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Here I'll create and show how to use a function to convert 3D points to 2D points, which is useful for debugging purposes, for showing names over character heads, to highlight some locations/objects, etc.

This is made for projects which are based on the [http://www.maratis3d.org/?p=563 GUIDemo].

==Header==
<pre>
	unsigned int screenWidth, screenHeight;
	float ratio;
	MOCamera * GUI_camera;
	MOCamera * Game_camera;
	MScene * GUI_scene;
	MScene * Game_scene;
</pre>

==onBeginScene==
<pre>
	MEngine * engine = MEngine::getInstance(); // get the engine instance
	MLevel * level = engine->getLevel(); // get the current level
	GUI_scene = level->getSceneByName("GUI");
	Game_scene = level->getSceneByName("MyScene");

	MSystemContext * system = engine->getSystemContext();
	system->getScreenSize(&screenWidth, &screenHeight);
	ratio = (float)screenWidth/(float)screenHeight;

	GUI_camera = GUI_scene->getCameraByName("Camera");
	Game_camera = Game_scene->getCameraByName("MyCamera");
</pre>

==Function to convert 3D points to 2D points==
<pre>
MVector3 MyGame::to2D(MVector3 pos)
{
	pos = Game_camera->getProjectedPoint(pos);
	if(pos.z<1)
	{	pos.x = pos.x / screenWidth - 0.5f;
		pos.y = pos.y = 1 - (pos.y / screenHeight) - 0.5f;
		pos.x = GUI_camera->getPosition().x + pos.x * GUI_camera->getFov() * ratio;
		pos.y = GUI_camera->getPosition().y + pos.y * GUI_camera->getFov();
		pos.z = -10;
	}
	else pos.z = -10000;	//out of GUI_camera
	return pos;
}
</pre>

==Use example==
<pre>
MVector3 pos(50,50,50);
pos = to2D(pos);
char string[30]; sprintf_s(string,30,"%f %f %f",pos.x,pos.y,pos.z);
MOText * text = GUI_scene->getTextByName("MyText");
text->setText(string);
pos.y -= text->getBoundingBox()->min.y/2; //move it to its vertical center
text->setPosition(pos);
</pre>

==External links==
[http://www.cplusplus.com/reference/cstdio/sprintf/ sprintf]

[http://www.cplusplus.com/reference/cstdio/printf/ printf (for the specifier characters)]