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.TH "al_transform_coordinates_3d_projective" "3" "" "Allegro reference manual"
.SH NAME
al_transform_coordinates_3d_projective \- Allegro 5 API
.SH SYNOPSIS
.IP
.EX
#include \f[B]<allegro5/allegro.h>\f[R]

void al_transform_coordinates_3d_projective(const ALLEGRO_TRANSFORM *trans,
   float *x, float *y, float *z)
.EE
.SH 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):
.IP
.EX
x = w / 2 + x * w / 2
y = h / 2 \- y * h / 2
.EE
.PP
\f[I]Parameters:\f[R]
.IP \[bu] 2
trans \- Transformation to use
.IP \[bu] 2
x, y, z \- Pointers to the coordinates
.PP
Example:
.IP
.EX
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);
\f[I]// x, y now contain normalized coordinates\f[R]
al_transform_coordinates(&t3, &x, &y);
\f[I]// x, y now contain pixel coordinates\f[R]
.EE
.PP
Since 5.2.4
.SH SEE ALSO
al_use_transform(3), al_transform_coordinates(3),
al_transform_coordinates_3d(3), al_use_projection_transform(3)