# 3Di Geometry Section

Geometries form the core of the 3Di file. This section starts with the keyword GEOMETRIES. Each geometry starts with the keyword GEOM.

Click on any block to go the specific topic.

## Geometry Types

Four classes of 3D geometries are supported which have been developed for PCB and IC package layouts

• extrusion [EXTR] - a 2D boundary extruded along Z into 3D
• wire [WIRE] modeling bond wires.
• sphere [SPHERE] - modeling solder ball pads.
• barrel [BARL] - modeling a "squashed" ball pad or bump

## Geometry Properties/Attributes

Associating properties or attributes with each geometry is what gives the 3Di database intelligence. There are two types of attributes: direct and table.

Example of a GEOM and Attribute/Properties

```GEOM
ID 100001
OBJECT 4
LAYER 1
COLOR 1
NET 1
NET_PINS 1
```

### Direct vs. Table Attributes

Direct attributes are generally used only once or a few times. They take the form: ATTRIBUTE_NAME VALUE. An example of a direct attribute would be the ID (or handle) These ID's are used to correlate 3D geometries with the 2D geometries that generated them. (Cadence Allegro) Since they are, by definition, unique, there would be no reason to build a table of IDs and then refer to them by the table index.

On the other hand, a net label is likely to be used to multiple conductor geometries. In such a case a TABLE NET would be created and geometries would be labeled using the index to the appropriate net.

This is why it is required to create a list of tables at the beginning of the 3Di file. Only in that fashion can the 3Di parser determine whether an attribute is direct (i.e. the property name does not appear in the list of tables) or table based. The tables themselves can be placed at the end of the 3Di database.

### Recommended Minimum Attributes

While it is technically legal to write geometries with no attributes, we recommend that the 3Di writer includes these attributes at a minimum:

• OBJECT - if no OBJECT attribute is assigned the viewer may produce results that don't look correct.
• COLOR - if no COLOR attribute is assigned, the viewer will display everything as white. If the background is also white then then there will appear to be nothing at all on the screen.
• LAYER - If no LAYER attribute is assigned, then the viewer will not be able to selectively turn on/off entities so the user may have some problems investigating the structures.