Curve Fitting: minor change to re-fitting method

Avoid calculating a new split-index when re-fitting.

While checking if a knot can be removed, the index with the highest error
can be used as a candidate to replace the knot
(in the case it can't be removed).

4 files changed, 80 insertions, 21 deletions

diff --git a/extern/curve_fit_nd/curve_fit_nd.h b/extern/curve_fit_nd/curve_fit_nd.h
index 7232f802e28..18244799b0f 100644
--- a/extern/curve_fit_nd/curve_fit_nd.h
+++ b/extern/curve_fit_nd/curve_fit_nd.h
@@ -36,7 +36,7 @@
 /* curve_fit_cubic.c */
 
 /**
- * Takes a flat array of points and evalues that to calculate a bezier spline.
+ * Takes a flat array of points and evaluates that to calculate a bezier spline.
  *
  * \param points, points_len: The array of points to calculate a cubics from.
  * \param dims: The number of dimensions for for each element in \a points.
@@ -82,7 +82,7 @@ int curve_fit_cubic_to_points_fl(
         unsigned int **r_corners_index_array, unsigned int *r_corners_index_len);
 
 /**
- * Takes a flat array of points and evalues that to calculate handle lengths.
+ * Takes a flat array of points and evaluates that to calculate handle lengths.
  *
  * \param points, points_len: The array of points to calculate a cubics from.
  * \param dims: The number of dimensions for for each element in \a points.
@@ -107,7 +107,8 @@ int curve_fit_cubic_to_points_single_db(
 
         double  r_handle_l[],
         double  r_handle_r[],
-        double *r_error_sq);
+        double *r_error_sq,
+        unsigned int *r_error_index);
 
 int curve_fit_cubic_to_points_single_fl(
         const float       *points,
@@ -120,7 +121,8 @@ int curve_fit_cubic_to_points_single_fl(
 
         float   r_handle_l[],
         float   r_handle_r[],
-        float  *r_error_sq);
+        float  *r_error_sq,
+        unsigned int *r_error_index);
 
 enum {
 	CURVE_FIT_CALC_HIGH_QUALIY          = (1 << 0),
diff --git a/extern/curve_fit_nd/intern/curve_fit_cubic.c b/extern/curve_fit_nd/intern/curve_fit_cubic.c
index 0a32f1e796a..ed855d34b08 100644
--- a/extern/curve_fit_nd/intern/curve_fit_cubic.c
+++ b/extern/curve_fit_nd/intern/curve_fit_cubic.c
@@ -554,8 +554,8 @@ static void cubic_from_points_fallback(
 	r_cubic->orig_span = (points_offset_len - 1);
 #endif
 
-	/* p1 = p0 - (tan_l * alpha_l);
-	 * p2 = p3 + (tan_r * alpha_r);
+	/* p1 = p0 - (tan_l * alpha);
+	 * p2 = p3 + (tan_r * alpha);
 	 */
 	msub_vn_vnvn_fl(p1, p0, tan_l, alpha, dims);
 	madd_vn_vnvn_fl(p2, p3, tan_r, alpha, dims);
@@ -1436,12 +1436,11 @@ int curve_fit_cubic_to_points_single_db(
 
         double  r_handle_l[],
         double  r_handle_r[],
-        double  *r_error_max_sq)
+        double *r_error_max_sq,
+        uint   *r_error_index)
 {
 	Cubic *cubic = alloca(cubic_alloc_size(dims));
 
-	uint split_index;
-
 	/* in this instance theres no advantage in using length cache,
 	 * since we're not recursively calculating values. */
 #ifdef USE_LENGTH_CACHE
@@ -1462,7 +1461,7 @@ int curve_fit_cubic_to_points_single_db(
 #endif
 	        tan_l, tan_r, error_threshold, dims,
 
-	        cubic, r_error_max_sq, &split_index);
+	        cubic, r_error_max_sq, r_error_index);
 
