Function ClearBuffer

Rendering/LICOpenGL2/vtkLineIntegralConvolution2D.cxx:298–334

Description: Clear the given buffer

  // Description:
  // Clear the given buffer
  void ClearBuffer(vtkOpenGLFramebufferObject* fbo, vtkTextureObject* tex,
    const vtkPixelExtent& viewExt, const deque<vtkPixelExtent>& extents)
  {
    vtkOpenGLState* ostate = fbo->GetContext()->GetState();

    // attach
    fbo->AddColorAttachment(0U, tex);
    fbo->ActivateDrawBuffers(1);
    DEBUG3CheckFrameBufferStatusMacro(GL_DRAW_FRAMEBUFFER);

    // clear the parts of the screen which we will modify
    // initially mask all fragments
    ostate->vtkglClearColor(0.0, 1.0, 0.0, 0.0);
    ostate->vtkglEnable(GL_SCISSOR_TEST);
    size_t nBlocks = extents.size();
    for (size_t e = 0; e < nBlocks; ++e)
    {
      vtkPixelExtent ext = extents[e];
      // add halo for linear filtering
      // since at most linear filtering requires
      // 4 pixels , clearing an extra 4 here
      // ensures we never access uninitialized
      // memory.
      ext.Grow(4);
      ext &= viewExt;

      unsigned int extSize[2];
      ext.Size(extSize);

      ostate->vtkglScissor(ext[0], ext[2], extSize[0], extSize[1]);
      ostate->vtkglClear(GL_COLOR_BUFFER_BIT);
    }
    ostate->vtkglDisable(GL_SCISSOR_TEST);
    // detach
    fbo->RemoveColorAttachments(1);
    fbo->DeactivateDrawBuffers();
  }

  // Description:
  // Activates the input textures. These are read only.