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*OpenGL 1.1 for AIX: Reference Manual*

## gluPerspective Subroutine

### Purpose

Sets up a perspective projection matrix.

### Library

OpenGL C bindings library: **libGL.a**

### C Syntax

**void gluPerspective(GLdouble** *FieldOfViewY***, **
** GLdouble ***AspectRatio***, **
** GLdouble ***zNear***, **
** GLdouble ***zFar***)**

### Description

The **gluPerspective** subroutine specifies a viewing frustum into the world coordinate system. Generally, the *AspectRatio* used with this subroutine should match that of its associated viewport. For example, an aspect ratio value of *AspectRatio*=2.0 means the viewer's angle of view is twice as wide in *x* as it is in *y*. If the viewport is twice as wide as it is tall, it displays the image without distortion.

The matrix generated by the **gluPerspective** subroutine is multiplied by the current matrix just as if the **glMultMatrix** subroutine were called with the generated matrix. To load the perspective matrix onto the current matrix stack instead, precede the call to **gluPerspective** with a call to the **glLoadIdentity** subroutine.

### Parameters

*FieldOfViewY* |
Specifies the field of view angle (in degrees) in the y direction. |

*AspectRatio* |
Indicates the aspect ratio. This value determines the field of view in the *x* direction and is the ratio of *x* (width) to *y* (height). |

*zNear* |
Specifies the distance from the viewer to the closest clipping plane. This value must be positive. |

*zFar* |
Specifies the distance from the viewer to the farthest clipping plane. This value must be positive. |

### Files

**/usr/include/GL/gl.h** |
Contains C language constraints, variable type definitions, and ANSI function prototypes for OpenGL. |

### Related Information

The **glFrustum** subroutine, **glLoadIdentity** subroutine, **glMultMatrix** subroutine, **gluOrtho2D** subroutine.

OpenGL Overview.

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