The “Camera OpenGL” is the virtual position of a viewer in an OpenGL scene. It is defined by the viewer’s position and determines what is rendered on the display device. The camera is controlled by two matrices, the modelview and projection matrices, and can be moved within a scene. The projection matrix controls the camera’s attributes, such as perspective and focal length. Understanding the camera can be difficult, as it requires proficiency in matrix math and the OpenGL transformation pipeline.
“Camera OpenGL®” is the name given to the virtual position of a viewer within an Open Graphics Library® (OpenGL®) scene. It is defined by the viewer’s position within the scene and therefore by the position or direction in which they are looking. The position of the camera in an OpenGL® scene will determine what portion of a scene is rendered on the display device and at what angle. Two matrices are used to describe an OpenGL® camera: the modelview matrix and the projection matrix, which respectively describe the position of the camera and the way in which the objects it is looking at are displayed. A camera can be moved within a scene to show different areas or to simulate movement, although in many cases it is easier or more efficient to move objects in a scene instead of the camera.
When learning OpenGL®, some programmers have difficulty understanding the relatively abstract properties of an OpenGL® camera. This is largely because some transforms and other functions don’t work the same way on a camera as they do on a standard OpenGL® object. Additionally, complex operations with an OpenGL® camera usually require proficiency with matrix math and an understanding of the OpenGL® transformation pipeline. There are some useful features in supporting the OpenGL® libraries, although it can be difficult to rely solely on the support toolkits in more interactive applications.
The position of an OpenGL® camera is defined using the modelview matrix. The camera can be positioned anywhere within a scene and translated or rotated along any axis. In many applications, especially applications that contain only a handful of objects, it can be easier to reverse transform objects within a scene to give the impression of motion. Essentially, in this case, the entire scene moves around a static camera. For larger scenes, it may be easier to deal with the intricacies of pipeline and matrix math to move the camera freely, while leaving the scene static.
The attributes of an OpenGL® camera are controlled by the projection matrix. To use the camera analogy, the projection matrix can be thought of as the type of lens used. The projection matrix is frequently modified to create orthographic projections, which have no perspective adjustment, and perspective projections which take distance into account in determining the size of objects. Other effects, such as a fish-eye lens, focal length or different aspect ratios, can be set through the use of the projection matrix.
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