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## GLLIGHTMODELIndex## NAMEglLightModelf, glLightModeli, glLightModelfv, glLightModeliv
- set the lighting model parameters
## C SPECIFICATIONvoid f3glLightModelffP( GLenum fIpnamefP,GLint fIparamfP ) ## PARAMETERS- f2pnamefP
- Specifies a single-valued lighting model parameter. %f3GL_LIGHT_MODEL_LOCAL_VIEWERfP, %f3GL_LIGHT_MODEL_COLOR_CONTROLfP, and %f3GL_LIGHT_MODEL_TWO_SIDEfP are accepted.
- f2paramfP
- Specifies the value that f2paramfP will be set to.
## C SPECIFICATIONvoid f3glLightModelfvfP( GLenum fIpnamefP,const GLint fI*paramsfP ) ## PARAMETERS- f2pnamefP
- Specifies a lighting model parameter. %f3GL_LIGHT_MODEL_AMBIENTfP, %f3GL_LIGHT_MODEL_COLOR_CONTROLfP, %f3GL_LIGHT_MODEL_LOCAL_VIEWERfP, and %f3GL_LIGHT_MODEL_TWO_SIDEfP are accepted.
- f2paramsfP
- Specifies a pointer to the value or values that f2paramsfP will be set to.
## DESCRIPTION%f3glLightModelfP sets the lighting model parameter. f2pnamefP names a parameter and f2paramsfP gives the new value. There are three lighting model parameters:- %f3GL_LIGHT_MODEL_AMBIENTfP
- f2paramsfP contains four integer or floating-point values that specify the ambient RGBA intensity of the entire scene. Integer values are mapped linearly such that the most positive representable value maps to 1.0, and the most negative representable value maps to -1.0. Floating-point values are mapped directly. Neither integer nor floating-point values are clamped. The initial ambient scene intensity is (0.2, 0.2, 0.2, 1.0).
- %f3GL_LIGHT_MODEL_COLOR_CONTROLfP
- f2paramsfP must be either %f3GL_SEPARATE_SPECULAR_COLORfP or %f3GL_SINGLE_COLORfP. %f3GL_SINGLE_COLORfP specifies that a single color is generated from the lighting computation for a vertex. %f3GL_SEPARATE_SPECULAR_COLORfP specifies that the specular color computation of lighting be stored separately from the remainder of the lighting computation. The specular color is summed into the generated fragment's color after the application of texture mapping (if enabled). The initial value is %f3GL_SINGLE_COLORfP.
- %f3GL_LIGHT_MODEL_LOCAL_VIEWERfP
- f2paramsfP is a single integer or floating-point value that specifies how specular reflection angles are computed. If f2paramsfP is 0 (or 0.0), specular reflection angles take the view direction to be parallel to and in the direction of the -f2zfP axis, regardless of the location of the vertex in eye coordinates. Otherwise, specular reflections are computed from the origin of the eye coordinate system. The initial value is 0.
- %f3GL_LIGHT_MODEL_TWO_SIDEfP
- f2paramsfP is a single integer or floating-point value that specifies whether one- or two-sided lighting calculations are done for polygons. It has no effect on the lighting calculations for points, lines, or bitmaps. If f2paramsfP is 0 (or 0.0), one-sided lighting is specified, and only the f2frontfP material parameters are used in the lighting equation. Otherwise, two-sided lighting is specified. In this case, vertices of back-facing polygons are lighted using the f2backfP material parameters, and have their normals reversed before the lighting equation is evaluated. Vertices of front-facing polygons are always lighted using the f2frontfP material parameters, with no change to their normals. The initial value is 0. In RGBA mode, the lighted color of a vertex is the sum of the material emission intensity, the product of the material ambient reflectance and the lighting model full-scene ambient intensity, and the contribution of each enabled light source. Each light source contributes the sum of three terms: ambient, diffuse, and specular. The ambient light source contribution is the product of the material ambient reflectance and the light's ambient intensity. The diffuse light source contribution is the product of the material diffuse reflectance, the light's diffuse intensity, and the dot product of the vertex's normal with the normalized vector from the vertex to the light source. The specular light source contribution is the product of the material specular reflectance, the light's specular intensity, and the dot product of the normalized vertex-to-eye and vertex-to-light vectors, raised to the power of the shininess of the material. All three light source contributions are attenuated equally based on the distance from the vertex to the light source and on light source direction, spread exponent, and spread cutoff angle. All dot products are replaced with 0 if they evaluate to a negative value. The alpha component of the resulting lighted color is set to the alpha value of the material diffuse reflectance. In color index mode, the value of the lighted index of a vertex ranges from the ambient to the specular values passed to %f3glMaterialfP using %f3GL_COLOR_INDEXESfP. Diffuse and specular coefficients, computed with a (.30, .59, .11) weighting of the lights' colors, the shininess of the material, and the same reflection and attenuation equations as in the RGBA case, determine how much above ambient the resulting index is.
## NOTES%f3GL_LIGHT_MODEL_COLOR_CONTROLfP is available only if the GL version is 1.2 or greater.## ERRORS%f3GL_INVALID_ENUMfP is generated if f2pnamefP is not an accepted value. %f3GL_INVALID_ENUMfP is generated if f2pnamefP is %f3GL_LIGHT_MODEL_COLOR_CONTROLfP and f2paramsfP is not one of %f3GL_SINGLE_COLORfP or %f3GL_SEPARATE_SPECULAR_COLORfP. %f3GL_INVALID_OPERATIONfP is generated if %f3glLightModelfP is executed between the execution of %f3glBeginfP and the corresponding execution of %f3glEndfP.## ASSOCIATED GETS%f3glGetfP with argument %f3GL_LIGHT_MODEL_AMBIENTfP%f3glGetfP with argument %f3GL_LIGHT_MODEL_COLOR_CONTROLfP %f3glGetfP with argument %f3GL_LIGHT_MODEL_LOCAL_VIEWERfP %f3glGetfP with argument %f3GL_LIGHT_MODEL_TWO_SIDEfP %f3glIsEnabledfP with argument %f3GL_LIGHTINGfP ## SEE ALSO%f3glLight(3G)fP, %f3glMaterial(3G)fP
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