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

Text File | 2001-04-17 | 16.4 KB | 199 lines

ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellll((((3333GGGG))))       OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee       ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellll((((3333GGGG))))



NNNNAAAAMMMMEEEE
     ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellllffffSSSSGGGGIIIIXXXX,,,, ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeelllliiiiSSSSGGGGIIIIXXXX,,,,
     ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellllffffvvvvSSSSGGGGIIIIXXXX,,,, ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeelllliiiivvvvSSSSGGGGIIIIXXXX - set the lighting
     model parameters


CCCC SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNNN
     void ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellllffffSSSSGGGGIIIIXXXX( GLenum _p_n_a_m_e,
                                     GLfloat _p_a_r_a_m )
     void ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeelllliiiiSSSSGGGGIIIIXXXX( GLenum _p_n_a_m_e,
                                     GLint _p_a_r_a_m )


PPPPAAAARRRRAAAAMMMMEEEETTTTEEEERRRRSSSS
     _p_n_a_m_e   Specifies a single-valued lighting model parameter.
             GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____LLLLOOOOCCCCAAAALLLL____VVVVIIIIEEEEWWWWEEEERRRR____SSSSGGGGIIIIXXXX,
             GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____NNNNOOOORRRRMMMMAAAALLLL____IIIINNNNTTTTEEEERRRRPPPPOOOOLLLLAAAATTTTIIIIOOOONNNN____SSSSGGGGIIIIXXXX, and
             GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____TTTTWWWWOOOO____SSSSIIIIDDDDEEEE____SSSSGGGGIIIIXXXX are accepted.

     _p_a_r_a_m   Specifies the value that _p_a_r_a_m will be set to.

CCCC SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNNN
     void ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellllffffvvvvSSSSGGGGIIIIXXXX( GLenum _p_n_a_m_e,
                                      const GLfloat *_p_a_r_a_m_s )
     void ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeelllliiiivvvvSSSSGGGGIIIIXXXX( GLenum _p_n_a_m_e,
                                      const GLint *_p_a_r_a_m_s )


PPPPAAAARRRRAAAAMMMMEEEETTTTEEEERRRRSSSS
     _p_n_a_m_e
          Specifies a lighting model parameter.
          GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____AAAAMMMMBBBBIIIIEEEENNNNTTTT____SSSSGGGGIIIIXXXX,
          GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____LLLLOOOOCCCCAAAALLLL____VVVVIIIIEEEEWWWWEEEERRRR____SSSSGGGGIIIIXXXX,
          GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____NNNNOOOORRRRMMMMAAAALLLL____IIIINNNNTTTTEEEERRRRPPPPOOOOLLLLAAAATTTTIIIIOOOONNNN____SSSSGGGGIIIIXXXX, and
          GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____TTTTWWWWOOOO____SSSSIIIIDDDDEEEE____SSSSGGGGIIIIXXXX are accepted.

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

DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
     ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellll sets the lighting model parameter.  _p_n_a_m_e names a
     parameter and _p_a_r_a_m_s gives the new value.  There are three lighting model
     parameters:

     GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____AAAAMMMMBBBBIIIIEEEENNNNTTTT____SSSSGGGGIIIIXXXX
               _p_a_r_a_m_s 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



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ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellll((((3333GGGG))))       OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee       ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellll((((3333GGGG))))



               clamped.  The initial ambient scene intensity is (0.2, 0.2,
               0.2, 1.0).

     GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____LLLLOOOOCCCCAAAALLLL____VVVVIIIIEEEEWWWWEEEERRRR____SSSSGGGGIIIIXXXX
               _p_a_r_a_m_s is a single integer or floating-point value that
               specifies how specular reflection angles are computed.  If
               _p_a_r_a_m_s 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 fragment in eye
               coordinates.  Otherwise, specular reflections are computed from
               the origin of the eye coordinate system.  The initial value is
               0.

     GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____NNNNOOOORRRRMMMMAAAALLLL____IIIINNNNTTTTEEEERRRRPPPPOOOOLLLLAAAATTTTIIIIOOOONNNN____SSSSGGGGIIIIXXXX
               _p_a_r_a_m_s must be either GGGGLLLL____FFFFLLLLAAAATTTT or GGGGLLLL____SSSSMMMMOOOOOOOOTTTTHHHH, and controls how
               normals are selected for use in the fragment lighting
               computations.  If GGGGLLLL____FFFFLLLLAAAATTTT is selected for the lighting model,
               the normal from the provoking vertex of the primitive is used
               for all fragment lighting computations.  If GGGGLLLL____SSSSMMMMOOOOOOOOTTTTHHHH is
               specified a normal is computed for each fragment using the
               normals from all of the vertices of the primitive.

     GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____TTTTWWWWOOOO____SSSSIIIIDDDDEEEE____SSSSGGGGIIIIXXXX
               _p_a_r_a_m_s 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 _p_a_r_a_m_s is 0 (or
               0.0), one-sided lighting is specified, and only the _f_r_o_n_t
               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 _b_a_c_k
               material parameters, and have their normals reversed before the
               lighting equation is evaluated.  Vertices of front-facing
               polygons are always lighted using the _f_r_o_n_t material
               parameters, with no change to their normals. The initial value
               is 0.

     In RGBA mode, the lighted color of a fragment 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 fragment's normal with the
     normalized vector from the fragment 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 fragment-to-eye and fragment-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



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ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellll((((3333GGGG))))       OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee       ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhttttMMMMooooddddeeeellll((((3333GGGG))))



     fragment 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 fragment ranges
     from the ambient to the specular values passed to ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttMMMMaaaatttteeeerrrriiiiaaaallll
     using GGGGLLLL____CCCCOOOOLLLLOOOORRRR____IIIINNNNDDDDEEEEXXXXEEEESSSS.  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.

EEEERRRRRRRROOOORRRRSSSS
     GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____EEEENNNNUUUUMMMM is generated if _p_n_a_m_e is not an accepted value.

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

AAAASSSSSSSSOOOOCCCCIIIIAAAATTTTEEEEDDDD GGGGEEEETTTTSSSS
     ggggllllGGGGeeeetttt with argument GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____AAAAMMMMBBBBIIIIEEEENNNNTTTT____SSSSGGGGIIIIXXXX
     ggggllllGGGGeeeetttt with argument GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____LLLLOOOOCCCCAAAALLLL____VVVVIIIIEEEEWWWWEEEERRRR____SSSSGGGGIIIIXXXX
     ggggllllGGGGeeeetttt with argument GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____NNNNOOOORRRRMMMMAAAALLLL____IIIINNNNTTTTEEEERRRRPPPPOOOOLLLLAAAATTTTIIIIOOOONNNN____SSSSGGGGIIIIXXXX
     ggggllllGGGGeeeetttt with argument GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTT____MMMMOOOODDDDEEEELLLL____TTTTWWWWOOOO____SSSSIIIIDDDDEEEE____SSSSGGGGIIIIXXXX
     ggggllllIIIIssssEEEEnnnnaaaabbbblllleeeedddd with argument GGGGLLLL____FFFFRRRRAAAAGGGGMMMMEEEENNNNTTTT____LLLLIIIIGGGGHHHHTTTTIIIINNNNGGGG____SSSSGGGGIIIIXXXX


MMMMAAAACCCCHHHHIIIINNNNEEEE DDDDEEEEPPPPEEEENNNNDDDDEEEENNNNCCCCIIIIEEEESSSS
     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
     ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttLLLLiiiigggghhhhtttt, ggggllllFFFFrrrraaaaggggmmmmeeeennnnttttMMMMaaaatttteeeerrrriiiiaaaallll










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