MirBSD manpage: gluLookAt(3)

```
GLULOOKAT(3G)       UNIX Programmer's Manual        GLULOOKAT(3G)
```

NAME

```     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
| centerY   -
| centerZ   -   eyeX  |
-   eyeY  |
eyeZ  |
|

Let UP be the vector (upX,upY,upZ).
_____
Then normalize as follows: f = ||F||

MirBSD #10-current     Printed 2021-12-07                       1

GLULOOKAT(3G)       UNIX Programmer's Manual        GLULOOKAT(3G)

___P___
UP' = ||UP||

Finally, let s = f x UP', and u = s x f.

M is then constructed as follows:
|
|
M = | s[0]
| u[0]
|-f[0]   s[1]
|  0     u[1]
-f[1]   s[2]
0     u[2]
-f[2]  0  |
0    0  |
0  |
1  |
|
|
and gluLookAt is equivalent to glMultMatrixf(M);
glTranslated (-eyex, -eyey, -eyez);
```

```     glFrustum(3G), gluPerspective(3G)