Represents the "3DB" entry of the 3d annotation object.

It is an optional entry defined as part of the PDF 1.0 specification.

It contains a RectangleElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 298, page 513.

Adobe Supplement to the ISO 32000, BaseVersion: 1.7, ExtensionLevel: 3; Table: 9.33, page 55.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 309, page 640.

The 3DB entry holds the default background colour for the 3D viewport as an array of colour component values. This colour appears behind the model when the background style uses a solid colour.