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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
This commit is contained in:
Mattias Fredriksson 2022-11-14 18:20:32 -06:00 committed by Hans Goudey
parent 18af9da572
commit b28348f9e9
Notes: blender-bot 2024-04-29 13:07:32 +02:00 
Referenced by issue #102428, Regression set spline cyclic geometry glitch.
1 changed files with 78 additions and 17 deletions
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95
source/blender/geometry/intern/trim_curves.cc
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@ -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) {
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());
/* 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];
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);
/* 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});
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;