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app: add gimp_coords_interpolate_bezier_at() 

... which calculates the position and/or velocity of a Bezier curve
at a given point.
This commit is contained in:
Ell 2018-02-01 11:23:51 -05:00
parent 275815c808
commit ea34bbc92b
2 changed files with 60 additions and 10 deletions
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45
app/core/gimpcoords-interpolate.c
View File

@ -154,6 +154,51 @@ gimp_coords_interpolate_bezier_internal (const GimpCoords bezier_pt[4],
}
/*
* Returns the position and/or velocity of a Bezier curve at time 't'.
*/
void
gimp_coords_interpolate_bezier_at (const GimpCoords bezier_pt[4],
gdouble t,
GimpCoords *position,
GimpCoords *velocity)
{
gdouble u = 1.0 - t;
g_return_if_fail (bezier_pt != NULL);
if (position)
{
GimpCoords a;
GimpCoords b;
gimp_coords_mix ( u * u * u, &bezier_pt[0],
3.0 * u * u * t, &bezier_pt[1],
&a);
gimp_coords_mix (3.0 * u * t * t, &bezier_pt[2],
t * t * t, &bezier_pt[3],
&b);
gimp_coords_add (&a, &b, position);
}
if (velocity)
{
GimpCoords a;
GimpCoords b;
gimp_coords_mix (-3.0 * u * u, &bezier_pt[0],
3.0 * (u - 2.0 * t) * u, &bezier_pt[1],
&a);
gimp_coords_mix (-3.0 * (t - 2.0 * u) * t, &bezier_pt[2],
3.0 * t * t, &bezier_pt[3],
&b);
gimp_coords_add (&a, &b, velocity);
}
}
/*
* a helper function that determines if a bezier segment is "straight
* enough" to be approximated by a line.

25
app/core/gimpcoords-interpolate.h
View File

@ -20,17 +20,22 @@
#ifndef __GIMP_COORDS_INTERPOLATE_H__
#define __GIMP_COORDS_INTERPOLATE_H__
void gimp_coords_interpolate_bezier (const GimpCoords bezier_pt[4],
gdouble precision,
GArray *ret_coords,
GArray *ret_params);
void gimp_coords_interpolate_bezier (const GimpCoords bezier_pt[4],
gdouble precision,
GArray *ret_coords,
GArray *ret_params);
gboolean gimp_coords_bezier_is_straight (const GimpCoords bezier_pt[4],
gdouble precision);
void gimp_coords_interpolate_bezier_at (const GimpCoords bezier_pt[4],
gdouble t,
GimpCoords *position,
GimpCoords *velocity);
void gimp_coords_interpolate_catmull (const GimpCoords catmull_pt[4],
gdouble precision,
GArray *ret_coords,
GArray *ret_params);
gboolean gimp_coords_bezier_is_straight (const GimpCoords bezier_pt[4],
gdouble precision);
void gimp_coords_interpolate_catmull (const GimpCoords catmull_pt[4],
gdouble precision,
GArray *ret_coords,
GArray *ret_params);
#endif /* __GIMP_COORDS_INTERPOLATE_H__ */