Blocks and layers in 3DC file

• Blocks and layers in 3DC file
• Block table records
• Layers

Block table records

The block structure of the converted model is exactly the same, than in the original model. 3DC file format does not support nested blocks, so the result will not contain any deep block structures. There are three different block structures: inline, template and instantiation blocks.

• Inline block. Contains a set of geometry data (objects). An object in the inline block is inserted to the location that is defined by the objects itself in world coordinate system (WCS). When an inline block is created, its location is set to (0, 0, 0) without any transformations. Inline blocks are named after the following naming convention “Inlineblock_#”, where ‘#’ is the number of the block: the first inline block is “Inlineblock_0”, the second is “Inlineblock_1”, etc.
• Template block. Defines also a set of geometry data, but this data is in a local or entity coordinate system (LCS or ECS). Template block can be used several times, for example a valve can be defined in a template block so that the same definition is used every time, when the valve is inserted to the model.
• Instantiation block. Creates an instance of a template block. This means that previously defined template block in 3DC file is inserted to the specified location with an orientation. Like it was mentioned earlier, the same template block can be instantiated several times using this approach.

Layers

eXchanger_In utilizes AutoCAD layers also. This feature makes the conversion result more structured and easier to browse. It is possible to display objects in the certain layer or do set operations for the all the objects in the same layers.

The conversion creates AutoCAD layers based on the system ids, which are defined in the 3DC file. For example, a 3DC file might contain the following instantiation block definition:

C +2JO0K2diJIYt2piF6V3Ie0 9321.92 8674 53449 0 1 0 -1 0 0 obi 196eb712-c579-4a65-8106-f1c142dbc087;sid 125;;

This line creates an AutoCAD block with the name “+2JO0K2diJIYt2piF6V3Ie0”, inserts it to the location (9321.92, 8674, 53449) with orientation for the x-axis = (0, 1, 0) and for the y-axis = (-1, 0, 0). The template block “+2JO0K2diJIYt2piF6V3Ie0” is on the layer, which is named as “System_125”. All the objects or blocks which belong to the system 125 are inserted on the same layer. This way, the system takes care of that there are no two or more objects with the same object id.

Note: It is not possible to define an object id for the created AutoCAD objects, because AutoCAD assigns them automatically.