# Extending HOOPS Exchange

By default, HOOPS Exchange does not load all functions exposed by the API. Some functions must be explicitly requested in order to access them.

HOOPS Exchange identifies two types of such functions: experimental and extensions. Both are enabled by defining a C macro, either at the compiler level or within the code.

## Experimental Functions

Experimental functions are available when `A3DAPI_EXPERIMENTAL` is defined. This macro includes the A3DSDKExperimental.h header file, which is provided along with the standard headers.

When `A3DAPI_EXPERIMENTAL` is defined, your compiler will output a message to highlight the use of experimental features.

Since HOOPS Exchange 2024.7.0, we introduce a first experimental feature with T-Junctions Detection and Removal.

## Extension Functions

Extension functions are provided for specific use cases that fall outside the usual HOOPS Exchange API scope. To enable them, define `A3DAPI_EXTENSIONS`.

As of HOOPS Exchange 2026.3.0, no extension functions are available.

## Deprecated Functions

Since HOOPS Exchange 2025.1.0, the function deprecation process is:

1. In any release, the function is marked as deprecated in the documentation and header files, with a removal date.
2. In any later release, the function becomes opt-in: its name is prefixed with “deprecated_” and it is moved to the A3DSDKDeprecated.h header file.
3. In the release specified at step 1, the function is removed from the API.

Deprecated functions in the opt-in stage are available only when the `A3DAPI_DEPRECATED` macro is defined. To use them, define the `A3DAPI_DEPRECATED` macro before every inclusion of the A3DSDKDeprecated.h header file, either directly or through the A3DSDKIncludes.h header. It must also be defined beside the `INITIALIZE_A3D_API` macro.

When `A3DAPI_DEPRECATED` is defined, your compiler will output messages to highlight the use of deprecated features.

## Examples

This code extends the example provided in Initializing HOOPS Exchange, enabling experimental features by defining `A3DAPI_EXPERIMENTAL` on line 2.

    #define INITIALIZE_A3D_API
    #define A3DAPI_EXPERIMENTAL
    #include <A3DSDKIncludes.h>
    #include <hoops_license.h>

    // Usual initialization code
    int main(int argc, char* argv[])
    {
      A3DBool loaded = A3DSDKLoadLibraryA(PATH_TO_A3DLIBS_DIR);
      assert(loaded);

      A3DStatus result = A3DLicPutUnifiedLicense(HOOPS_LICENSE);
      assert(result == A3D_SUCCESS);

      result = A3DDllInitialize(A3D_DLL_MAJORVERSION, A3D_DLL_MINORVERSION);
      assert(result == A3D_SUCCESS);

      // HOOPS Exchange is now ready to use!

      A3DDllTerminate();
      A3DSDKUnloadLibrary();

      return EXIT_SUCCESS;
    }

`A3DAPI_EXPERIMENTAL` and `A3DAPI_EXTENSIONS` must also be defined in any source file that calls one of these additional functions.

This code extends the example provided in Initializing HOOPS Exchange, enabling deprecated features by defining `A3DAPI_DEPRECATED` on line 2 and calling a deprecated function on line 19.

    // main.c file
    #define INITIALIZE_A3D_API
    #define A3DAPI_DEPRECATED
    #include <A3DSDKIncludes.h>
    #include <hoops_license.h>

    extern void CallDeprecatedFunction();

    // Usual initialization code
    int main(int argc, char* argv[])
    {
      A3DBool loaded = A3DSDKLoadLibraryA(PATH_TO_A3DLIBS_DIR);
      assert(loaded);

      A3DStatus result = A3DLicPutUnifiedLicense(HOOPS_LICENSE);
      assert(result == A3D_SUCCESS);

      result = A3DDllInitialize(A3D_DLL_MAJORVERSION, A3D_DLL_MINORVERSION);
      assert(result == A3D_SUCCESS);

      // HOOPS Exchange is now ready to use!
      CallDeprecatedFunction();

      A3DDllTerminate();
      A3DSDKUnloadLibrary();

      return EXIT_SUCCESS;
    }

    // other.c file
    #define A3DAPI_DEPRECATED
    #include <A3DSDKDeprecated.h>

    // Call a deprecated function
    void CallDeprecatedFunction()
    {
      // Let's call a deprecated function to check
      A3DStatus result = deprecated_A3DEnableHandleSIGSEGV();
      assert(result == A3D_SUCCESS);
    }

`A3DAPI_DEPRECATED` must also be defined in any source file that calls one of the deprecated functions.

For simplicity, you can define the macros at the compiler level using a compiler option such as `/D` or `-D`.

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