC_WEBGL</td>
  39             <td>ATC_RGB_AMD</td>
  40             <td>0x8C92</td>
  41           </tr>
  42           <tr>
  43             <td>COMPRESSED_RGBA_ATC_EXPLICIT_ALPHA_WEBGL</td>
  44             <td>ATC_RGBA_EXPLICIT_ALPHA_AMD</td>
  45             <td>0x8C93</td>
  46           </tr>
  47           <tr>
  48             <td>COMPRESSED_RGBA_ATC_INTERPOLATED_ALPHA_WEBGL</td>
  49             <td>ATC_RGBA_INTERPOLATED_ALPHA_AMD</td>
  50             <td>0x87EE</td>
  51           </tr>
  52         </table>
  53       </feature>
  54       <feature>
  55         Calling <code>getParameter</code> with the argument <code>COMPRESSED_TEXTURE_FORMATS</code>
  56         will include the 3 formats from this specification.
  57       </feature>
  58       <feature>
  59         <p>The following format-specific restrictions must be enforced:</p>
  60         <dl>
  61           <dt>COMPRESSED_RGB_ATC_WEBGL</dt>
  62           <dd><p>The <code>byteLength</code> of the ArrayBufferView, <code>pixels</code>, passed to
  63           either <code>compressedTexImage2D</code> or <code>compressedTexSubImage2D</code> must be
  64           equal to the following number of bytes:</p>
  65           <blockquote><code>
  66             floor((width + 3) / 4) * floor((height + 3) / 4) * 8
  67           </code></blockquote>
  68           <p>If it is not, an <code>INVALID_VALUE</code> error is generated.</p>
  69           </dd>
  70
  71           <dt>COMPRESSED_RGBA_ATC_EXPLICIT_ALPHA_WEBGL</dt>
  72           <dt>COMPRESSED_RGBA_ATC_INTERPOLATED_ALPHA_WEBGL</dt>
  73           <dd><p>The <code>byteLength</code> of the ArrayBufferView, <code>pixels</code>, passed to
  74           either <code>compressedTexImage2D</code> or <code>compressedTexSubImage2D</code> must be
  75           equal to the following number of bytes:</p>
  76           <blockquote><code>
  77             floor((width + 3) / 4) * floor((height + 3) / 4) * 16
  78           </code></blockquote>
  79           <p>If it is not, an <code>INVALID_VALUE</code> error is generated.</p>
  80           </dd>
  81         </dl>
  82       </feature>
  83     </features>
  84   </overview>
  85   <idl xml:space="preserve">
  86 interface WEBGL_compressed_texture_atc {
  87     /* Compressed Texture Formats */
  88     const GLenum COMPRESSED_RGB_ATC_WEBGL                     = 0x8C92;
  89     const GLenum COMPRESSED_RGBA_ATC_EXPLICIT_ALPHA_WEBGL     = 0x8C93;
  90     const GLenum COMPRESSED_RGBA_ATC_INTERPOLATED_ALPHA_WEBGL = 0x87EE;
  91 };
  92   </idl>
  93   <history>
  94     <revision date="2012/09/11">
  95       <change>Initial revision.</change>
  96     </revision>
  97     <revision date="2013/07/03">
  98       <change>Clarified that length of ArrayBufferView is actually byteLength.</change>
  99     </revision>
 100   </history>
 101 </draft>