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gluLookAt

Chapter 10

269

gluLookAt

gluLookAt: deﬁne a viewing transformation.

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.

Let

F = (centerx - eyex, centery - eyey, centerz- eyez), let up be the vector (upX, upY, upZ),

and then normalize as follows:

and

Finally, let s = f × up, and u = s × f.

M is then constructed as follows:

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