[Bf-blender-cvs] [b28348f9e97] blender-v3.4-release: Partial Fix T102428: Invertible Bezier curve trim within one segment

[Mattias Fredriksson]

Commit: b28348f9e972cd472f8e72c2cfcc77cd5ac12d10
Author: Mattias Fredriksson
Date:   Mon Nov 14 18:20:32 2022 -0600
Branches: blender-v3.4-release
https://developer.blender.org/rBb28348f9e972cd472f8e72c2cfcc77cd5ac12d10

Partial Fix T102428: Invertible Bezier curve trim within one segment

Adjusts behavior for trimming Bezier curves, specifically the outer
Bezier handles for the endpoints which do not influence the actual
curve. Handles are only adjusted if they lie within the same segment
with at most one endpoint being a control point (unless they are the
same in which handles are set to the point itself). The result yields
a curve in which the trim result can be inverted by re-setting the
cyclic property for the curve using 'Set Spline Cyclic' node
(iff both trim endpoints lie within a segment).

Differential Revision: https://developer.blender.org/D16488

===================================================================

M	source/blender/geometry/intern/trim_curves.cc

===================================================================

diff --git a/source/blender/geometry/intern/trim_curves.cc b/source/blender/geometry/intern/trim_curves.cc
index 1aff07f2b4e..e8f2c859f18 100644
--- a/source/blender/geometry/intern/trim_curves.cc
+++ b/source/blender/geometry/intern/trim_curves.cc
@@ -232,7 +232,7 @@ static int64_t copy_point_data_between_endpoints(const Span<T> src_data,
     dst_index += increment;
   }
   else {
-    increment = src_range.one_after_last() - src_range.first();
+    increment = src_range.one_after_last() - int64_t(src_range.first());
     dst_data.slice(dst_index, increment).copy_from(src_data.slice(src_range.first(), increment));
     dst_index += increment;
   }
@@ -464,37 +464,98 @@ static void sample_interval_bezier(const Span<float3> src_positions,
 
   if (start_point_trimmed) {
     dst_handles_l[dst_range.first() + 1] = start_point_insert.handle_next;
-    /* No need to set handle type (remains the same)! */
+    /* No need to change handle type (remains the same). */
   }
 
   /* Handle 'end_point' */
   bke::curves::bezier::Insertion end_point_insert;
-  if (end_point.is_controlpoint()) {
-    /* Do nothing, the 'end_point' control point is included in the copy iteration. */
+  if (end_point.parameter == 0.0f) {
+    if (end_point.index == start_point.index) {
+      /* Start point is same point or in the same segment. */
+      if (start_point.parameter == 0.0f) {
+        /* Same point. */
+        BLI_assert(dst_range.size() == 1LL + src_range.size_range());
+        dst_handles_l[dst_range.first()] = dst_positions[dst_range.first()];
+        dst_handles_r[dst_range.last()] = dst_positions[dst_range.first()];
+      }
+      else if (start_point.parameter == 1.0f) {
+        /* Start is next controlpoint, do nothing. */
+      }
+      else {
+        /* Within the segment. */
+        BLI_assert(dst_range.size() == 1LL + src_range.size_range() || dst_range.size() == 2);
+        dst_handles_r[dst_range.last()] = start_point_insert.handle_prev;
+      }
+    }
+    /* Start point is considered 'before' the endpoint and ignored. */
+  }
+  else if (end_point.parameter == 1.0f) {
+    if (end_point.next_index == start_point.index) {
+      /* Start point is same or in 'next' segment. */
+      if (start_point.parameter == 0.0f) {
+        /* Same point */
+        BLI_assert(dst_range.size() == 1LL + src_range.size_range());
+        dst_handles_l[dst_range.first()] = dst_positions[dst_range.first()];
+        dst_handles_r[dst_range.last()] = dst_positions[dst_range.first()];
+      }
+      else if (start_point.parameter == 1.0f) {
+        /* Start is next controlpoint, do nothing. */
+      }
+      else {
+        /* In next segment. */
+        BLI_assert(dst_range.size() == 1LL + src_range.size_range() || dst_range.size() == 2);
+        dst_handles_r[dst_range.last()] = start_point_insert.handle_prev;
+      }
+    }
   }
   else {
     /* Trimmed in both ends within the same (and only) segment! Ensure both end points is not a
      * loop. */
-    if (start_point_trimmed && start_point.index == end_point.index &&
-        start_point.parameter <= end_point.parameter) {
-
-      /* Copy following segment control point. */
-      dst_positions[dst_index] = src_positions[end_point.next_index];
-      dst_handles_r[dst_index] = src_handles_r[end_point.next_index];
-
-      /* Compute interpolation in the result curve. */
-      const float parameter = (end_point.parameter - start_point.parameter) /
-                              (1.0f - start_point.parameter);
-      end_point_insert = knot_insert_bezier(
-          dst_positions,
-          dst_handles_l,
-          dst_handles_r,
-          {{int(dst_range.first()), int(dst_range.first() + 1)}, parameter});
+    if (start_point.index == end_point.index && start_point.parameter < 1.0f) {
+      BLI_assert(dst_range.size() == 2 || dst_range.size() == 2ll + src_range.size_range() ||
+                 dst_range.size() == 1LL + src_range.size_range());
+
+      if (start_point.parameter > end_point.parameter && start_point.parameter < 1.0f) {
+        /* Start point comes after the endpoint within the segment. */
+        BLI_assert(end_point.parameter >= 0.0f);
+
+        const float parameter = end_point.parameter / start_point.parameter;
+        end_point_insert = bke::curves::bezier::insert(dst_positions[dst_index - 1],
+                                                       start_point_insert.handle_prev,
+                                                       start_point_insert.left_handle,
+                                                       start_point_insert.position,
+                                                       parameter);
+
+        /* Update startpoint handle. */
+        dst_handles_l[dst_range.first()] = end_point_insert.handle_next;
+      }
+      else {
+        /* Start point lies before the endpoint within the segment. */
+
+        const float parameter = (end_point.parameter - start_point.parameter) /
+                                (1.0f - start_point.parameter);
+        /* Unused only when parameter == 0.0f! */
+        const float3 handle_next = start_point.parameter == 0.0f ?
+                                       src_handles_l[end_point.next_index] :
+                                       start_point_insert.handle_next;
+        end_point_insert = bke::curves::bezier::insert(dst_positions[dst_index - 1],
+                                                       dst_handles_r[dst_index - 1],
+                                                       handle_next,
+                                                       src_positions[end_point.next_index],
+                                                       parameter);
+      }
     }
     else {
       /* General case, compute the insertion point.  */
       end_point_insert = knot_insert_bezier(
           src_positions, src_handles_l, src_handles_r, end_point);
+
+      if ((start_point.parameter >= end_point.parameter && end_point.index == start_point.index) ||
+          (start_point.parameter == 0.0f && end_point.next_index == start_point.index)) {
+        /* Start point is next controlpoint. */
+        dst_handles_l[dst_range.first()] = end_point_insert.handle_next;
+        /* No need to change handle type (remains the same). */
+      }
     }
 
     dst_handles_r[dst_index - 1] = end_point_insert.handle_prev;