glFragmentLight(3G)
glFragmentLightfSGIX, glFragmentLightiSGIX, glFragmentLightfvSGIX, glFragmentLightivSGIX - set fragment light source parameters
As shipped in IRIX 6.5.19. Last changed in IRIX 6.5.19.
NAME glFragmentLightfSGIX, glFragmentLightiSGIX, glFragmentLightfvSGIX, glFragmentLightivSGIX - set fragment light source parameters C SPECIFICATION void glFragmentLightfSGIX( GLenum light, GLenum pname, GLfloat param ) void glFragmentLightiSGIX( GLenum light, GLenum pname, GLint param ) PARAMETERS light Specifies a fragment light. The number of fragment lights depends on the implementation. They are identified by names of the form GL_FRAGMENT_LIGHTi_SGIX where 0 < i < GL_MAX_FRAGMENT_LIGHTS_SGIX. pname Specifies a single-valued fragment light source parameter for light. GL_SPOT_EXPONENT, GL_SPOT_CUTOFF, GL_CONSTANT_ATTENUATION, GL_LINEAR_ATTENUATION, and GL_QUADRATIC_ATTENUATION are accepted. param Specifies the value that parameter pname of fragment light source light will be set to. C SPECIFICATION void glFragmentLightfvSGIX( GLenum light, GLenum pname, const GLfloat *params ) void glFragmentLightivSGIX( GLenum light, GLenum pname, const GLint *params ) PARAMETERS light Specifies a fragment light. The number of fragment lights depends on the implementation. They are identified by names of the form GL_FRAGMENT_LIGHTi_SGIX where 0 < i < GL_MAX_FRAGMENT_LIGHTS_SGIX. pname Specifies a fragment light source parameter for light. GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR, GL_POSITION, GL_SPOT_CUTOFF, GL_SPOT_DIRECTION, GL_SPOT_EXPONENT, GL_CONSTANT_ATTENUATION, GL_LINEAR_ATTENUATION, and GL_QUADRATIC_ATTENUATION are accepted. params Specifies a pointer to the value or values that parameter pname of fragment light source light will be set to. DESCRIPTION glFragmentLight sets the values of individual fragment light source parameters. light names the fragment light and is a symbolic name of the form GL_FRAGMENT_LIGHTi_SGIX, where 0 < i < GL_MAX_FRAGMENT_LIGHTS_SGIX. pname specifies one of ten fragment light source parameters, again by symbolic name. params is either a single value or a pointer to an array that contains the new values. To enable and disable fragment lighting calculation, call glEnable and glDisable with argument GL_FRAGMENT_LIGHTING_SGIX. Fragment lighting is initially disabled. When it is enabled, light sources that are enabled contribute to the fragment lighting calculation. Fragment light source i is enabled and disabled using glEnable and glDisable with argument GL_FRAGMENT_LIGHTi_SGIX. The ten fragment light parameters are as follows: GL_AMBIENT params contains four integer or floating-point values that specify the ambient RGBA intensity of the fragment light. 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 fragment light intensity is (0, 0, 0, 1). GL_DIFFUSE params contains four integer or floating-point values that specify the diffuse RGBA intensity of the fragment light. 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 value for GL_FRAGMENT_LIGHT0_SGIX is (1, 1, 1, 1); for other fragment lights, the initial value is (0, 0, 0, 0). GL_SPECULAR params contains four integer or floating-point values that specify the specular RGBA intensity of the fragment light. 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 value for GL_FRAGMENT_LIGHT0_SGIX is (1, 1, 1, 1); for other fragment lights, the initial value is (0, 0, 0, 0). GL_POSITION params contains four integer or floating-point values that specify the position of the fragment light in homogeneous object coordinates. Both integer and floating-point values are mapped directly. Neither integer nor floating-point values are clamped. The position is transformed by the modelview matrix when glFragmentLight is called (just as if it were a point), and it is stored in eye coordinates. If the w component of the position is 0, the fragment light is treated as a directional source. Diffuse and specular fragment lighting calculations take the light's direction, but not its actual position, into account, and attenuation is disabled. Otherwise, diffuse and specular fragment lighting calculations are based