| Name |
| |
| SGIX_packed_6bytes |
| |
| Name Strings |
| |
| GL_SGIX_packed_6bytes |
| |
| Version |
| |
| $Date: 1999/04/03 08:41:01 $ $Revision: 1.3 $ |
| |
| Number |
| |
| 162 |
| |
| Dependencies |
| |
| EXT_abgr affects the definition of this extension |
| Histogram affects the definition of this extension |
| Convolution affects the definition of this extension |
| Color_table affects the definition of this extension |
| SGIS_texture4D affects the definition of this extension |
| |
| Overview |
| |
| This extension provides support for packing four component pixels |
| into a 6-byte field, where each component is represented by 12 bits. |
| Since the pixel is represented by 6 unsigned bytes it is inferred |
| that the fields or components of the pixel are not proper machine |
| types. However, since the pixel as a whole can be resepresented |
| as an integral number of bytes, the pixel storage modes, including |
| PACK_SKIP_PIXELS, PACK_ROW_LENGTH, PACK_SKIP_ROWS, PACK_IMAGE_HEIGHT_EXT, |
| PACK_SKIP_IMAGES_EXT, PACK_SWAP_BYTES, PACK_ALIGNMENT, and their unpacking |
| counterparts all work correctly. |
| |
| New Procedures and Functions |
| |
| None |
| |
| New Tokens |
| |
| Accepted by the <type> parameter of DrawPixels, ReadPixels, TexImage1D, |
| TexImage2D, GetTexImage, TexImage3D, TexSubImage1D, |
| TexSubImage2D, TexSubImage3D, GetHistogram, GetMinmax, |
| ConvolutionFilter1D, ConvolutionFilter2D, ConvolutionFilter3D, |
| GetConvolutionFilter, SeparableFilter2D, SeparableFilter3D, |
| GetSeparableFilter, ColorTable, GetColorTable, TexImage4DSGIS, |
| and TexSubImage4DSGIS: |
| |
| 6BYTES_12_12_12_12_SGIX 0x???? |
| |
| Additions to Chapter 2 of the 1.2 Specification (OpenGL Operation) |
| |
| None |
| |
| Additions to Chapter 3 of the 1.2 Specification (Rasterization) |
| |
| The token defined by this extension is added to Table 3.5: |
| |
| <type> Parameter Corresponding Special |
| Token Value GL Data Type Interpretation |
| ---------------- ------------- -------------- |
| UNSIGNED_BYTE ubyte No |
| BITMAP ubyte Yes |
| BYTE byte No |
| UNSIGNED_SHORT ushort No |
| SHORT short No |
| UNSIGNED_INT uint No |
| INT int No |
| FLOAT float No |
| BITMAP ubyte Yes |
| UNSIGNED_BYTE_3_3_2 ubyte Yes |
| UNSIGNED_BYTE_3_3_2_REV ubyte Yes |
| UNSIGNED_SHORT_5_6_5 ushort Yes |
| UNSIGNED_SHORT_5_6_5_REV ushort Yes |
| UNSIGNED_SHORT_4_4_4_4 ushort Yes |
| UNSIGNED_SHORT_4_4_4_4_REV ushort Yes |
| UNSIGNED_SHORT_5_5_5_1 ushort Yes |
| UNSIGNED_SHORT_5_5_5_1_REV ushort Yes |
| UNSIGNED_INT_8_8_8_8 uint Yes |
| UNSIGNED_INT_8_8_8_8_REV uint Yes |
| UNSIGNED_INT_10_10_10_2 uint Yes |
| UNSIGNED_INT_10_10_10_2_REV uint Yes |
| UNSIGNED_6BYTES_12_12_12_12_SGIX 6*ubyte Yes |
| |
| Table 3.5: DrawPixels and ReadPixels <type> parameter values and the |
| corresponding GL data types. Refer to table 2.2 for definitions of |
| GL data types. Special interpretations are described near the end |
| of section 3.6.4. |
| |
| [Additions to Section 3.6.4 of the GL Specification (Rasterization of Pixel |
| Rectangles) is made as follows:] |
| |
| 3.6.4 Rasterization of Pixel Rectangles |
| |
| Unpacking |
| --------- |
| [Modify fourth paragraph to read:] |
| |
| Calling DrawPixels with a <type> of UNSIGNED_BYTE_3_3_2, UNSIGNED_BYTE_3_3_2_REV, |
| UNSIGNED_SHORT_5_6_5, UNSIGNED_SHORT_5_6_5_REV, UNSIGNED_SHORT_4_4_4_4, |
| UNSIGNED_SHORT_4_4_4_4_REV, UNSIGNED_SHORT_5_5_5_1, UNSIGNED_SHORT_5_5_5_1_REV, |
| UNSIGNED_INT_8_8_8_8, UNSIGNED_INT_8_8_8_8_REV, UNSIGNED_INT_10_10_10_2, or |
| UNSIGNED_INT_10_10_10_2_REV is a special case in which all the components of |
| each group are packed into a single unsigned byte, unsigned short, or unsigned int, |
| depending on the type. Additionally, calling DrawPixels with a <type> of |
| UNSIGNED_6BYTES_12_12_12_12_SGIX is a special case in which all the components of |
| each group are is packed into 6 bytes. The number of components per packed pixel |
| is fixed by the <type>, and must match the number of components per group as |
| indicated by the <format> parameter, as listed in table 3.8. The error |
| INVALID_OPERATION is generated if a mismatch occurs. This constraint also holds |
