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GLLIGHTMODEL(3G)			  OpenGL Manual 			 GLLIGHTMODEL(3G)

NAME
       glLightModel - set the lighting model parameters

C SPECIFICATION
       void glLightModelf(GLenum pname, GLfloat param);

       void glLightModeli(GLenum pname, GLint param);

PARAMETERS
       pname
	   Specifies a single-valued lighting model parameter.	GL_LIGHT_MODEL_LOCAL_VIEWER,
	   GL_LIGHT_MODEL_COLOR_CONTROL, and GL_LIGHT_MODEL_TWO_SIDE are accepted.

       param
	   Specifies the value that param will be set to.

C SPECIFICATION
       void glLightModelfv(GLenum pname, const GLfloat * params);

       void glLightModeliv(GLenum pname, const GLint * params);

PARAMETERS
       pname
	   Specifies a lighting model parameter.  GL_LIGHT_MODEL_AMBIENT,
	   GL_LIGHT_MODEL_COLOR_CONTROL, GL_LIGHT_MODEL_LOCAL_VIEWER, and GL_LIGHT_MODEL_TWO_SIDE
	   are accepted.

       params
	   Specifies a pointer to the value or values that params will be set to.

DESCRIPTION
       glLightModel sets the lighting model parameter.	pname names a parameter and params gives
       the new value. There are three lighting model parameters:

       GL_LIGHT_MODEL_AMBIENT

	   params 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).

       GL_LIGHT_MODEL_COLOR_CONTROL

	   params must be either GL_SEPARATE_SPECULAR_COLOR or GL_SINGLE_COLOR.  GL_SINGLE_COLOR
	   specifies that a single color is generated from the lighting computation for a vertex.
	   GL_SEPARATE_SPECULAR_COLOR 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 GL_SINGLE_COLOR.

       GL_LIGHT_MODEL_LOCAL_VIEWER

	   params is a single integer or floating-point value that specifies how specular
	   reflection angles are computed. If params is 0 (or 0.0), specular reflection angles
	   take the view direction to be parallel to and in the direction of the -z 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.

       GL_LIGHT_MODEL_TWO_SIDE

	   params 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 params is 0 (or 0.0),
	   one-sided lighting is specified, and only the front 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 back material parameters and
	   have their normals reversed before the lighting equation is evaluated. Vertices of
	   front-facing polygons are always lighted using the front 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 glMaterial() using GL_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.

NOTES
       GL_LIGHT_MODEL_COLOR_CONTROL is available only if the GL version is 1.2 or greater.

ERRORS
       GL_INVALID_ENUM is generated if pname is not an accepted value.

       GL_INVALID_ENUM is generated if pname is GL_LIGHT_MODEL_COLOR_CONTROL and params is not
       one of GL_SINGLE_COLOR or GL_SEPARATE_SPECULAR_COLOR.

       GL_INVALID_OPERATION is generated if glLightModel is executed between the execution of
       glBegin() and the corresponding execution of glEnd().

ASSOCIATED GETS
       glGet() with argument GL_LIGHT_MODEL_AMBIENT

       glGet() with argument GL_LIGHT_MODEL_COLOR_CONTROL

       glGet() with argument GL_LIGHT_MODEL_LOCAL_VIEWER

       glGet() with argument GL_LIGHT_MODEL_TWO_SIDE

       glIsEnabled() with argument GL_LIGHTING

SEE ALSO
       glLight(), glMaterial()

COPYRIGHT
       Copyright (C) 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI
       Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.

AUTHORS
       opengl.org

opengl.org				    06/10/2014				 GLLIGHTMODEL(3G)
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