set_projection_viewport - Sets the viewport used to scale the output of persp_project(). Allegro game

       Sets the viewport used to scale the output of the persp_project() function. Pass the  dimensions  of  the
       screen  area  you  want  to  draw  onto, which will typically be 0, 0, SCREEN_W, and SCREEN_H. Also don't
       forget to pass an appropriate aspect ratio to get_camera_matrix later. The width and height  you  specify
       here  will  determine  how  big your viewport is in 3d space. So if an object in your 3D space is w units
       wide, it will fill the complete screen when you run into it (i.e., if it has a distance of 1.0 after  the
       camera  matrix  was  applied.  The  fov  and aspect-ratio parameters to get_camera_matrix also apply some
       scaling though, so this isn't always completely true). If you pass  -1/-1/2/2  as  parameters,  no  extra
       scaling will be performed by the projection.

       set_projection_viewport  -  Sets  the  viewport used to scale the output of persp_project(). Allegro game
       programming library.

persp_project(3alleg4),  get_camera_matrix(3alleg4),  ex3d(3alleg4),  excamera(3alleg4), exquat(3alleg4),
       exscn3d(3alleg4), exstars(3alleg4), exzbuf(3alleg4)

Allegro                                           version 4.4.3                 set_projection_viewport(3alleg4)

#include<allegro.h>voidset_projection_viewport(intx,inty,intw,inth);