| for all other functions that accept or return pixel data using <type> and <format> |
| parameters to define the type and format of that data. |
| |
| A new table is added to demonstrate bitfield locations <type> |
| UNSIGNED_6BYTES_12_12_12_12_SGIX. The bitfield locations for the first, second, |
| third and fourth component for this pixel type is shown in Table 3.12. |
| |
| |
| 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 |
| +--------------------------------+--------------------------------------+ |
| | | | |
| +--------------------------------+--------------------------------------+ |
| first second |
| element element |
| |
| |
| 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 |
| +--------------------------------+--------------------------------------+ |
| | | | |
| +--------------------------------+--------------------------------------+ |
| |
| third fourth |
| element element |
| |
| Table 3.12 UNSIGNED_6BYTES_12_12_12_SGIX format |
| |
| [Add to the paragraph describing byte swapping:] |
| |
| If byte swapping is enabled with UNSIGNED_6BYTES_12_12_12_SGIX as the <type>, |
| the byte swapping is performed as follows: |
| |
| given the 6byte ordering as |
| |
| b5 b4 b3 b2 b1 b0 |
| |
| where b# represents the byte index or order, then byte swapping yields |
| |
| b4 b5 b2 b3 b0 b1 |
| |
| |
| |
| |
| Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations |
| and the Framebuffer) |
| |
| [Make the following addition to Table 4.7] |
| |
| <type> GL Data Component |
| Parameter Type Conversion Formula |
| --------- ------- ------------------ |
| UNSIGNED_INT_10_10_10_2_EXT uint c = ((2**N)-1)*f |
| |
| Table 4.7: Reversed component conversions - used when component data |
| are being returned to client memory. Color, normal, and depth |
| components are converted from the internal floating-point |
| representation (f) to a datum of the specified GL data type (c) using |
| the equations in this table. All arithmetic is done in the internal |
| floating point format. These conversions apply to component data |
| returned by GL query commands and to components of pixel data returned |
| to client memory. The equations remain the same even if the |
| implemented ranges of the GL data types are greater than the minimum |
| required ranges. (Refer to table 2.2.) Equations with N as the |
| exponent are performed for each bitfield of the packed data type, |
| with N set to the number of bits in the bitfield. |
| |
| Additions to Chapter 5 of the 1.0 Specification (Special Functions) |
| |
| None |
| |
| Additions to Chapter 6 of the 1.0 Specification (State and State Requests) |
| |
| None |
| |
| Additions to the GLX Specification |
| |
| None |
| |
| GLX Protocol |
| |
| None |
| |
| Dependencies on EXT_abgr |
| |
| If EXT_abgr is not implemented, then the references to ABGR_EXT in this |
| file are invalid, and should be ignored. |
| |
| Dependencies on Histogram |
| |
| If EXT_histogram is not implemented, then the references to |
| GetHistogramEXT and GetMinmaxEXT in this file are invalid, and should be |
| ignored. |
| |
| Dependencies on Convolution |
| |
| If EXT_convolution is not implemented, then the references to |
| ConvolutionFilter1DEXT, ConvolutionFilter2DEXT, ConvolutionFilter3DEXT, |
| GetConvolutionFilterEXT, SeparableFilter2DEXT, SeparableFilter3DEXT, and |
| GetSeparableFilterEXT in this file are invalid, and should be ignored. |
| |
| Dependencies on Color_table |
| |
| If Color_table is not implemented, then the references to |
| ColorTableSGI and GetColorTableSGI in this file are invalid, and should |
| be ignored. |
| |
| Dependencies on SGIS_texture4D |
| |
| If SGIS_texture4D is not implemented, then the references to |
| TexImage4DSGIS and TexSubImage4DSGIS in this file are invalid, and should |
| be ignored. |
| |
| |
| Errors |
| |
| INVALID_OPERATION is generated by GenericPixelFunction if its <type> |
| parameter is UNSIGNED_6BYTES_12_12_12_SGIX and its |
| <format> parameter does not specify four components. |
| |
| New State |
| |
| None |
| |
| New Implementation Dependent State |
| |
| None |
