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                                                829
       SECTION 9.5                                                                  3D Artwork



       For example, these controls enable underlying nodes to be revealed, by making
       the overlying nodes transparent or by moving them out of the way.

       Note: Do not confuse nodes with view nodes. A node is a PDF dictionary that spec-
       ifies an area in 3D artwork, while a view node is a parameter in the 3D artwork
       that specifies a view.

       Table 9.47 shows the entries in a 3D node dictionary.

                           TABLE 9.47 Entries in a 3D node dictionary
KEY                     TYPE          VALUE

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

N                       text string   (Required) The name of the node being described by the node dic-
                                      tionary. If the Subtype of the corresponding 3D Stream is U3D, this
                                      entry corresponds to the field Node block name, as described in
                                      the Universal 3D file format specification (see Bibliography). In the
                                      future, nodes may be described using other 3D conventions.
                                      Note: When comparing this entry to node names for a particular con-
                                      vention (such as Universal 3D), PDF viewer applications must trans-
                                      late between the PDF text encoding used by PDF and the character
                                      encoding specified in the 3D stream.

O                       number        (Optional) A number in the range [0, 1] indicating the opacity of
                                      the geometry supplied by this node using a standard additive blend
                                      mode.
                                      If this entry is absent, the viewer should use the opacity specified
                                      for the parent node or for the 3D artwork (in ascending order).

V                       boolean       (Optional) A flag indicating the visibility of this node. If true, then
                                      the node is visible. If false, then the node is not visible.
                                      If this entry is absent, the viewer should use the visibility specified
                                      for the parent node or for the 3D artwork (in ascending order).

M                       array         (Optional) A 12-element 3D transformation matrix that specifies
                                      the position and orientation of this node, relative to its parent, in
                                      world coordinates (see Section 9.5.4, “Coordinate Systems for 3D).

       The N entry specifies which node in the 3D stream corresponds to this node dic-
       tionary.

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