Application Tutorial

This tutorial will decompose the testApp example, found in the Delta3D/Examples folder.

It is meant as a very simple introduction to the dtABC::Application class. When you run testApp.exe, this is what you should see:

The first thing we need to do is include some header files. In this example, we'll include all the header files which are required for this example. We could have also included the main headers dt.h and dtABC.h, which correspond to namespaces and subsequently, the libraries we need. When you include these header files, the library files get automatically linked in. Since we're not using the main header files, we have to setup our project file to link in the additional libraries and their dependencies.

#include <dtCore/camera.h>
#include <dtCore/globals.h>
#include <dtCore/object.h>
#include <dtCore/transform.h>
#include <dtABC/application.h>

Now we can set up our search paths to find the data files we'll use in the application. In this case, we append a couple of strings together, separated by a semi-colon:

int main()
{

   std::string dataPath = dtCore::GetDeltaDataPathList();

Now we can create a new dtABC::Application. Notice we're storing it as a dtCore::RefPtr. This will allow it to be delete automatrically when the variable goes out of scope. We're also passing in the name of a config file which will allow us to change some aspects of this application.

   dtCore::RefPtr<dtABC::Application> app = new dtABC::Application( "config.xml" );

Then we create a couple of dtCore::Object and give them files to load. Don't forget to add it to the Scene, or else it won't get rendered. To do this, we can just use dtABC::Application::AddDrawable().

   dtCore::RefPtr<dtCore::Object> terrain = new dtCore::Object( "Terrain" );
   terrain->LoadFile( "models/terrain_simple.ive" );
   app->AddDrawable( terrain.get() );

   //load an object
   dtCore::RefPtr<dtCore::Object> brdm = new dtCore::Object( "BRDM" );
   brdm->LoadFile( "models/brdm.ive" );
   app->AddDrawable( brdm.get() );

On the second dtCore::Object, lets set its position using the dtCore::Transform class. In this case, the Transform just changes the heading by 90 degrees.

   osg::Vec3 brdmPosition( 0.0f, 0.0f, 3.5f );
   osg::Vec3 brdmRotation( 90.0f, 0.0f, 0.0f );
   dtCore::Transform trans;
   trans.SetTranslation( brdmPosition );
   trans.SetRotation( brdmRotation );
   brdm->SetTransform( trans );

Now we can set up the dtCore::Camera position by giving it a position and a place to look at.

   
   //adjust the Camera position
   dtCore::Transform camPos;
   osg::Vec3 camXYZ( 0.f, -30.f, 15.f );
   osg::Vec3 lookAtXYZ ( brdmPosition );
   osg::Vec3 upVec ( 0.f, 0.f, 1.f );
   camPos.SetLookAt( camXYZ, lookAtXYZ, upVec );
   app->GetCamera()->SetTransform( camPos );

And finally, tell the dtABC::Application to configure and to run. The dtABC::Application::Run() method is blocking, meaning it won't return control back until the the Application has exited. To quit the app, just hit the escape key.

   app->Config();
   app->Run();

   return 0;

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