RE: [Plib-users] Overriding face culling

[Norman V. <nh...@ca...>]

Paolo Leoncini writes:
> 
> Can anybody explain why? and how to force disabling back face culling?


Maybe this code snippet will help


  /*
    Multipass rendering sometimes required:

    * Wire plus filled
    * Filled-front-faces with wire backfaces.
    * Selected polygons have white wire faces.
  */

  if ( rendermode & RENDER_TEXTURE )
  {
    glEnable ( GL_TEXTURE_2D ) ;
    ssgOverrideTexture ( FALSE ) ;
  }
  else
  {
    glDisable ( GL_TEXTURE_2D ) ;
    ssgOverrideTexture ( TRUE ) ;
  }

  /*
    If filled AND not wire AND not backfaces - then need wire
    as a first pass.
  */

  if ( (rendermode & RENDER_FILLED    )!=0 &&
       (rendermode & RENDER_WIRE      )==0 &&
       (rendermode & RENDER_BACKFACES )==0 )
  {
    /* First pass: Both faces, wireframe */

    glPolygonMode ( GL_FRONT_AND_BACK, GL_LINE ) ;
    glDisable ( GL_CULL_FACE ) ;
    ssgOverrideCullface ( TRUE ) ;
    ssgCullAndDraw ( getSceneRoot() ) ;

    /* Zap the Z buffer */

    glClear ( GL_DEPTH_BUFFER_BIT ) ;

    /* Second pass: Front faces only - filled */

    glPolygonMode ( GL_FRONT_AND_BACK, GL_FILL ) ;
    glEnable ( GL_CULL_FACE ) ;
    ssgOverrideCullface ( FALSE ) ;
    ssgCullAndDraw ( getSceneRoot() ) ;
  }
  else

  /*
    If filled AND wire - then need wire as a second
    pass.
  */

    if ( (rendermode & RENDER_FILLED)!=0 &&
       (rendermode & RENDER_WIRE  )!=0 )
    {
      setOffsetProjectionMatrix ( PUSH_BACK ) ;
      glPolygonMode ( GL_FRONT_AND_BACK, GL_FILL ) ;
      glDisable ( GL_CULL_FACE ) ;
      ssgOverrideCullface ( TRUE ) ;
      ssgCullAndDraw ( getSceneRoot() ) ;

      glPolygonMode ( GL_FRONT_AND_BACK, GL_LINE ) ;
      glEnable ( GL_CULL_FACE ) ;
      ssgOverrideCullface ( FALSE ) ;
      ssgCullAndDraw ( getSceneRoot() ) ;
    }
    else

    /* We only need one pass.  */

    {
      if ( rendermode & RENDER_WIRE )
        glPolygonMode ( GL_FRONT_AND_BACK, GL_LINE ) ;
      else 
        glPolygonMode ( GL_FRONT_AND_BACK, GL_FILL ) ;

      if ( rendermode & RENDER_BACKFACES )
      {
        glDisable ( GL_CULL_FACE ) ;
        ssgOverrideCullface ( TRUE ) ;
      }
      else
      {
        glEnable ( GL_CULL_FACE ) ;
        ssgOverrideCullface ( FALSE ) ;
      }

      ssgCullAndDraw ( getSceneRoot() ) ;
    }

  glFinish () ;


Ciao

Norman