IRIX Base Documentation 2001 May/SGI IRIX Base Documentation 2001 May.iso/usr/share/catman/g_man/cat3/OpenGL/glfragmentlight.z/glfragmentlight

Text File | 2001-04-17 | 22.1 KB | 331 lines

ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))            OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee            ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))



NNNNAAAAMMMMEEEE
     ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttffffSSSSGGGGIIIIXXXX,,,, ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttiiiiSSSSGGGGIIIIXXXX,,,, ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttffffvvvvSSSSGGGGIIIIXXXX,,,,
     ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttiiiivvvvSSSSGGGGIIIIXXXX - set fragment light source parameters


CCCC SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNNN
     void ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttffffSSSSGGGGIIIIXXXX( GLenum _l_i_g_h_t,
                                GLenum _p_n_a_m_e,
                                GLfloat _p_a_r_a_m )
     void ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttiiiiSSSSGGGGIIIIXXXX( GLenum _l_i_g_h_t,
                                GLenum _p_n_a_m_e,
                                GLint _p_a_r_a_m )


PPPPAAAARRRRAAAAMMMMEEEETTTTEEEERRRRSSSS
     _l_i_g_h_t   Specifies a fragment light.  The number of fragment lights
             depends on the implementation.  They are identified by names of
             the form GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTi____SSSSGGGGIIIIXXXX where 0 _< i <
             GGGGLLLL____MMMMAAAAXXXX____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTSSSS____SSSSGGGGIIIIXXXX.

     _p_n_a_m_e   Specifies a single-valued fragment light source parameter for
             _l_i_g_h_t.  GGGGLLLL____SSSSPPPPOOOOTTTT____EEEEXXXXPPPPOOOONNNNEEEENNNNTTTT, GGGGLLLL____SSSSPPPPOOOOTTTT____CCCCUUUUTTTTOOOOFFFFFFFF,
             GGGGLLLL____CCCCOOOONNNNSSSSTTTTAAAANNNNTTTT____AAAATTTTTTTTEEEENNNNUUUUAAAATTTTIIIIOOOONNNN, GGGGLLLL____LLLLIIIINNNNEEEEAAAARRRR____AAAATTTTTTTTEEEENNNNUUUUAAAATTTTIIIIOOOONNNN, and
             GGGGLLLL____QQQQUUUUAAAADDDDRRRRAAAATTTTIIIICCCC____AAAATTTTTTTTEEEENNNNUUUUAAAATTTTIIIIOOOONNNN are accepted.

     _p_a_r_a_m   Specifies the value that parameter _p_n_a_m_e of fragment light source
             _l_i_g_h_t will be set to.

CCCC SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNNN
     void ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttffffvvvvSSSSGGGGIIIIXXXX( GLenum _l_i_g_h_t,
                                 GLenum _p_n_a_m_e,
                                 const GLfloat *_p_a_r_a_m_s )
     void ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttiiiivvvvSSSSGGGGIIIIXXXX( GLenum _l_i_g_h_t,
                                 GLenum _p_n_a_m_e,
                                 const GLint *_p_a_r_a_m_s )


PPPPAAAARRRRAAAAMMMMEEEETTTTEEEERRRRSSSS
     _l_i_g_h_t
          Specifies a fragment light.  The number of fragment lights depends
          on the implementation.  They are identified by names of the form
          GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTi____SSSSGGGGIIIIXXXX where 0 _< i < GGGGLLLL____MMMMAAAAXXXX____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTSSSS____SSSSGGGGIIIIXXXX.

