| Name |
| |
| SGIX_fog_blend_alpha |
| SGIX_fog_blend_color |
| |
| Name Strings |
| |
| GL_SGIX_fog_blend |
| |
| Version |
| |
| $Date: 1997/09/15 19:26:36 $ $Revision: 1.3 $ |
| |
| Number |
| |
| ???? |
| |
| Dependencies |
| |
| XXX |
| |
| Overview |
| |
| This extension affect the way the fog coefficient (f) is used to |
| blend the rasterized fragments in non-indexed color mode. |
| When enabled using the GL_FOG_BLEND_ALPHA_SGIX parameter, |
| the alpha component of the fog color is used to change the |
| resulting alpha, as well as the RGB components. |
| The color components may stay unchanged by the fog computation |
| if the GL_FOG_BLEND_COLOR_SGIX is disabled. |
| No change is done to the equation C = f*Cr + (1-f)Cf |
| |
| |
| New Procedures and Functions |
| |
| None |
| |
| New Tokens |
| |
| Accepted by the <cap> parameter of Enable, Disable, and IsEnabled |
| |
| GL_FOG_BLEND_ALPHA_SGIX 0x81FE |
| GL_FOG_BLEND_COLOR_SGIX 0x81FF |
| |
| Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation) |
| |
| None |
| |
| Additions to Chapter 3 of the 1.0 Specification (Rasterization) |
| |
| |
| 3.9 Fog |
| |
| ... (The rasterized fragment's A value is not changed by fog blending.)... |
| is removed and replaced by. |
| |
| The rasterized fragment alpha value is not changed by the fog blending, |
| unless specified otherwise by enabling it with the GL_FOG_BLEND_ALPHA_SGIX |
| parameter. Color modifications can be turned off by disabling with |
| the GL_FOG_BLEND_COLOR_SGIX paramater. |
| |
| |
| |
| Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations |
| and the Framebuffer) |
| |
| None |
| |
| 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) |
| |
| Fog alpha blend enable/disable state is checked by calling glIsEnable |
| function with GL_FOG_BLEND_ALPHA_SGIX parameter. |
| Fog color blend enable/disable state is checked by calling glIsEnable |
| function with GL_FOG_BLEND_COLOR_SGIX parameter. |
| |
| When PushAttrib is called with FOG_BIT enabled, the state of the |
| fog color and alpha blend is pushed. When an attribute set |
| that includes enable information is popped, the state of the fog |
| color and alpha blend is restored to the pushed value. |
| |
| Additions to the GLX Specification |
| |
| None |
| |
| Errors |
| |
| None |
| |
| New State |
| |
| Get Value Get Command Type Initial Value Attribute |
| --------- ----------- ---- ------------- --------- |
| FOG_BLEND_ALPHA_SGIX IsEnabled B FALSE fog |
| FOG_BLEND_COLOR_SGIX IsEnabled B TRUE fog |
| |
| |
| New Implementation Dependent State |
| |
| None |
| |