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c++visual-studioopenglglut

Can't understand gluLookAt arguments

I'm learning OpenGL (glut) now. By using GL_Lines I draw cube, but it looks like square so I tries to use gluLookAt. I've been searching and experimenting but I can't understand how it works! Help please.

Solution

  • As described in the documentation

    C Specification

    void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ,
               GLdouble centerX, GLdouble centerY, GLdouble centerZ,
               GLdouble upX, GLdouble upY, GLdouble upZ);

    Parameters

    eyeX, eyeY, eyeZ
    Specifies the position of the eye point.

    centerX, centerY, centerZ
    Specifies the position of the reference point.

    upX, upY, upZ
    Specifies the direction of the up vector.

    Description

    gluLookAt creates a viewing matrix derived from an eye point, a reference point indicating the center of the scene, and an UP vector.

    The matrix maps the reference point to the negative z axis and the eye point to the origin. When a typical projection matrix is used, the center of the scene therefore maps to the center of the viewport. Similarly, the direction described by the UP vector projected onto the viewing plane is mapped to the positive y axis so that it points upward in the viewport. The UP vector must not be parallel to the line of sight from the eye point to the reference point.

    Borrowing the following image (source)

    enter image description here

    The eye would be P, the center would be fc, and up would be up. The "near plane" and "far plane" defined the extents of the viewing frustum