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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 © 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			  03/16/2013		      GLLIGHTMODEL(3G)
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