glMaterial.3gl

Name

  glMaterialf, glMateriali, glMaterialfv, glMaterialiv - specify material
  parameters for the lighting model

C Specification

  void glMaterialf( GLenum face,
		    GLenum pname,
		    GLfloat param )
  void glMateriali( GLenum face,
		    GLenum pname,
		    GLint param	)

Parameters

  face	  Specifies which face or faces	are being updated.  Must be one	of
	  GL_FRONT, GL_BACK, or	GL_FRONT_AND_BACK.

  pname	  Specifies the	single-valued material parameter of the	face or	faces
	  that is being	updated.  Must be GL_SHININESS.

  param	  Specifies the	value that parameter GL_SHININESS will be set to.

C Specification

  void glMaterialfv( GLenum face,
		     GLenum pname,
		     const GLfloat *params )
  void glMaterialiv( GLenum face,
		     GLenum pname,
		     const GLint *params )

Parameters

  face Specifies which face or faces are being updated.	 Must be one of
       GL_FRONT, GL_BACK, or GL_FRONT_AND_BACK.

  pname
       Specifies the material parameter	of the face or faces that is being
       updated.	 Must be one of	GL_AMBIENT, GL_DIFFUSE,	GL_SPECULAR,
       GL_EMISSION, GL_SHININESS, GL_AMBIENT_AND_DIFFUSE,  or
       GL_COLOR_INDEXES.

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

Description

  glMaterial assigns values to material	parameters.  There are two matched
  sets of material parameters.	One, the front-facing set, is used to shade
  points, lines, bitmaps, and all polygons (when two-sided lighting is
  disabled), or	just front-facing polygons (when two-sided lighting is
  enabled).  The other set, back-facing, is used to shade back-facing
  polygons only	when two-sided lighting	is enabled.  Refer to the
  glLightModel reference page for details concerning one- and two-sided
  lighting calculations.


  glMaterial takes three arguments.  The first,	face, specifies	whether	the
  GL_FRONT materials, the GL_BACK materials, or	both GL_FRONT_AND_BACK
  materials will be modified.  The second, pname, specifies which of several
  parameters in	one or both sets will be modified.  The	third, params,
  specifies what value or values will be assigned to the specified parameter.

  Material parameters are used in the lighting equation	that is	optionally
  applied to each vertex.  The equation	is discussed in	the glLightModel
  reference page.  The parameters that can be specified	using glMaterial, and
  their	interpretations	by the lighting	equation, are as follows:

  GL_AMBIENT	      params contains four integer or floating-point values
		      that specify the ambient RGBA reflectance	of the
		      material.	 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
		      default ambient reflectance for both front- and back-
		      facing materials is (0.2,	0.2, 0.2, 1.0).

  GL_DIFFUSE	      params contains four integer or floating-point values
		      that specify the diffuse RGBA reflectance	of the
		      material.	 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
		      default diffuse reflectance for both front- and back-
		      facing materials is (0.8,	0.8, 0.8, 1.0).

  GL_SPECULAR	      params contains four integer or floating-point values
		      that specify the specular	RGBA reflectance of the
		      material.	 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
		      default specular reflectance for both front- and back-
		      facing materials is (0.0,	0.0, 0.0, 1.0).

  GL_EMISSION	      params contains four integer or floating-point values
		      that specify the RGBA emitted light intensity of the
		      material.	 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
		      default emission intensity for both front- and back-
		      facing materials is (0.0,	0.0, 0.0, 1.0).

  GL_SHININESS	      params is	a single integer or floating-point value that
		      specifies	the RGBA specular exponent of the material.
		      Integer and floating-point values	are mapped directly.
		      Only values in the range [0,128] are accepted.  The
		      default specular exponent	for both front-	and back-
		      facing materials is 0.

  GL_AMBIENT_AND_DIFFUSE
		      Equivalent to calling glMaterial twice with the same
		      parameter	values,	once with GL_AMBIENT and once with
		      GL_DIFFUSE.

  GL_COLOR_INDEXES    params contains three integer or floating-point values
		      specifying the color indices for ambient,	diffuse, and
		      specular lighting.  These	three values, and
		      GL_SHININESS, are	the only material values used by the
		      color index mode lighting	equation.  Refer to the
		      glLightModel reference page for a	discussion of color
		      index lighting.

Notes

  The material parameters can be updated at any	time.  In particular,
  glMaterial can be called between a call to glBegin and the corresponding
  call to glEnd.  If only a single material parameter is to be changed per
  vertex, however, glColorMaterial is preferred	over glMaterial	(see
  glColorMaterial).

Errors

  GL_INVALID_ENUM is generated if either face or pname is not an accepted
  value.

  GL_INVALID_VALUE is generated	if a specular exponent outside the range
  [0,128] is specified.

Associated Gets

  glGetMaterial

See Also

  glColorMaterial, glLight, glLightModel

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Last Edited: Fri Dec 6 11:18:03 EST 1996 by AFV
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