| Name |
| |
| SGIS_sharpen_texture |
| |
| Name Strings |
| |
| GL_SGIS_sharpen_texture |
| |
| Version |
| |
| $Date: 1995/07/09 06:48:51 $ $Revision: 1.16 $ |
| |
| Number |
| |
| 22 |
| |
| Dependencies |
| |
| EXT_texture is required |
| EXT_texture3D affects the definition of this extension |
| EXT_texture_object affects the definition of this extension |
| |
| Overview |
| |
| This extension introduces texture magnification filters that sharpen |
| the resulting image by extrapolating from the level 1 image to the |
| level 0 image. Sharpening can be enabled for all color channels, for |
| the alpha channel only, or for the red, green, and blue channels only. |
| |
| New Procedures and Functions |
| |
| void SharpenTexFuncSGIS(enum target, |
| sizei n, |
| const float* points); |
| |
| void GetSharpenTexFuncSGIS(enum target, |
| float* points); |
| |
| New Tokens |
| |
| Accepted by the <param> parameter of TexParameteri and TexParameterf, |
| and by the <params> parameter of TexParameteriv and TexParameterfv, when |
| their <pname> parameter is TEXTURE_MAG_FILTER: |
| |
| LINEAR_SHARPEN_SGIS |
| LINEAR_SHARPEN_ALPHA_SGIS |
| LINEAR_SHARPEN_COLOR_SGIS |
| |
| Accepted by the <pname> parameter of GetTexParameteriv and |
| GetTexParameterfv: |
| |
| SHARPEN_TEXTURE_FUNC_POINTS_SGIS |
| |
| Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation) |
| |
| None |
| |
| Additions to Chapter 3 of the 1.0 Specification (Rasterization) |
| |
| GL Specification Table 3.7 is updated as follows: |
| |
| Name Type Legal Values |
| ---- ---- ------------ |
| TEXTURE_WRAP_S integer CLAMP, REPEAT |
| TEXTURE_WRAP_T integer CLAMP, REPEAT |
| TEXTURE_WRAP_R_EXT integer CLAMP, REPEAT |
| TEXTURE_MIN_FILTER integer NEAREST, LINEAR, |
| NEAREST_MIPMAP_NEAREST, |
| NEAREST_MIPMAP_LINEAR, |
| LINEAR_MIPMAP_NEAREST, |
| LINEAR_MIPMAP_LINEAR, |
| FILTER4_SGIS |
| TEXTURE_MAG_FILTER integer NEAREST, LINEAR, |
| FILTER4_SGIS, |
| LINEAR_DETAIL_SGIS, |
| LINEAR_DETAIL_ALPHA_SGIS, |
| LINEAR_DETAIL_COLOR_SGIS, |
| LINEAR_SHARPEN_SGIS, |
| LINEAR_SHARPEN_ALPHA_SGIS, |
| LINEAR_SHARPEN_COLOR_SGIS |
| TEXTURE_BORDER_COLOR 4 floats any 4 values in [0,1] |
| DETAIL_TEXTURE_LEVEL_SGIS integer any non-negative integer |
| DETAIL_TEXTURE_MODE_SGIS integer ADD, MODULATE |
| |
| Table 3.7: Texture parameters and their values. |
| |
| 3.8.2.2 Texture magnification with sharpening |
| |
| Three additional texture magnification filters are defined for texture |
| magnification. These values, which are assigned to TEXTURE_MAG_FILTER, |
| are LINEAR_SHARPEN_SGIS, LINEAR_SHARPEN_ALPHA_SGIS, and |
| LINEAR_SHARPEN_COLOR_SGIS. All three filters sample the level 0 |
| texture array exactly as it would be sampled with filter mode LINEAR. |
| If texture levels 0 and 1 are "complete", as described in the Mipmapping |
| portion of Section 3.8.1 (Texture Minification) of the GL Specification, |
| the level 1 array of the texture is also linearly sampled, just as though |
| mipmap minification was being performed with LOD (the level of detail |
| parameter) valued near 1.0. If levels 0 and 1 are not complete, it is |
| as though the magnification texture filter was LINEAR. (Although |
| querying the magnification filter value will return the value as |
| specified.) |
| |
| The texture value computed from the level 0 array (T0) and the |
| value computed from the level one array (T1) are combined to compute |
| the final texture value (T): |
| |
| T' = ((1 + F(LOD)) * T0) - (F(LOD) * T1) |
| |
| / 0 T' < 0 |
| T = < T' 0 <= T' <= 1 |
| \ 1 T' > 1 |
| |
| F is a function of the level-of-detail parameter LOD, which is |
| represented by the Greek character lambda in the GL Specification. |
| |
| The function F of level-of-detail parameter LOD is specified by |
| calling SharpenTexFuncSGIS with <target> set to TEXTURE_1D, TEXTURE_2D, |
| or TEXTURE_3D_EXT, <points> pointing at an array of pairs of floating |
| point values, and <n> set to the number of value pairs in <points>. The |
| first value of each value pair in <points> specifies a value of LOD, and |
| the second value of each value pair specifies the corresponding function |
| value. The order in which the points are specified is not significant. |
| The <n> value pairs in <points> completely specify the function, |
| replacing any previous specification that may have existed. Since |
| negative values of LOD correspond to magnification and positive values |
| correspond to minification, the points should have negative values for |
| LOD (though it is not an error to specify positive values). |
| |
| Function F is evaluated by sorting the value pairs specified by |
