Camera
From Ogre Wiki
Camera - A viewpoint from which the scene will be rendered.
OGRE renders scenes from a camera viewpoint into a buffer of some sort, normally a window or a texture (a subclass of RenderTarget). OGRE cameras support both perspective projection (the default, meaning objects get smaller the further away they are) and orthographic projection (blueprint-style, no decrease in size with distance). Each camera carries with it a style of rendering, e.g. full textured, flat shaded, wireframe), field of view, rendering distances etc., allowing you to use OGRE to create complex multi-window views if required. In addition, more than one camera can point at a single render target if required, each rendering to a subset of the target, allowing split screen and picture-in-picture views.
Cameras maintain their own aspect ratios, field of view, and frustum, and project coordinates into a space measured from -1 to 1 in X and Y, and 0 to 1 in Z. At render time, the camera will be rendering to a viewport which will translate these parametric co-ordinates into real screen coordinates. Obviously it is advisable that the viewport has the same aspect ratio as the camera to avoid distortion (unless you want it!).
Note that a Camera can be attached to a SceneNode, using the method SceneNode::attachObject(). If this is done the Camera will combine it's own position/orientation settings with it's parent SceneNode. This is useful for implementing more complex Camera / object relationships i.e. having a camera attached to a world object.
