kc3-lang/angle/extensions/ANGLE_lossy_etc_decode.txt

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• Hash : e3939b98
  Author :
  Date : 2015-12-01T15:36:51
  

  D3D11: Transcode ETC1 to BC1.
  
  Adds a new extension to allow transcode ETC formats to suitable BC formats.
  This commit implements ETC1 to BC1. More formats will be supported soon.
  
  BUG=angleproject:1285
  
  Change-Id: Iacbfbc2248dfe1aebf24b92696249a9404e331cd
  Reviewed-on: https://chromium-review.googlesource.com/316511
  Reviewed-by: Corentin Wallez <cwallez@chromium.org>
  Commit-Queue: Corentin Wallez <cwallez@chromium.org>
  

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• extensions/ANGLE_lossy_etc_decode.txt

• Name
  
      ANGLE_lossy_etc_decode
  
  Name Strings
  
      GL_ANGLE_lossy_etc_decode
  
  Contributors
  
      Minmin Gong  (mgong 'at' microsoft.com)
  
  Contacts
  
      Minmin Gong  (mgong 'at' microsoft.com)
  
  Status
  
      Draft
  
  Version
  
      Last Modified Date: Nov 25, 2015
      Author Revision: 1
  
  Number
  
      TBD
  
  Dependencies
  
      Requires OpenGL ES 3.0 for ETC2 and EAC formats, or OpenGL ES 2.0 and
      OES_compressed_ETC1_RGB8_texture for ETC1 format.
      The extension is written against the OpenGL ES 2.0 specification.
  
  Overview
  
      Both the OpenGL ES 3.0 specification and OES_compressed_ETC1_RGB8_texture
      specify that Ericsson Texture Compression (ETC) decoding must not be lossy.
      The goal of this extension is to allow a lossy decode of
      compressed textures in the ETC formats in OpenGL ES, for lower memory
      and bandwidth consumption.
  
      This extension uses the same ETC compression format as OpenGL ES 3.0
      and OES_compressed_ETC1_RGB8_texture, with the restriction that the texture
      dimensions must be a multiple of four (except for mip levels where the
      dimensions are either 2 or 1). And the requirement that ETC decoding must
      not be lossy is relaxed.
  
      See OES_compressed_ETC1_RGB8_texture for a description of the ETC1 format.
      Also see OpenGL ES 3.0 specification appendix C.2 (ETC Compressed Texture
      ImageFormats) for a description of ETC2 and EAC formats.
  
  IP Status
  
      See Ericsson's "IP Statement"
  
  New Procedures and Functions
  
      None.
  
  New Types
  
      None.
  
  New Tokens
  
      Accepted by the <internalformat> parameter of CompressedTexImage2D
      and the <format> parameter of CompressedTexSubImage2D:
  
      ETC1_RGB8_LOSSY_DECODE_ANGLE                                  0x9690
      COMPRESSED_R11_LOSSY_DECODE_EAC_ANGLE                         0x9691
      COMPRESSED_SIGNED_R11_LOSSY_DECODE_EAC_ANGLE                  0x9692
      COMPRESSED_RG11_LOSSY_DECODE_EAC_ANGLE                        0x9693
      COMPRESSED_SIGNED_RG11_LOSSY_DECODE_EAC_ANGLE                 0x9694
      COMPRESSED_RGB8_LOSSY_DECODE_ETC2_ANGLE                       0x9695
      COMPRESSED_SRGB8_LOSSY_DECODE_ETC2_ANGLE                      0x9696
      COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_LOSSY_DECODE_ETC2_ANGLE   0x9697
      COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_LOSSY_DECODE_ETC2_ANGLE  0x9698
      COMPRESSED_RGBA8_LOSSY_DECODE_ETC2_EAC_ANGLE                  0x9699
      COMPRESSED_SRGB8_ALPHA8_LOSSY_DECODE_ETC2_EAC_ANGLE           0x969A
  
  Additions to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization)
  
      Add the following to Section 3.7.3 (Compressed Texture Images)
      (at the end of the description of the CompressedTexImage2D command):
  
      Compressed Internal Format                                    Base Internal Format
      ==========================                                    ====================
      ETC1_RGB8_LOSSY_DECODE_ANGLE                                  RGB
      COMPRESSED_R11_LOSSY_DECODE_EAC_ANGLE                         R
      COMPRESSED_SIGNED_R11_LOSSY_DECODE_EAC_ANGLE                  R
      COMPRESSED_RG11_LOSSY_DECODE_EAC_ANGLE                        RG
      COMPRESSED_SIGNED_RG11_LOSSY_DECODE_EAC_ANGLE                 RG
      COMPRESSED_RGB8_LOSSY_DECODE_ETC2_ANGLE                       RGB
      COMPRESSED_SRGB8_LOSSY_DECODE_ETC2_ANGLE                      RGB
      COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_LOSSY_DECODE_ETC2_ANGLE   RGBA
      COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_LOSSY_DECODE_ETC2_ANGLE  RGBA
      COMPRESSED_RGBA8_LOSSY_DECODE_ETC2_EAC_ANGLE                  RGBA
      COMPRESSED_SRGB8_ALPHA8_LOSSY_DECODE_ETC2_EAC_ANGLE           RGBA
  
      Table 3.x: Specific Compressed Internal Formats
  
      If <internalformat> is one of the ETC lossy decode formats listed in
      Table 3.x, the compressed texture is stored in an unspecified compressed
      texture format, that may introduce losses of precision in the texture data.
      The GL and the ETC texture compression algorithm support only 2D images
      without borders.
  
      CompressedTexImage2D will produce the INVALID_OPERATION error when
      <internalformat> is one of the lossy decode ETC-format values from
      Table 3.x under the following conditions:
  
        * <border> is non-zero.
        * <width> is not one, two, nor a multiple of four.
        * <height> is not one, two, nor a multiple of four.
  
      Add the following to Section 3.7.3 (Compressed Texture Images)
      (at the end of the description of the CompressedTexSubImage2D command):
  
      If the internal format of the texture image being modified is an ETC-format
      listed in Table 3.x, the compressed texture is stored in an unspecified
      compressed texture format. The xoffset and yoffset must also be aligned to
      4x4 texel block boundaries, since ETC encoding makes it difficult to modify
      non-aligned regions. CompressedTexSubImage2D will result in an
      INVALID_OPERATION error only if one of the following conditions occurs:
  
        * <width> is not a multiple of four nor equal to TEXTURE_WIDTH.
        * <height> is not a multiple of four nor equal to TEXTURE_HEIGHT.
        * <xoffset> or <yoffset> is not a multiple of four.
        * <format> does not match the internal format of the texture image
          being modified.
  
  Errors
  
      INVALID_OPERATION is generated by CompressedTexImage2D if
      lossy decode ETC-format is used and <internalformat> is one of the
      compressed internal formats from Table 3.x and any of the following apply:
        - <border> is not equal to zero.
        - <width> is not one, two, nor a multiple of four.
        - <height> is not one, two, nor a multiple of four.
  
      INVALID_OPERATION is generated by CompressedTexSubImage2D if
      lossy decode ETC-format is used and <format> is one of the compressed
      interal formats from Table 3.x and any of the following apply:
        - <width> is not a multiple of four nor equal to TEXTURE_WIDTH;
        - <height> is not a multiple of four nor equal to TEXTURE_HEIGHT;
        - <xoffset> or <yoffset> is not a multiple of four;
        - <format> does not match the internal format of the texture image
        being modified.
  
  New State
  
      None.
  
  Revision History
  
      Revision 1, 2015/11/25 - mgong
        - Initial revision
  

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