 #ifdef USE_LENGTH_CACHE
 	if (points_length_cache_alloc) {
@@ -1487,7 +1486,8 @@ int curve_fit_cubic_to_points_single_fl(
 
         float   r_handle_l[],
         float   r_handle_r[],
-        float  *r_error_sq)
+        float  *r_error_sq,
+        uint   *r_error_index)
 {
 	const uint points_flat_len = points_len * dims;
 	double *points_db = malloc(sizeof(double) * points_flat_len);
@@ -1521,7 +1521,8 @@ int curve_fit_cubic_to_points_single_fl(
 	        (double)error_threshold,
 	        tan_l_db, tan_r_db,
 	        r_handle_l_db, r_handle_r_db,
-	        &r_error_sq_db);
+	        &r_error_sq_db,
+	        r_error_index);
 
 	free(points_db);
 
diff --git a/extern/curve_fit_nd/intern/curve_fit_cubic_refit.c b/extern/curve_fit_nd/intern/curve_fit_cubic_refit.c
index bf1ab99995f..96ec9a33270 100644
--- a/extern/curve_fit_nd/intern/curve_fit_cubic_refit.c
+++ b/extern/curve_fit_nd/intern/curve_fit_cubic_refit.c
@@ -207,7 +207,7 @@ struct KnotCornerState {
 
 /* Utility functions */
 
-#ifdef USE_KNOT_REFIT
+#if defined(USE_KNOT_REFIT) && !defined(USE_KNOT_REFIT_REMOVE)
 /**
  * Find the most distant point between the 2 knots.
  */
@@ -269,7 +269,7 @@ static uint knot_find_split_point(
 
 	return split_point;
 }
-#endif  /* USE_KNOT_REFIT */
+#endif  /* USE_KNOT_REFIT && !USE_KNOT_REFIT_REMOVE */
 
 
 #ifdef USE_CORNER_DETECT
@@ -322,7 +322,7 @@ static double knot_remove_error_value(
         const double *points_offset_length_cache,
         const uint dims,
         /* Avoid having to re-calculate again */
-        double r_handle_factors[2])
+        double r_handle_factors[2], uint *r_error_index)
 {
 	double error_sq = FLT_MAX;
 
@@ -338,7 +338,7 @@ static double knot_remove_error_value(
 	        points_offset, points_offset_len, points_offset_length_cache, dims, 0.0,
 	        tan_l, tan_r,
 	        handle_factor_l, handle_factor_r,
-	        &error_sq);
+	        &error_sq, r_error_index);
 
 	assert(error_sq != FLT_MAX);
 
@@ -363,6 +363,7 @@ static double knot_calc_curve_error_value(
 	        ((knot_r->index + pd->points_len) - knot_l->index)) + 1;
 
 	if (points_offset_len != 2) {
+		uint error_index_dummy;
 		return knot_remove_error_value(
 		        tan_l, tan_r,
 		        &pd->points[knot_l->index * dims], points_offset_len,
@@ -372,7 +373,55 @@ static double knot_calc_curve_error_value(
 		        NULL,
 #endif
 		        dims,
-		        r_handle_factors);
+		        r_handle_factors, &error_index_dummy);
+	}
+	else {
+		/* No points between, use 1/3 handle length with no error as a fallback. */
+		assert(points_offset_len == 2);
+#ifdef USE_LENGTH_CACHE
+		r_handle_factors[0] = r_handle_factors[1] = pd->points_length_cache[knot_l->index] / 3.0;
+#else
+		r_handle_factors[0] = r_handle_factors[1] = len_vnvn(
+		        &pd->points[(knot_l->index + 0) * dims],
+		        &pd->points[(knot_l->index + 1) * dims], dims) / 3.0;
+#endif
+		return 0.0;
+	}
+}
+
+#ifdef USE_KNOT_REFIT_REMOVE
+
+static double knot_calc_curve_error_value_and_index(
+        const struct PointData *pd,
+        const struct Knot *knot_l, const struct Knot *knot_r,
+        const double *tan_l, const double *tan_r,
+        const uint dims,
+        double r_handle_factors[2],
+        uint *r_error_index)
+{
+	const uint points_offset_len = ((knot_l->index < knot_r->index) ?
+	        (knot_r->index - knot_l->index) :
+	        ((knot_r->index + pd->points_len) - knot_l->index)) + 1;
+
+	if (points_offset_len != 2) {
+		const double error_sq = knot_remove_error_value(
+		        tan_l, tan_r,
+		        &pd->points[knot_l->index * dims], points_offset_len,
+#ifdef USE_LENGTH_CACHE
+		        &pd->points_length_cache[knot_l->index],
+#else
+		        NULL,
+#endif
+		        dims,
+		        r_handle_factors, r_error_index);
+
+		/* Adjust the offset index to the global index & wrap if needed. */
+		*r_error_index += knot_l->index;
+		if (*r_error_index >= pd->points_len) {
+			*r_error_index -= pd->points_len;
+		}
+
+		return error_sq;
 	}
 	else {
 		/* No points between, use 1/3 handle length with no error as a fallback. */
@@ -384,9 +433,11 @@ static double knot_calc_curve_error_value(
 		        &pd->points[(knot_l->index + 0) * dims],
 		        &pd->points[(knot_l->index + 1) * dims], dims) / 3.0;
 #endif
+		*r_error_index = 0;
 		return 0.0;
 	}
 }
+#endif  /* USE_KNOT_REFIT_REMOVE */
 
