OGRE, using camera

This post is the second post in my miniseries to OGRE graphics library and today we learn how to work with camera. Full source code listing for today camera sample can be found in ogre-guide repository.

previous posts in OGRE miniseries: OGRE starter guide

Content

Implementation
Building

Implementation

OGRE implements camera controler as CameraMan in OgreBites namespace.

Let’s start with our starter sample from previous post, we first define go() member function and CameraMan instance member variable. CameraMan requires handling keyboard, mouse input and frameRendered event from InputListener. Our ogre_app implementation can looks like this

class ogre_app
	: public ApplicationContext, public InputListener
{
public:
	void go();

private:
	void setup() override;

	// user input
	bool keyPressed(KeyboardEvent const & evt) override;
	bool keyReleased(KeyboardEvent const & evt) override;
	bool mouseMoved(MouseMotionEvent const & evt) override;
	bool mousePressed(MouseButtonEvent const & evt) override;
	bool mouseReleased(MouseButtonEvent const & evt) override;
	void frameRendered(Ogre::FrameEvent const & evt) override;

	unique_ptr<CameraMan> _cameraman;
};

With go() member function main() becomes

int main(int argc, char * argv[]) {
	ogre_app app;
	app.go();
	cout << "done\n";
	return 0;
}

and go() member function implementation looks

void ogre_app::go() {
	initApp();

	if (getRoot()->getRenderSystem())
		getRoot()->startRendering();

	closeApp();
}

User input handling functions (from InputListener) just forward event object to the corresponding CameraMan member function this way

bool ogre_app::keyPressed(KeyboardEvent const & evt) {
	return _cameraman->keyPressed(evt);
}

note: check out main.cpp to see keyReleased(), mouseMoved(), mousePressed() and mouseReleased() implementations

frameRendered() is implemented the same way, just forward FrameEvent object to corresponding member function

void ogre_app::frameRendered(FrameEvent const & evt) {
	_cameraman->frameRendered(evt);
}

In ogre_app::setup() member function we create floor graphics object with

MeshManager::getSingleton().createPlane("floor", ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME,
	Plane(Vector3::UNIT_Y, -1), 250, 250, 25, 25, true, 1, 15, 15, Vector3::UNIT_Z);

Entity * floor = scene->createEntity("Floor", "floor");
floor->setMaterialName("Examples/Rockwall");
floor->setCastShadows(false);
root_nd->attachObject(floor);

and OGRE head graphics object with

Vector3 const head_pos = {0, 30, 0};
SceneNode * head_nd = root_nd->createChildSceneNode();
head_nd->setPosition(head_pos);
Entity * head = scene->createEntity("ogrehead.mesh");
head_nd->attachObject(head);

then set camera to look at OGRE head this way

SceneNode * cam_nd = root_nd->createChildSceneNode();
cam_nd->setPosition(0, 30, 140);
cam_nd->lookAt(head_pos/2 + Vector3{0, 0, -1}, Node::TS_PARENT);

Initialize _cameraman member variable and set camera to free look mode with

_cameraman = make_unique<CameraMan>(cam_nd);
_cameraman->setStyle(CS_FREELOOK);

and at the end of setup() grab mouse with

setWindowGrab();

function calll.

Building

Building the project is easy, just download sample repository with

git clone https://github.com/sansajn/ogre-guide.git

command, go to camera/ directory and build camera sample with

cd strarter-guide/camera
scons

commands. On successfull build main binary should be created so run ./main command to run the sample. You should be now able to move with mouse and see that camera view is changing this way

We are done!