| XXX - Not complete yet!!! |
| |
| Name |
| |
| EXT_index_func |
| |
| Name Strings |
| |
| GL_EXT_index_func |
| |
| Version |
| |
| $Date: 1996/11/21 00:52:23 $ $Revision: 1.3 $ |
| |
| Number |
| |
| 95 |
| |
| Dependencies |
| |
| None |
| |
| Overview |
| |
| This extension provides a way to discard fragments when a comparison |
| between the fragment's index value and a reference index fails. This |
| may be used similarly to the alpha test which is available in RGBA mode. |
| |
| New Procedures and Functions |
| |
| void IndexFuncEXT (enum func, float ref) |
| |
| New Tokens |
| |
| Accepted by the <cap> parameter of Enable, Disable, and IsEnabled, |
| and by the <pname> parameter of GetBooleanv, GetIntegerv, GetFloatv, |
| and GetDoublev: |
| |
| INDEX_TEST_EXT |
| |
| Accepted by the <pname> parameter of GetBooleanv, GetIntegerv, |
| GetFloatv, and GetDoublev: |
| |
| INDEX_TEST_FUNC_EXT |
| INDEX_TEST_REF_EXT |
| |
| Additions to Chapter 2 of the 1.1 Specification (OpenGL Operation) |
| |
| None |
| |
| Additions to Chapter 3 of the 1.1 Specification (Rasterization) |
| |
| None |
| |
| Additions to Chapter 4 of the 1.1 Specification (Per-Fragment Operations |
| and the Frame Buffer) |
| |
| A new section is added immediately following section 4.1.3 Alpha Test. |
| |
| Index Test |
| |
| This step applies only to color index mode. The index test discards |
| a fragment conditional on the outcome of a comparison between the |
| incoming fragment's index value and a constant reference value. The |
| comparison is enabled or disabled with the generic Enable and Disable |
| commands using the symbolic constant INDEX_TEST_EXT. When disabled, |
| it is as if the comparison always passes. The test is controlled with |
| |
| void IndexFunc (enum func, float ref); |
| |
| <func> is a symbolic constant indicating the index test function; <ref> |
| is a reference value. <ref> is converted to a fixed-point value |
| according to the rules given for a color index in section 2.13.9. For |
| purposes of the index test, the fragment's index value is also rounded |
| to the nearest integer representable in the color index portion of the |
| framebuffer. The possible constants specifying the test function are |
| NEVER, ALWAYS, LESS, LEQUAL, EQUAL, GEQUAL, GREATER, or NOTEQUAL, |
| meaning pass the fragment never, always, if the fragment's index value |
| is less than, less than or equal to, equal to, greater than, or not |
| equal to the reference value, respectively. |
| |
| Additions to Chapter 5 of the 1.1 Specification (Special Functions) |
| |
| None |
| |
| Additions to Chapter 6 of the 1.1 Specification (State and State Requests) |
| |
| None |
| |
| Additions to the GLX Specification |
| |
| XXX - Not complete yet!!! |
| |
| GLX Protocol |
| |
| XXX - Not complete yet!!! |
| |
| Errors |
| |
| INVALID_ENUM is generated if the <func> parameter of IndexFuncEXT |
| is not one of NEVER, ALWAYS, LESS, LEQUAL, EQUAL, GEQUAL, GREATER, or |
| NOTEQUAL. |
| |
| INVALID_OPERATION is generated if IndexFuncEXT is called between |
| execution of Begin and corresponding execution of End. |
| |
| New State |
| Initial |
| Get Value Get Command Type Value Attrib |
| --------- ----------- ---- ------- ------ |
| |
| INDEX_TEST_EXT IsEnabled B False color-buffer/enable |
| INDEX_TEST_FUNC_EXT GetFloatv Z8 ALWAYS color-buffer |
| INDEX_TEST_REF_EXT GetFloatv R 0 color-buffer |
| |
| New Implementation Dependent State |
| |
| None |