 struct KnotRemove_Params {
 	Heap *heap;
@@ -556,15 +607,18 @@ static void knot_refit_error_recalculate(
 	assert(k->can_remove);
 
 #ifdef USE_KNOT_REFIT_REMOVE
+	(void)knots_len;
+
+	uint refit_index = SPLIT_POINT_INVALID;
 	{
 		double handles[2];
 
 		/* First check if we can remove, this allows to refit and remove as we go. */
-		const double cost_sq = knot_calc_curve_error_value(
+		const double cost_sq = knot_calc_curve_error_value_and_index(
 		        p->pd, k->prev, k->next,
 		        k->prev->tan[1], k->next->tan[0],
 		        dims,
-		        handles);
+		        handles, &refit_index);
 
 		if (cost_sq < error_sq_max) {
 			struct KnotRefitState *r;
@@ -598,13 +652,14 @@ static void knot_refit_error_recalculate(
 	}
 #else
 	(void)error_sq_max;
-#endif  /* USE_KNOT_REFIT_REMOVE */
 
 	const uint refit_index = knot_find_split_point(
 	         p->pd, k->prev, k->next,
 	         knots_len,
 	         dims);
 
+#endif  /* USE_KNOT_REFIT_REMOVE */
+
 	if ((refit_index == SPLIT_POINT_INVALID) ||
 	    (refit_index == k->index))
 	{
diff --git a/source/blender/editors/curve/editcurve.c b/source/blender/editors/curve/editcurve.c
index 648fe930030..a69264cd012 100644
--- a/source/blender/editors/curve/editcurve.c
+++ b/source/blender/editors/curve/editcurve.c
@@ -5850,6 +5850,7 @@ static int curve_dissolve_exec(bContext *C, wmOperator *UNUSED(op))
 					BLI_assert(points_stride + dims == points + (points_len * dims));
 
 					float tan_l[3], tan_r[3], error_sq_dummy;
+					unsigned int error_index_dummy;
 
 					sub_v3_v3v3(tan_l, bezt_prev->vec[1], bezt_prev->vec[2]);
 					normalize_v3(tan_l);
@@ -5860,7 +5861,7 @@ static int curve_dissolve_exec(bContext *C, wmOperator *UNUSED(op))
 					        points, points_len, NULL, dims, FLT_EPSILON,
 					        tan_l, tan_r,
 					        bezt_prev->vec[2], bezt_next->vec[0],
-					        &error_sq_dummy);
+					        &error_sq_dummy, &error_index_dummy);
 
 					if (!ELEM(bezt_prev->h2, HD_FREE, HD_ALIGN)) {
 						bezt_prev->h2 = (bezt_prev->h2 == HD_VECT) ? HD_FREE : HD_ALIGN;