Name

glMaterial — specify material parameters for the lighting model

C Specification

void glMaterialf(GLenum face,
 GLenum pname,
 GLfloat param);
 
void glMaterialx(GLenum face,
 GLenum pname,
 GLfixed param);
 

Parameters

face

Specifies which face or faces are being updated. Must be 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 glMaterialxv(GLenum face,
 GLenum pname,
 const GLfixed * params);
 

Parameters

face

Specifies which face or faces are being updated. Must be 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, or GL_AMBIENT_AND_DIFFUSE.

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, 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, must be GL_FRONT_AND_BACK and specifies that both 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 fixed-point or floating-point values that specify the ambient RGBA reflectance of the material. The values are not clamped. The initial ambient reflectance is (0.2, 0.2, 0.2, 1.0).

GL_DIFFUSE

params contains four fixed-point or floating-point values that specify the diffuse RGBA reflectance of the material. The values are not clamped. The initial diffuse reflectance is (0.8, 0.8, 0.8, 1.0).

GL_SPECULAR

params contains four fixed-point or floating-point values that specify the specular RGBA reflectance of the material. The values are not clamped. The initial specular reflectance is (0, 0, 0, 1).

GL_EMISSION

params contains four fixed-point or floating-point values that specify the RGBA emitted light intensity of the material. The values are not clamped. The initial emission intensity is (0, 0, 0, 1).

GL_SHININESS

params is a single fixed-point or floating-point value that specifies the RGBA specular exponent of the material. Only values in the range [0, 128] are accepted. The initial specular exponent 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.

Notes

To change the diffuse and ambient material per vertex, color material can be used. To enable and disable GL_COLOR_MATERIAL, call glEnable and glDisable with argument GL_COLOR_MATERIAL. Color material is initially disabled.

While the ambient, diffuse, specular and emission material parameters all have alpha components, only the diffuse alpha component is used in the lighting computation.

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

glEnable, glLight, glLightModel

Copyright

Copyright © 2003-2004 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.