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.TH "al_transform_coordinates_3d_projective" "3alleg5" "" "Allegro reference manual" ""
.hy
.SH NAME
.PP
al_transform_coordinates_3d_projective - Allegro 5 API
.SH SYNOPSIS
.IP
.nf
\f[C]
#include <allegro5/allegro.h>

void al_transform_coordinates_3d_projective(const ALLEGRO_TRANSFORM *trans,
   float *x, float *y, float *z)
\f[R]
.fi
.SH DESCRIPTION
.PP
Transform x, y, z as homogeneous coordinates.
This is the same as using al_transform_coordinates_4d(3alleg5) 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(3alleg5).
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
.nf
\f[C]
x = w / 2 + x * w / 2
y = h / 2 - y * h / 2
\f[R]
.fi
.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
.nf
\f[C]
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
\f[R]
.fi
.PP
Since 5.2.4
.SH SEE ALSO
.PP
al_use_transform(3alleg5), al_transform_coordinates(3alleg5),
al_transform_coordinates_3d(3alleg5),
al_use_projection_transform(3alleg5)