C SPECIFICATION

       void GLAPIENTRY glTexSubImage2D( GLenum target,
                                        GLint leve )

PARAMETERS

       target  Specifies the target texture.  Must be GL_TEXTURE_2D.

       leve    Specifies  the  level-of-detail  number.   Level  0 is the base
               image level.  Level n is the nth mipmap reduction image.

       _param3 Specifies a texel offset in the x direction within the  texture
               array.

       _param4 Specifies  a texel offset in the y direction within the texture
               array.

       _param5 Specifies the width of the texture subimage.

       _param6 Specifies the height of the texture subimage.

       _param7 Specifies the format of the pixel data.  The following symbolic
               values are accepted: GL_COLOR_INDEX, GL_RED, GL_GREEN, GL_BLUE,
               GL_ALPHA, GL_RGB, GL_BGR, GL_RGBA, GL_BGRA,  GL_LUMINANCE,  and
               GL_LUMINANCE_ALPHA.

       _param8 Specifies  the data type of the pixel data.  The following sym-
               bolic   values   are   accepted:   GL_UNSIGNED_BYTE,   GL_BYTE,
               GL_BITMAP,    GL_UNSIGNED_SHORT,   GL_SHORT,   GL_UNSIGNED_INT,
               GL_INT,            GL_FLOAT,            GL_UNSIGNED_BYTE_3_3_2,
               GL_UNSIGNED_BYTE_2_3_3_REV,            GL_UNSIGNED_SHORT_5_6_5,
               GL_UNSIGNED_SHORT_5_6_5_REV,         GL_UNSIGNED_SHORT_4_4_4_4,
               GL_UNSIGNED_SHORT_4_4_4_4_REV,       GL_UNSIGNED_SHORT_5_5_5_1,
               GL_UNSIGNED_SHORT_1_5_5_5_REV,         GL_UNSIGNED_INT_8_8_8_8,
               GL_UNSIGNED_INT_8_8_8_8_REV,   GL_UNSIGNED_INT_10_10_10_2,  and
               GL_UNSIGNED_INT_2_10_10_10_REV.

       _param9 Specifies a pointer to the image data in memory.

DESCRIPTION

       Texturing maps a portion of a specified texture image onto each graphi-
       cal  primitive  for  which texturing is enabled.  To enable and disable
       two-dimensional texturing, call glEnable and  glDisable  with  argument
       GL_TEXTURE_2D.

       glTexSubImage2D  redefines  a  contiguous subregion of an existing two-
       dimensional texture image.  The texels referenced  by  _param9  replace
       the  portion  of  the existing texture array with x indices _param3 and
       _eqnparam3+_eqnparam5-1, inclusive, and y  indices  _param4  and  _eqn-
       param4+_eqnparam6-1, inclusive.  This region may not include any texels
       outside the range of the texture array as it was originally  specified.
       GL_UNSIGNED_SHORT_4_4_4_4_REV,               GL_UNSIGNED_SHORT_5_5_5_1,
       GL_UNSIGNED_SHORT_1_5_5_5_REV,                 GL_UNSIGNED_INT_8_8_8_8,
       GL_UNSIGNED_INT_8_8_8_8_REV,       GL_UNSIGNED_INT_10_10_10_2,      and
       GL_UNSIGNED_INT_2_10_10_10_REV are available only if the GL version  is
       1.2 or greater.

       When  the  GL_ARB_multitexture  extension is supported, glTexSubImage2D
       specifies a two-dimensional sub texture for the current  texture  unit,
       specified with glActiveTextureARB.

       When  the  GL_ARB_imaging  extension  is supported, the RGBA components
       specified in _param9 may be processed by  the  imaging  pipeline.   See
       glTexImage1D for specific details.

ERRORS

       GL_INVALID_ENUM is generated if target is not GL_TEXTURE_2D.

       GL_INVALID_OPERATION  is  generated  if  the texture array has not been
       defined by a previous glTexImage2D operation.

       GL_INVALID_VALUE is generated if leve is less than 0.

       GL_INVALID_VALUE may be generated if  leve  is  greater  than  log2max,
       where max is the returned value of GL_MAX_TEXTURE_SIZE.

       GL_INVALID_VALUE   is  generated  if  _eqnparam3<-b,  (_eqnparam3+_eqn-
       param5)>(w-b), _eqnparam4<-b, or (_eqnparam4+_eqnparam6)>(h-b), where w
       is  the GL_TEXTURE_WIDTH, h is the GL_TEXTURE_HEIGHT, and b is the bor-
       der width of the texture image being  modified.   Note  that  w  and  h
       include twice the border width.

       GL_INVALID_VALUE is generated if _param5 or _param6 is less than 0.

       GL_INVALID_ENUM  is generated if _param7 is not an accepted format con-
       stant.

       GL_INVALID_ENUM is generated if _param8 is not a type constant.

       GL_INVALID_ENUM is generated if _param8 is GL_BITMAP and _param7 is not
       GL_COLOR_INDEX.

       GL_INVALID_OPERATION   is  generated  if  glTexSubImage2D  is  executed
       between the execution of glBegin and  the  corresponding  execution  of
       glEnd.

       GL_INVALID_OPERATION    is    generated    if   _param8   is   one   of
       GL_UNSIGNED_BYTE_3_3_2,                     GL_UNSIGNED_BYTE_2_3_3_REV,
       GL_UNSIGNED_SHORT_5_6_5,  or GL_UNSIGNED_SHORT_5_6_5_REV and _param7 is
       not GL_RGB.

       GL_INVALID_OPERATION   is   generated   if   _param8    is    one    of
       GL_UNSIGNED_SHORT_4_4_4_4,               GL_UNSIGNED_SHORT_4_4_4_4_REV,
       glTexSubImage3D, glTexParameter




                                                           GLTEXSUBIMAGE2D(3G)