bionic (3) exquat.3alleg4.gz

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)