diff options
| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | src/cairo-arc.c | 20 |
2 files changed, 11 insertions, 14 deletions
@@ -1,5 +1,10 @@ 2005-08-22 Bertram Felgenhauer <int-e@gmx.de> + * src/cairo-arc.c (_arc_segments_needed): correct the calculation of + the error bound. + +2005-08-22 Bertram Felgenhauer <int-e@gmx.de> + * src/cairo-pen.c (_cairo_pen_vertices_needed): use new function. strip comment of derivation for major axis length. diff --git a/src/cairo-arc.c b/src/cairo-arc.c index e9f35993..4b767f17 100644 --- a/src/cairo-arc.c +++ b/src/cairo-arc.c @@ -100,27 +100,19 @@ _arc_max_angle_for_tolerance_normalized (double tolerance) return angle; } -/* XXX: The computation here if bogus. Correct math (with proof!) is - * available in _cairo_pen_vertices_needed. */ static int _arc_segments_needed (double angle, double radius, cairo_matrix_t *ctm, double tolerance) { - double l1, l2, lmax; - double max_angle; + double major_axis, max_angle; - _cairo_matrix_compute_eigen_values (ctm, &l1, &l2); - - l1 = fabs (l1); - l2 = fabs (l2); - if (l1 > l2) - lmax = l1; - else - lmax = l2; - - max_angle = _arc_max_angle_for_tolerance_normalized (tolerance / (radius * lmax)); + /* the error is amplified by at most the length of the + * major axis of the circle; see cairo-pen.c for a more detailed analysis + * of this. */ + major_axis = _cairo_matrix_transformed_circle_major_axis (ctm, radius); + max_angle = _arc_max_angle_for_tolerance_normalized (tolerance / major_axis); return (int) ceil (angle / max_angle); } |