     _p_n_a_m_e
          Specifies a fragment light source parameter for _l_i_g_h_t.  GGGGLLLL____AAAAMMMMBBBBIIIIEEEENNNNTTTT,
          GGGGLLLL____DDDDIIIIFFFFFFFFUUUUSSSSEEEE, GGGGLLLL____SSSSPPPPEEEECCCCUUUULLLLAAAARRRR, GGGGLLLL____PPPPOOOOSSSSIIIITTTTIIIIOOOONNNN, GGGGLLLL____SSSSPPPPOOOOTTTT____CCCCUUUUTTTTOOOOFFFFFFFF,
          GGGGLLLL____SSSSPPPPOOOOTTTT____DDDDIIIIRRRREEEECCCCTTTTIIIIOOOONNNN, GGGGLLLL____SSSSPPPPOOOOTTTT____EEEEXXXXPPPPOOOONNNNEEEENNNNTTTT, GGGGLLLL____CCCCOOOONNNNSSSSTTTTAAAANNNNTTTT____AAAATTTTTTTTEEEENNNNUUUUAAAATTTTIIIIOOOONNNN,
          GGGGLLLL____LLLLIIIINNNNEEEEAAAARRRR____AAAATTTTTTTTEEEENNNNUUUUAAAATTTTIIIIOOOONNNN, and GGGGLLLL____QQQQUUUUAAAADDDDRRRRAAAATTTTIIIICCCC____AAAATTTTTTTTEEEENNNNUUUUAAAATTTTIIIIOOOONNNN are accepted.

     _p_a_r_a_m_s
          Specifies a pointer to the value or values that parameter _p_n_a_m_e of
          fragment light source _l_i_g_h_t will be set to.



                                                                        PPPPaaaaggggeeee 1111






ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))            OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee            ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))



DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
     ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt sets the values of individual fragment light source
     parameters.  _l_i_g_h_t names the fragment light and is a symbolic name of the
     form GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTi____SSSSGGGGIIIIXXXX, where 0 _< i < GGGGLLLL____MMMMAAAAXXXX____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTSSSS____SSSSGGGGIIIIXXXX.
     _p_n_a_m_e specifies one of ten fragment light source parameters, again by
     symbolic name.  _p_a_r_a_m_s is either a single value or a pointer to an array
     that contains the new values.

     To enable and disable fragment lighting calculation, call ggggllllEEEEnnnnaaaabbbblllleeee and
     ggggllllDDDDiiiissssaaaabbbblllleeee with argument GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTIIIINNNNGGGG____SSSSGGGGIIIIXXXX. 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 ggggllllEEEEnnnnaaaabbbblllleeee and ggggllllDDDDiiiissssaaaabbbblllleeee with argument
     GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTi____SSSSGGGGIIIIXXXX.

     The ten fragment light parameters are as follows:

     GGGGLLLL____AAAAMMMMBBBBIIIIEEEENNNNTTTT          _p_a_r_a_m_s 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).

     GGGGLLLL____DDDDIIIIFFFFFFFFUUUUSSSSEEEE          _p_a_r_a_m_s 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
                         GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT0000____SSSSGGGGIIIIXXXX is (1, 1, 1, 1); for other
                         fragment lights, the initial value is (0, 0, 0, 0).

     GGGGLLLL____SSSSPPPPEEEECCCCUUUULLLLAAAARRRR         _p_a_r_a_m_s 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
                         GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT0000____SSSSGGGGIIIIXXXX is (1, 1, 1, 1); for other
                         fragment lights, the initial value is (0, 0, 0, 0).

     GGGGLLLL____PPPPOOOOSSSSIIIITTTTIIIIOOOONNNN         _p_a_r_a_m_s contains four integer or floating-point values
                         that specify the position of the fragment light in
                         homogeneous object coordinates.  Both integer and



                                                                        PPPPaaaaggggeeee 2222






ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))            OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee            ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))



                         floating-point values are mapped directly.  Neither
                         integer nor floating-point values are clamped.

                         The position is transformed by the modelview matrix
                         when ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt 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.

