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8. Adding a New Model

This chapter describes the basic steps for creating a new model. It describes how the source files should be laid out, how to register models with the server and how to work with GNU Autotools.

N.B. These instructions assume you are working from CVS, not a source snap-shot or distribution.
Developers should consult Chapter 7 for detailed information on model class implementation. Developers are also advised to read Appendix B for Gazebo coding standards and conventions.

8.1 Model Source Files

Source code for models is located under server/models/, with a separate directory for each model. Model directory names should match model class names, i.e., the SickLMS200 model is found the server/models/SickLMS200/ directory. Layout of files within the model directory is at the developers discretion; by convention, however, models are comprised of a single header file containing the model class declarations, and one or more source files containing the class definitions. Thus, the SickLMS200 model is comprised of SickLMS200.hh and

The recommended way to create a new model is to copy an existing model with similar functionality, and perform some judicious search-and-replacing. In addition to changing the class name (e.g. from SickLMS200 to MyModel), developers must also change the model's naked New function. E.g., NewSickLMS200() becomes NewMyModel(). This function is used to create instances of the model class at run-time.

8.2 Registering the Model

Models must be registered with the server. Registration is handled by the ModelFactory class, which can be found in server/ Registration is a two step process:

  1. Add a declaration for the new models creation function; e.g.:
    extern Model* NewMyModel( World *world );
    The INCLUDE macro will be defined automagically by Autotools (see below) if and only if the model should be included in the build.
  2. In the ModelFactory::NewModel() function, add a clause for the new model, e.g.:
      if (strcmp(classname, "MyModel") == 0)
        return NewMyModel(world);
    This line allows the server to look up the model by name and construct an appropriate class instance at run-time.

8.3 Working with GNU Autotools

Gazebo uses GNU Autotools to managing the build process; while Autotools can be daunting for newcomers, the rewards are well worth the effort. When using Autotools, there are two key notions to bear in mind:

These configuration files are used to generate the Makefile's that will ultimately control the build process (developers should never manipulate Makefile's directly).

The basic process for adding a new model to the Autotools setup is as follows.

  1. Create for the new model:
  2. Modify in the server/models directory.
  3. Modify in the top-level directory.
  4. Re-generate the Makefile's:
Running make will now build the new driver.

next up previous contents
Next: 9. libgazebo  Up: 2 Developer Guide Previous: 7. Gazebo Architecture   Contents