CHAPTER 9
830
Multimedia Features
The
O
entry describes the opacity to be used when rendering this node, and the
V
entry determines whether or not the node is rendered at all. While a node with an
opacity of 0 is rendered in the same way as a non-visible node, having a separate
value for the visibility of a node allows interactive viewer applications to show/
hide partially transparent nodes, without overwriting the intended opacity of
those nodes.
The
M
entry specifies the node’s matrix relative to its parent, in world coordi-
nates. If an hierarchy of nodes is intended to be repositioned while still maintain-
ing its internal structure, then only the node at the root of the hierarchy needs to
be adjusted.
Example 9.4
3 0 obj
% Default node params with all shapes visible and opaque
[ << /Type /3DNode
/N (Sphere)
/O 1
/V true
/M [...]>>
<< /Type /3DNode
/N (Cone)
/O 1
/V true >>
<< /Type /3DNode
/N (Cube)
/O 1
/V true >>
]
4 0 obj
% Params with the cone hidden and the sphere semi-transparent
[ << /Type /3DNode
/N (Sphere)
/O 0.5
/V true >>
<< /Type /3DNode
/N (Cone)
/O 1
/V false >>
<< /Type /3DNode
/N (Cube)