| Name |
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| OES_texture_env_crossbar |
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| Name Strings |
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| GL_OES_texture_env_crossbar |
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| Contact |
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| Notice |
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| Copyright (c) 2005-2013 The Khronos Group Inc. Copyright terms at |
| http://www.khronos.org/registry/speccopyright.html |
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| Status |
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| Version |
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| Last modified date: May 18, 2005 |
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| Number |
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| OpenGL ES Extension #21 |
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| Dependencies |
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| OpenGL ES 1.1 is required. |
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| This extension is based on the ARB_texture_env_crossbar |
| extension specification. |
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| Overview |
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| This extension adds the capability to use the texture color from |
| other texture units as sources to the COMBINE enviornment |
| function. OpenGL ES 1.1 defined texture combine functions which |
| could use the color from the current texture unit as a source. |
| This extension adds the ability to use the color from any texture |
| unit as a source. |
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| Issues |
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| Please refer to the ARB_texture_env_crossbar extension specification. |
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| New Procedures and Functions |
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| None |
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| New Tokens |
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| Accepted by the <params> parameter of TexEnvf, TexEnvi, TexEnvfv, |
| and TexEnviv when the <pname> parameter value is SOURCE0_RGB, |
| SOURCE1_RGB, SOURCE2_RGB, SOURCE0_ALPHA, |
| SOURCE1_ALPHA, or SOURCE2_ALPHA |
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| TEXTURE<n> 0x84C0+<n> |
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| where <n> is in the range 0 to MAX_TEXTURE_UNITS. |
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| Additions to Chapter 2 of the GL Specification (OpenGL Operation) |
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| None |
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| Additions to Chapter 3 of the GL Specification (Rasterization) |
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| The arguments Arg0, Arg1 and Arg2 are determined by the values of |
| SOURCE<n>_RGB, SOURCE<n>_ALPHA, OPERAND<n>_RGB and |
| OPERAND<n>_ALPHA. In the following two tables, Ct and At are |
| the filtered texture RGB and alpha values; Ct<n> and At<n> are the |
| filtered texture RGB and alpha values from the texture bound to |
| texture unit <n>; Cc and Ac are the texture environment RGB and |
| alpha values; Cf and Af are the RGB and alpha of the primary color |
| of the incoming fragment; and Cp and Ap are the RGB and alpha |
| values resulting from the previous texture environment. On texture |
| environment 0, Cp and Ap are identical to Cf and Af, respectively. |
| The relationship is described in table 3.5 and 3.6 of the OpenGL ES 1.2 |
| specification. |
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| Added to table 3.5 of the OpenGL ES 1.2 specification: |
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| SOURCE<n>_RGB OPERAND<n>_RGB Argument |
| ------------- -------------- -------- |
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| TEXTURE<n> SRC_COLOR Ct<n> |
| ONE_MINUS_SRC_COLOR (1-Ct<n>) |
| SRC_ALPHA At<n> |
| ONE_MINUS_SRC_ALPHA (1-At<n>) |
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| Table 3.6: COMBINE_RGB texture functions |
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| Added to table 3.6 of the OpenGL ES 1.2 specification: |
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| SOURCE<n>_ALPHA OPERAND<n>_ALPHA Argument |
| --------------- ---------------- -------- |
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| TEXTURE<n> SRC_ALPHA At<n> |
| ONE_MINUS_SRC_ALPHA (1-At<n>) |
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| Table 3.6: COMBINE_ALPHA texture functions |
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| Additions to Chapter 4 of the GL Specification (Per-Fragment Operations |
| and the Framebuffer) |
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| None |
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| Additions to Chapter 5 of the GL Specification (Special Functions) |
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| None |
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| Additions to Chapter 6 of the GL Specification (State and State Requests) |
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| None |
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| Additions to Appendix F of the GL Specification (ARB Extensions) |
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| Inserted after the second paragraph of F.2.12: |
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| If the value of TEXTURE_ENV_MODE is COMBINE, the texture |
| function associated with a given texture unit is computed using |
| the values specified by SOURCE<n>_RGB, SOURCE<n>_ALPHA, |
| OPERAND<n>_RGB and OPERAND<n>_ALPHA. If TEXTURE<n> is |
| specified as SOURCE<n>_RGB or SOURCE<n>_ALPHA, the texture |
| value from texture unit <n> will be used in computing the texture |
| function for this texture unit. |
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| Inserted after the third paragraph of F.2.12: |
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| If a texture environment for a given texture unit references a |
| texture unit that is disabled or does not have a valid texture |
| object bound to it, then it is as if texture blending is disabled |
| for the given texture unit. Every texture unit implicitly |
| references the texture object that is bound to it, regardless |
| of the texture function specified by COMBINE_RGB or COMBINE_ALPHA. |
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| Additions to the GLX Specification |
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| None |
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| GLX Protocol |
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| None |
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| Errors |
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| INVALID_ENUM is generated if <params> value for SOURCE0_RGB, |
| SOURCE1_RGB, SOURCE2_RGB, SOURCE0_ALPHA, |
| SOURCE1_ALPHA or SOURCE2_ALPHA is not one of TEXTURE, |
| CONSTANT, PRIMARY_COLOR, PREVIOUS, or TEXTURE<n>, |
| where <n> is in the range 0 to MAX_TEXTURE_UNITS. |
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| New State |
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| None |