Facsimile Simulation/Emulation Library

Cell files are typically encoded as 8-bit ASCII text, with whitespace (spaces, horizontal tabs and/or newline sequences) delimiting each field. Consecutive whitespace characters are treated as a single delimiter. The only exception to this rule is when text string data is present (applicable to Text and Text List cell types only): these must be entered on a separate line and be terminated by a newline sequence.

The file is made up of cell definitions; a cell can be a set, a primitive, a block definition, a block reference, an embedded image or a referenced image. Sets are an important cell type that contain lists of other cells, including other sets. Each cell inherits its translation, rotation, scale and (optionally) color from its parent set. Through the use of sets, a cell hierarchy is achieved.

Each cell has the following general format:

Note that much of the data is only present if an associated cell flag bit, contained within the cell header, is set; refer to the corresponding section for additional information.

All distances, timings and velocities specified in the cell file are in arbitrary units; AutoMod will assume these to be its default model units when reading in the cell file. If a model that exports a cell file has Feet for its distance units and Minutes for its time units, and the cell file is then imported by a model whose distance and time units are Millimeters and Seconds respectively, then the image will be the wrong size and, more seriously, any embedded kinematic joint information will be invalid.

By convention, the first cell in a cell file is a special Set termed the Root Set. The name of this Set is based upon the name of the file, with underscores replacing periods. For example, the file Car.cell would have a root set named Car_cell. The root set contains a single cell member called the Main Set, which typically has the name of the cell file without the extension. Extending the previous example, the name of the Main Set would be Car. The Main Set then contains the remainder of the cells making up the 3D image.

Note that cell files use the right-hand-rule for specifying cell geometry. To visualize right-hand-rule geometry, imagine a map aligned so that the X-axis runs from West to East and the Y-axis from South to North with the Z-axis being a measurement of elevation. Other CAD and 3D systems that use the right-hand-rule include AutoCAD and 3D Studio. A common alternative is the left-hand-rule, in which the X-axis runs from West to East, the Z-axis from North to South and the Y-axis handling elevation. The left-hand-rule is the default for OpenGL, OpenInventor, Direct3D, VRML and Java3D amongst others. When converting between these formats, it is important to apply the correct transformation to geometry data.