Gambas Documentation - /comp/gb.opengl.glu/glu/lookat

# Glu.LookAt (gb.opengl.glu)

Static Sub LookAt ( EyeX As Float, EyeY As Float, EyeZ As Float, CenterX As Float, CenterY As Float, CenterZ As Float, UpX As Float, UpY As Float, UpZ As Float )

Define a viewing transformation.

### 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

Glu.LookAt 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 .

Then normalize as follows: f `` F F

UP ″ `` UP UP

Finally, let s `` f × UP ″ , and u `` s × f .

M is then constructed as follows: M `` s ⁡ 0 s ⁡ 1 s ⁡ 2 0 u ⁡ 0 u ⁡ 1 u ⁡ 2 0 - f ⁡ 0 - f ⁡ 1 - f ⁡ 2 0 0 0 0 1

and Glu.LookAt is equivalent to

    glMultMatrixf(M);
    glTranslated(-eyex, -eyey, -eyez);

### See also

- Glu.Perspective,

- Gl.Frustum

See original documentation on OpenGL website