New User Guide

The list of topics below represents a “guided tour” of information found in this documentation that, when processed in order, can help the new user quickly develop an understanding of 3DEC in its design, capabilities, and use.


The first two topics here are found in the Itasca Software Guide, a major section of this documentation that contains all material shared commonly between the programs FLAC, 3DEC, and PFC. The major section on 3DEC is limited to material specific to the program. The 3DEC user will move back-and-forth between these two major headings when consulting the program documentation.

General Approach

3DEC is numerical modeling software. This topic will provide an overview of the practice, its potential and its limitations.

Solution Procedure

A generalized workflow for problem solution is illustrated here. While 3DEC is open-ended software that can be used in myriad ways, the majority of modeling projects will likely follow some or all of this flow.

Tutorial: Quick Start (3DEC)

In a hurry to get hands on? This tutorial exists for that exact purpose. Note, along the way, how even the quick tutorial follows the methodology illustrated in “Solution Procedure.”


By the time the tutorial is completed, the new user should have a solid initial grasp on how to work with 3DEC.

The next items here represent first stops for a variety of possible avenues of further self-guided exploration. They do not have the same order-dependence as the topics above.

3DEC Examples

A substantial library of example problems is provided on this page. Users who know what kind of problem they’d like to solve may wish to familiarize themselves with the offerings provided here. Note these examples are standalone projects. There are considerably more illustrative examples provided throughout the documentation. Becoming familiar with the 3DEC Examples Index is highly recommended. Searching for examples across all topic areas becomes increasingly important as proficiency increases, and this page should become the user’s primary access point for that purpose.

3DEC Commands Index and Index: 3DEC FISH Functions

By this point the user should have a comfortable familiarity with 3DEC as command-driven software. The thorough-minded user may consider a top-to-bottom perusal of the program’s commands and built-in FISH functions. These indexes are optimal starting points for doing so.

Index: Common Commands and Index: Common FISH

The preceding exercise is also recommended for the shared commands and FISH. Note that this familiarization will underline what is meant by “3DEC-specific” and “shared by all Itasca software,” a distinction that is pervasively used throughout this documentation (and see Note above).

FISH Scripting Reference

Using scripting to customize any aspect of the modeling process, either with FISH or with Python, both opens up a tremendous amount of power and ends the user’s status as a novice. From the simplest utility to full automation, parameterization, or specialized calculation (or all of the above)—the path to all model- and modeling-process customizations heads in this direction.