| 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 |
