al_transform_coordinates_3d_projective(3)

NAME
       al_transform_coordinates_3d_projective - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro.h>

              void al_transform_coordinates_3d_projective(const ALLEGRO_TRANSFORM *trans,
                 float *x, float *y, float *z)


DESCRIPTION
       Transform x, y, z as homogeneous coordinates.  This is the same as
       using al_transform_coordinates_4d(3) with the w coordinate set to 1,
       then dividing x, y, z by the resulting w.  This will provide the same
       normalized coordinates Allegro will draw to when a projective transform
       is in effect as set with al_use_projection_transform(3).  To get the
       actual pixel coordinates from those translate and scale like so (w and
       h would be the pixel dimensions of the target bitmap):


              x = w / 2 + x * w / 2
              y = h / 2 - y * h / 2


       Parameters:

       o trans - Transformation to use

       o x, y, z - Pointers to the coordinates

       Example:


              ALLEGRO_TRANSFORM t2;
              al_copy_transform(&t2, al_get_current_transform());
              al_compose_transform(&t2, al_get_current_projection_transform());

              ALLEGRO_TRANSFORM t3;
              al_identity_transform(&t3);
              al_scale_transform(&t3, 0.5, -0.5);
              al_translate_transform(&t3, 0.5, 0.5);
              al_scale_transform(&t3, al_get_bitmap_width(al_get_target_bitmap()),
                                 al_get_bitmap_height(al_get_target_bitmap()));

              al_transform_coordinates_3d_projective(&t2, &x, &y, &z);
              // x, y now contain normalized coordinates
              al_transform_coordinates(&t3, &x, &y);
              // x, y now contain pixel coordinates


       Since 5.2.4

SEE ALSO
       al_use_transform(3), al_transform_coordinates(3),
       al_transform_coordinates_3d(3), al_use_projection_transform(3)

Allegro reference manual
                                     al_transform_coordinates_3d_projective(3)