| SharpenTexFuncSGIS by LOD value, then fitting a curve through these |
| points. This curve may be linear between adjacent points, or it may be |
| smoothed, but it will pass exactly through the points, limited only by |
| the resolution of the implementation. The value pair with the lowest |
| LOD value specifies the function value F for all values of LOD less than |
| or equal to that pair's LOD. Likewise, the value pair with the greatest |
| LOD value specifies the function value F for all values of LOD greater |
| than or equal to that pair's LOD. F is undefined if two or more value |
| pairs have the same LOD value. |
| |
| If the texture magnification filter is LINEAR_SHARPEN_SGIS, then both |
| the color and the alpha components of T are computed as described |
| in the equations above. If the filter is LINEAR_SHARPEN_COLOR_SGIS, |
| then all components of T other than alpha are computed as described |
| above, and the alpha component of T is computed as if the texture |
| magnification filter were LINEAR. Finally, if the filter is |
| LINEAR_SHARPEN_ALPHA_SGIS, the alpha component of T is computed as |
| described in the equations above, and all other components of T |
| are computed as if the texture magnification filter were LINEAR. |
| |
| Minification vs. Magnification |
| ------------------------------ |
| |
| If the magnification filter is given by LINEAR_SHARPEN_SGIS, |
| LINEAR_SHARPEN_ALPHA_SGIS, or LINEAR_SHARPEN_COLOR_SGIS, and the |
| minification filter is given by NEAREST_MIPMAP_NEAREST or |
| LINEAR_MIPMAP_NEAREST, then c = 0.5. The parameter c is used to |
| determine whether minification or magnification filtering is done, |
| as described in Section 3.8.2 of the GL Specification (Texture |
| Magnification). |
| |
| 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) |
| |
| GetSharpenTexFuncSGIS is not included in display lists. |
| |
| Additions to Chapter 6 of the 1.0 Specification (State and State Requests) |
| |
| The number of points in the sharpen texture function specification of |
| a texture is queried by calling GetTexParameteriv or GetTexParameterfv |
| with <target> set to the target of the desired texture and <pname> set |
| to SHARPEN_TEXTURE_FUNC_POINTS_SGIS. The function |
| GetSharpenTexFuncSGIS returns in <points> all of the points in the |
| sharpen texture function of texture <target>. |
| |
| Additions to the GLX Specification |
| |
| None |
| |
| GLX Protocol |
| |
| Two new GLX protocol commands are added. |
| |
| SharpenTexFuncSGIS |
| 2 12+4*2*n rendering command length |
| 2 2052 rendering command opcode |
| 4 ENUM target |
| 4 INT32 n |
| 4*2*n LISTofFLOAT points |
| |
| GetSharpenTexFuncSGIS |
| 1 CARD8 opcode (X assigned) |
| 1 17 GLX opcode (glXVendorPrivateWithReply) |
| 2 4 request length |
| 4 4097 vendor specific opcode |
| 4 GLX_CONTEXT_TAG context tag |
| 4 ENUM target |
| => |
| 1 1 reply |
| 1 unused |
| 2 CARD16 sequence number |
| 4 n reply length, m = n |
| 4 unused |
| 4 CARD32 n |
| 16 unused |
| n*4 LISTofFLOAT32 points |
| |
| Note that n may be zero, indicating that a GL error occurred. |
| Other n must be even and n >= 2. |
| |
| Dependencies on EXT_texture |
| |
| EXT_texture is required. |
| |
| Dependencies on EXT_texture3D |
| |
| If EXT_texture3D is not implemented, references in this specification |
| to TEXTURE_3D_EXT are invalid, and should be ignored. |
| |
| Dependencies on EXT_texture_object |
| |
| If EXT_texture_object is implemented, the state values named |
| |
| SHARPEN_TEXTURE_FUNC_POINTS_SGIS |
| <SHARPEN_TEXTURE_FUNC> |
| |
| are added to the state vector of each texture object. When an attribute |
| set that includes texture information is popped, the bindings and |
| enables are first restored to their pushed values, then the bound |
| textures have their sharpen parameters restored to their pushed values. |
| |
| Errors |
| |
| INVALID_ENUM is generated if SharpenTexFuncSGIS or |
| GetSharpenTexFuncSGIS parameter <target> is not TEXTURE_1D, TEXTURE_2D, |
| or TEXTURE_3D_EXT. |
| |
| INVALID_VALUE is generated if SharpenTexFuncSGIS parameter <n> is |
| negative. |
| |
| INVALID_OPERATION is generated if SharpenTexFuncSGIS or |
| GetSharpenTexFuncSGIS is executed between execution of Begin and the |
| corresponding execution to End. |
| |
| New State |
| |
| Get Value Get Command Type Initial Value Attribute |
| --------- ----------- ---- ------------- --------- |
| SHARPEN_TEXTURE_FUNC_POINTS_SGIS GetTexParameteriv n x Z+ 2 texture |
| <SHARPEN_TEXTURE_FUNC> GetSharpenTexFuncSGIS n x m x R {0, 0}, {-4, 1} texture |
| |
| New Implementation Dependent State |
| |
| None |
