5. File-to-File Translation
This tutorial will step you through the ImportExport sample code that ships with HOOPS Exchange. This sample implements the most basic possible workflow, which is reading an input file, and writing it to a new format.
To follow along, you must have HOOPS Exchange installed, and be able to run the sample code that ships with it.
You can find that sample projects for HOOPS Exchange in the samples folder. On macOS and Linux, you are provided a Makefile for building the code. The Windows package contains a Visual Studio solution file. Whichever your platform, be sure you’re able to build and run the ImoprtExport sample code.
Open ImportExport.cpp in your editor. Since the sample is a complete implementation, you’re note required to add anything new to the program. To facilitate learning, we’ll examine each of the functional area with a deep dive into what exactly the code is doing for you.
At the top of the file, you’ll notice two lines of code pertinent to including and initializing HOOPS Exchange:
The definition of
INITIALIZE_A3D_API prior to including the Exchange
header causes initialization code to be included. This should only
appear in a single compilation unit of an application. For this sample,
we only have one - ImportExport.cpp.
In the body of main, you’ll find some logic for handling command line arguments. If you execute the program without specifying an input and/or an output file, defaults are used instead. The default input file is samples/data/catiaV5/CV5AquoBottle/Aquo Bottle.CATProduct. The default output file is the same as the input file with .prc appended.
Following the command line processing, you’ll see the following line of code:
This constructs an object that is declared and implemented inline. It is responsible for loading and initializing HOOPS Exchange. It also unlocks the product using your license key found in hoops_license.h. Furthermore, its destructor is implemented to de-initialize and unload HOOPS Exchange. This class is implemented inline, so you can examine its implementation.
Next, this sample connects callbacks for custom memory allocation and
free. This isn’t required to use HOOPS Exchange but can be useful when
debugging memory related issues. After connecting the memory callbacks,
the code connects a callback for handling information, warning, and
error messages from the library. Again, this isn’t required to use HOOPS
Exchange, but it can provide useful information. The samples all print
the messages received by the callback to
The heart of the sample is the next three lines of code:
It declares an import object, and export object, then uses the Convert
A3DSDKHOOPSExchangeLoader to perform the conversion. Each
of these classes and methods are implemented in
A3DSDKInternalConvert.hxx, so you can examine them more closely.
A3DImport class serves as a container for the input filename,
and an options struct that controls the behavior of the reader.
Internally, it initializes the options to the most common set of values.
A3DExport class serves as a contained for the output
filename, and an options struct that controls the behavior of the
writer. The class is implemented to examine the file extension and sets
an enumeration indicating the desired format.
The final step of this tutorial is the call to
implementation of this method first reads the input file, then uses the
filetype determined by the
A3DExport class to invoke the proper
function to write the desired output file format.
The file-to-file workflow is a common starting point for evaluating the
capabilities of HOOPS Exchange. Using the
ImportExport sample that
ships with the product, you can easily convert files from one format to
By completing this tutorial, you now have the knowledge of how to use HOOPS Exchange in this basic use case. Furthermore, by examining the implementation of the helper classes involved, you’ll have gained some insight into the use of the API itself.