     GGGGLLLL____SSSSPPPPOOOOTTTT____DDDDIIIIRRRREEEECCCCTTTTIIIIOOOONNNN   _p_a_r_a_m_s 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 ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt is called
                         (just as if it were a normal), and it is stored in
                         eye coordinates.  It is significant only when
                         GGGGLLLL____SSSSPPPPOOOOTTTT____CCCCUUUUTTTTOOOOFFFFFFFF is not 180, which it is initially.
                         The initial direction is (0, 0, -1).

     GGGGLLLL____SSSSPPPPOOOOTTTT____EEEEXXXXPPPPOOOONNNNEEEENNNNTTTT    _p_a_r_a_m_s 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
                         GGGGLLLL____SSSSPPPPOOOOTTTT____CCCCUUUUTTTTOOOOFFFFFFFF, next paragraph).  The initial spot
                         exponent is 0, resulting in uniform fragment light
                         distribution.

     GGGGLLLL____SSSSPPPPOOOOTTTT____CCCCUUUUTTTTOOOOFFFFFFFF      _p_a_r_a_m_s 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



                                                                        PPPPaaaaggggeeee 3333






ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))            OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee            ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))



                         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.

     GGGGLLLL____CCCCOOOONNNNSSSSTTTTAAAANNNNTTTT____AAAATTTTTTTTEEEENNNNUUUUAAAATTTTIIIIOOOONNNN

     GGGGLLLL____LLLLIIIINNNNEEEEAAAARRRR____AAAATTTTTTTTEEEENNNNUUUUAAAATTTTIIIIOOOONNNN

     GGGGLLLL____QQQQUUUUAAAADDDDRRRRAAAATTTTIIIICCCC____AAAATTTTTTTTEEEENNNNUUUUAAAATTTTIIIIOOOONNNN
                         _p_a_r_a_m_s 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.

NNNNOOOOTTTTEEEESSSS
     It is always the case that GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTi____SSSSGGGGIIIIXXXX =
     GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT0000____SSSSGGGGIIIIXXXX + i.

EEEERRRRRRRROOOORRRRSSSS
     GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____EEEENNNNUUUUMMMM is generated if either _l_i_g_h_t or _p_n_a_m_e is not an accepted
     value.

     GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____VVVVAAAALLLLUUUUEEEE 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.

     GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____OOOOPPPPEEEERRRRAAAATTTTIIIIOOOONNNN is generated if ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt is executed between
     the execution of ggggllllBBBBeeeeggggiiiinnnn and the corresponding execution of ggggllllEEEEnnnndddd.

AAAASSSSSSSSOOOOCCCCIIIIAAAATTTTEEEEDDDD GGGGEEEETTTTSSSS
     ggggllllGGGGeeeettttFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt
     ggggllllIIIIssssEEEEnnnnaaaabbbblllleeeedddd with argument GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTIIIINNNNGGGG____SSSSGGGGIIIIXXXX








                                                                        PPPPaaaaggggeeee 4444






ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))            OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee            ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt((((3333GGGG))))



MACHINE DEPENDENCIES
     The SSSSGGGGIIIIXXXX____ffffrrrraaaaggggmmmmeeeennnntttt____lllliiiigggghhhhttttiiiinnnngggg extension is supported only on OOOOccccttttaaaannnneeee2222 VVVVPPPPrrrroooo
     systems.

     On OOOOccccttttaaaannnneeee2222 VVVVPPPPrrrroooo 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 the texture matrix is set up to
     be projective.  (A projective texture matrix is defined to be one in
     which any of the 13th, 14th or 15th elements is non-zero.)  In addition,
     if either two-sided lighting or fragment lighting is in effect,
     projective texture effects will always be processed on a per-vertex
     basis.


SSSSEEEEEEEE AAAALLLLSSSSOOOO
     ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttCCCCoooolllloooorrrrMMMMaaaatttteeeerrrriiiiaaaallll, ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellll, ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttMMMMaaaatttteeeerrrriiiiaaaallll







































                                                                        PPPPaaaaggggeeee 5555