NAME

       exquat - A comparison between Euler angles and quaternions. Allegro game programming library.

SYNOPSIS

       #include <allegro.h>

       Example exquat

DESCRIPTION

       Euler angles are convenient for storing and creating 3D orientations.  However, this program demonstrates
       that  they  are  not good when interpolating between two different orientations. The problem is solved by
       using Allegro's quaternion operations.

       In this program, two cubes are rotated between random orientations.  Notice that although they  have  the
       same beginning and ending orientations, they do not follow the same path between orientations.

       One  cube  is  being  rotated by directly incrementing or decrementing the Euler angles from the starting
       point to the ending point.  This is an intuitive notion, but it is incorrect because it  does  not  cause
       the  object  to turn around a single unchanging axis of rotation.  The axis of rotation wobbles resulting
       in the object spinning in strange ways. The object will eventually end up in  the  orientation  that  the
       user  intended,  but  it  gets  there  in a way that is unattractive.  Imagine if this method was used to
       update the position of a camera in a game! Sometimes it would swing wildly and disorient the player.

       The other cube is animated using quaternions. This results in a much more pleasing animation because  the
       cube turns around a single axis of rotation.

SEE ALSO

       BITMAP(3alleg4),   END_OF_MAIN(3alleg4),   MATRIX_f(3alleg4),   QUAT(3alleg4),   acquire_bitmap(3alleg4),
       allegro_error(3alleg4),   allegro_init(3alleg4),    allegro_message(3alleg4),    apply_matrix_f(3alleg4),
       blit(3alleg4),  circle(3alleg4),  clear_keybuf(3alleg4), clear_to_color(3alleg4), create_bitmap(3alleg4),
       desktop_palette(3alleg4),    destroy_bitmap(3alleg4),    font(3alleg4),     get_camera_matrix_f(3alleg4),
       get_rotation_matrix(3alleg4),         get_rotation_matrix_f(3alleg4),         get_rotation_quat(3alleg4),
       install_keyboard(3alleg4),       keypressed(3alleg4),        line(3alleg4),        matrix_mul_f(3alleg4),
       palette_color(3alleg4),   persp_project_f(3alleg4),  quat_interpolate(3alleg4),  quat_to_matrix(3alleg4),
       readkey(3alleg4),   release_bitmap(3alleg4),   rest(3alleg4),   screen(3alleg4),   set_gfx_mode(3alleg4),
       set_palette(3alleg4), set_projection_viewport(3alleg4), textout_ex(3alleg4)

Allegro                                           version 4.4.3                                  exquat(3alleg4)