GLLIGHTMODEL(3G) UNIX Programmer's Manual GLLIGHTMODEL(3G)

glLightModelf, glLightModeli, glLightModelfv, glLightModeliv- set the lighting model parameters

voidglLightModelf( GLenumpname, GLfloatparam) voidglLightModeli( GLenumpname, GLintparam)

pnameSpecifies a single-valued lighting model parameter.GL_LIGHT_MODEL_LOCAL_VIEWER,GL_LIGHT_MODEL_COLOR_CONTROL, andGL_LIGHT_MODEL_TWO_SIDEare accepted.paramSpecifies the value thatparamwill be set to.

voidglLightModelfv( GLenumpname, const GLfloat *params) voidglLightModeliv( GLenumpname, const GLint *params)

pnameSpecifies a lighting model parameter.GL_LIGHT_MODEL_AMBIENT,GL_LIGHT_MODEL_COLOR_CONTROL,GL_LIGHT_MODEL_LOCAL_VIEWER, andGL_LIGHT_MODEL_TWO_SIDEare accepted.paramsSpecifies a pointer to the value or values thatparamswill be set to.

glLightModelsets the lighting model parameter.pnamenames a parameter andparamsgives the new value. There are three lighting model parameters:GL_LIGHT_MODEL_AMBIENTparamscontains 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 MirBSD #10-current Printed 2021-12-07 1 GLLIGHTMODEL(3G) UNIX Programmer's Manual GLLIGHTMODEL(3G) ambient scene intensity is (0.2, 0.2, 0.2, 1.0).GL_LIGHT_MODEL_COLOR_CONTROLparamsmust be eitherGL_SEPARATE_SPECULAR_COLORorGL_SINGLE_COLOR. GL_SINGLE_COLORspecifies that a single color is generated from the lighting com- putation for a vertex.GL_SEPARATE_SPECULAR_COLORspecifies 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 isGL_SINGLE_COLOR.GL_LIGHT_MODEL_LOCAL_VIEWERparamsis a single integer or floating-point value that specifies how specular reflection angles are computed. Ifparamsis 0 (or 0.0), specular reflection angles take the view direction to be parallel to and in the direction of the-zaxis, 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.GL_LIGHT_MODEL_TWO_SIDEparamsis 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. Ifparamsis 0 (or 0.0), one- sided lighting is specified, and only thefrontmaterial parameters are used in the lighting equa- tion. Otherwise, two-sided lighting is specified. In this case, vertices of back-facing polygons are lighted using thebackmaterial parameters, and have their normals reversed before the lighting equation is evaluated. Vertices of front-facing polygons are always lighted using thefrontmaterial parameters, with no change to their nor- mals. 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 MirBSD #10-current Printed 2021-12-07 2 GLLIGHTMODEL(3G) UNIX Programmer's Manual GLLIGHTMODEL(3G) dot product of the vertex's normal with the normalized vec- tor 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 toglMaterialusingGL_COLOR_INDEXES. 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.

GL_LIGHT_MODEL_COLOR_CONTROLis available only if the GL version is 1.2 or greater.

GL_INVALID_ENUMis generated ifpnameis not an accepted value.GL_INVALID_ENUMis generated ifpnameisGL_LIGHT_MODEL_COLOR_CONTROLandparamsis not one ofGL_SINGLE_COLORorGL_SEPARATE_SPECULAR_COLOR.GL_INVALID_OPERATIONis generated ifglLightModelis exe- cuted between the execution ofglBeginand the corresponding execution ofglEnd.

glGetwith argumentGL_LIGHT_MODEL_AMBIENTglGetwith argumentGL_LIGHT_MODEL_COLOR_CONTROLglGetwith argumentGL_LIGHT_MODEL_LOCAL_VIEWERglGetwith argumentGL_LIGHT_MODEL_TWO_SIDEglIsEnabledwith argumentGL_LIGHTING

glLight(3G),glMaterial(3G)MirBSD #10-current Printed 2021-12-07 3