quat_interpolate(3alleg4) [opendarwin man page]

quat_interpolate(3alleg4)					  Allegro manual					 quat_interpolate(3alleg4)

NAME

       quat_interpolate - Constructs a quaternion representing a rotation between from and to. Allegro game programming library.

SYNOPSIS

       #include <allegro.h>

       void quat_interpolate(const QUAT *from, const QUAT *to, float t, QUAT *out);

DESCRIPTION

       Constructs  a  quaternion  that	represents  a rotation between from and to.  The argument t can be anything between 0 and 1 and represents
       where between from and to the result will be. 0 returns from, 1 returns to, and 0.5 will return a rotation exactly in between.  The  result
       is copied to out. This function will create the short rotation (less than 180 degrees) between from and to.

SEE ALSO

       exquat(3alleg4)

Allegro 							   version 4.4.2					 quat_interpolate(3alleg4)

exquat(3alleg4) 						  Allegro manual						   exquat(3alleg4)

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  orienta-
       tions, 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),   alle-
       gro_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_cam-
       era_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_pal-
       ette(3alleg4), set_projection_viewport(3alleg4), textout_ex(3alleg4)

Allegro 							   version 4.4.2						   exquat(3alleg4)