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Variable Export

To use variables from your C++ code in UnigineScript, you need to export them. After that, they will be available on the script side.

  • External variables are read-only.
  • If a value of a registered variable is changed in the C++ code, it instantly changes in the script as well (unlike in case of constants).

See also

An example can be found in <UnigineSDK>/source/samples/Api/Scripts/Variable/ directory.

Variable Export Example

Let's say, you declared a number of variables on C++ side. To export them, you will need to do the following:

  1. Create a pointer to an external variable via MakeExternVariable().
  2. Register the variable via Unigine::Interpreter::addExternVariable().
  3. All variables are exported into a global namespace. To limit the scope of variable, use library namespace.
Source code (C++)
#include <UnigineInterpreter.h>

using namespace Unigine;

int main(int argc,char **argv) {

	int i = 0;
	float f = 0.0f;
	vec3 v3 = vec3(1.0f,2.0f,3.0f);
	vec4 v4 = vec4(0.1f,0.2f,0.3f,0.4f);
	float m[16] = { 0.0f, 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f,\
					8.0f, 9.0f, 10.0f, 11.0f, 12.0f, 13.0f, 14.0f, 15.0f };
	mat4 mat = mat4(m);
	quat q = quat(0.0f,0.0f,1.0f,0.0f);

	// export a variable and specify a name to access it from Unigine scripts
	Interpreter::addExternVariable("integer",MakeExternVariable(&i));
	Interpreter::addExternVariable("float_point",MakeExternVariable(&f));
	Interpreter::addExternVariable("vector3",MakeExternVariable(&v3));
	Interpreter::addExternVariable("vector4",MakeExternVariable(&v4));
	Interpreter::addExternVariable("matrix4",MakeExternVariable(&mat));
	Interpreter::addExternVariable("quaternion",MakeExternVariable(&q));

	Engine *engine = Engine::init(UNIGINE_VERSION,argc,argv);

	// enter the main loop
	while(engine->isDone() == 0) {
		engine->update();
		engine->render();
		engine->swap();
		// if a variable value is changed after it was registered, in scripts the value will be changed as well		
		i = 42;
	}

	// engine shutdown
	Engine::shutdown();

}

Access from Scripts

After the registration, you can access variables from a script by their registered names:

Source code (UnigineScript)
// my_world.cpp
int init() {

	log.message("Integer is %d\nFloat is %f\n",integer,float_point);
	log.message("Vector3 x is %d\nVector3 y is %f\n",vector3.x,vector3.y);
	log.message("Vector4 w is %d\n",vector4.w);
	log.message("Matrix4 m10 is %d\nMatrix4 m11 is %f\n",matrix4.m10,matrix4.m11);
	
	return 1;
}

Output

The following results will be printed into the console after launching the application:

Output
Integer is 0
Float is 0.000000
Vector3 x is 1
Vector3 y is 2.000000
Vector4 w is 0
Matrix4 m10 is 1
Matrix4 m11 is 5.000000

If you reload the world, the integer value that has been changed on the C++ side will appear in the console:

Output
Integer is 42
Float is 0.000000
Vector3 x is 1
Vector3 y is 2.000000
Vector4 w is 0
Matrix4 m10 is 1
Matrix4 m11 is 5.000000
Last update: 04.06.2018