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                                                    812
          CHAPTER 9                                                          Multimedia Features



                                               The Daily News


                                             New Planet
                                             Discovered!




                            FIGURE 9.8 3D annotation positioned on the page


          3D Background Dictionaries

          A 3D background dictionary defines the background over which a 3D view is to
          be drawn; the entries in a background dictionary are shown in Table 9.41. Cur-
          rently, only a single opaque color is supported, where the color must be defined in
          the DeviceRGB color space. 3D artwork may include transparent objects; howev-
          er, there is no interaction between such objects and objects drawn below the an-
          notation. In effect, the 3D artwork and its background form a transparency group
          whose flattened results have an opacity of 1 (see Chapter 7, “Transparency”).

          Note: An annotation’s normal appearance should have the same behavior with re-
          spect to transparency when the appearance is intended to depict the 3D artwork.
          This recommendation does not necessarily apply when the appearance is used for
          another purpose, such as a compatibility warning message.

                           TABLE 9.41 Entries in a 3D background dictionary
KEY          TYPE         VALUE

Type         name         (Optional) The type of PDF object that this dictionary describes; if present, must be
                          3DBG for a 3D background dictionary.

Subtype      name         (Optional) The type of background. The only valid value is SC (solid color), which
                          indicates a single opaque color. Default value: SC.

CS           name or      (Optional) The color space of the background. The only valid value is the name De-
             array        viceRGB. Default value: DeviceRGB.
                          Note: PDF consumers must be prepared to encounter other values that may be sup-
                          ported in future versions of PDF.

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