on the actual location of the fragment light in eye coordinates, and attenuation is enabled. The initial position is (0, 0, 1, 0); thus, the initial fragment light source is directional, parallel to, and in the direction of the -z axis. GL_SPOT_DIRECTION params contains three integer or floating-point values that specify the direction of the fragment light in homogeneous object coordinates. Both integer and floating-point values are mapped directly. Neither integer nor floating-point values are clamped. The spot direction is transformed by the inverse of the modelview matrix when glFragmentLight is called (just as if it were a normal), and it is stored in eye coordinates. It is significant only when GL_SPOT_CUTOFF is not 180, which it is initially. The initial direction is (0, 0, -1). GL_SPOT_EXPONENT params is a single integer or floating-point value that specifies the intensity distribution of the fragment light. Integer and floating-point values are mapped directly. Only values in the range [0,128] are accepted. Effective fragment light intensity is attenuated by the cosine of the angle between the direction of the fragment light and the direction from the fragment light to the vertex being lighted, raised to the power of the spot exponent. Thus, higher spot exponents result in a more focused fragment light source, regardless of the spot cutoff angle (see GL_SPOT_CUTOFF, next paragraph). The initial spot exponent is 0, resulting in uniform fragment light distribution. GL_SPOT_CUTOFF params is a single integer or floating-point value that specifies the maximum spread angle of a fragment light source. Integer and floating-point values are mapped directly. Only values in the range [0,90] and the special value 180 are accepted. If the angle between the direction of the fragment light and the direction from the light to the vertex being lighted is greater than the spot cutoff angle, the fragment light is completely masked. Otherwise, its intensity is controlled by the spot exponent and the attenuation factors. The initial spot cutoff is 180, resulting in uniform fragment light distribution. GL_CONSTANT_ATTENUATION GL_LINEAR_ATTENUATION GL_QUADRATIC_ATTENUATION params is a single integer or floating-point value that specifies one of the three fragment light attenuation factors. Integer and floating-point values are mapped directly. Only nonnegative values are accepted. If the fragment light is positional, rather than directional, its intensity is attenuated by the reciprocal of the sum of the constant factor, the linear factor times the distance between the fragment light and the vertex being lighted, and the quadratic factor times the square of the same distance. The initial attenuation factors are (1, 0, 0), resulting in no attenuation. NOTES It is always the case that GL_FRAGMENT_LIGHTi_SGIX = GL_FRAGMENT_LIGHT0_SGIX + i. ERRORS GL_INVALID_ENUM is generated if either light or pname is not an accepted value. GL_INVALID_VALUE is generated if a spot exponent value is specified outside the range [0,128], or if spot cutoff is specified outside the range [0,90] (except for the special value 180), or if a negative attenuation factor is specified. GL_INVALID_OPERATION is generated if glFragmentLight is executed between the execution of glBegin and the corresponding execution of glEnd. ASSOCIATED GETS glGetFragmentLight glIsEnabled with argument GL_FRAGMENT_LIGHTING_SGIX MACHINE DEPENDENCIES The SGIX_fragment_lighting extension is supported only on Octane2 VPro systems. On Octane2 VPro systems, use of the texture q coordinate to achieve projective texture effects will be processed on a per-vertex basis instead of a per-pixel basis, unless the texture matrix is set up to be projective. (A projective texture matrix, specified as 16-element array M, is defined to be one in which any of the M[3], M[7], or M[11] array elements is non-zero.) In addition, if either two-sided lighting or fragment lighting or separate specular lighting is in effect, projective texture effects will always be processed on a per-vertex basis. SEE ALSO glFragmentColorMaterial, glFragmentLightModel, glFragmentMaterial