Implement segmenting of Line2D for better fidelity when using width c…

…urves

doc/classes/Line2D.xml

@@ -70,6 +70,9 @@
  [b]Note:[/b] The shape of the closing segment is not guaranteed to be seamless if a [member width_curve] is provided.
  [b]Note:[/b] The joint between the closing segment and the first segment is drawn first and it samples the [member gradient] and the [member width_curve] at the beginning. This is an implementation detail that might change in a future version.
  </member>
+ <member name="curve_offset" type="float" setter="set_curve_offset" getter="get_curve_offset" default="0.0">
+ The horizontal offset value used when sampling from the width curve. Typically ranges from -1.0 to 1.0.
+ </member>
  <member name="default_color" type="Color" setter="set_default_color" getter="get_default_color" default="Color(1, 1, 1, 1)">
  The color of the polyline. Will not be used if a gradient is set.
  </member>

scene/2d/line_2d.cpp

@@ -119,6 +119,11 @@ Ref<Curve> Line2D::get_curve() const {
  return _curve;
 }
 
+void Line2D::set_curve_offset(float curve_offset) {
+ _curve_offset = curve_offset;
+ queue_redraw();
+}
+
 Vector<Vector2> Line2D::get_points() const {
  return _points;
 }
@@ -277,9 +282,61 @@ void Line2D::_draw() {
  }
 
  // TODO Maybe have it as member rather than copying parameters and allocating memory?
+
+ int num_segments = _curve.is_valid() ? _curve->get_bake_resolution() : -1;
+ if (static_cast<int>(_generated_draw_points.get_capacity()) < num_segments)
+ _generated_draw_points.reserve(num_segments);
+ _generated_draw_points.clear();
+
+ bool just_use_points = num_segments == -1;
+ // We have less segments than what's defined, so we just use the points.
+ if (just_use_points) {
+ _generated_draw_points = _points;
+ } else {
+ // Set the first and last points from our line data.
+ _generated_draw_points.push_back(_points[0]);
+
+ // TODO: Cache the memory somewhere so we don't keep allocating memory
+ int line_count = _closed ? len : len - 1;
+ LocalVector<float> dists_between_points;
+ LocalVector<Vector2> line_directions;
+ dists_between_points.reserve(line_count);
+ line_directions.reserve(line_count);
+
+ // Gather the total line length, with distances and directions for each sub-line
+ float total_line_length = 0.0f;
+ for (int i = 0; i < line_count; ++i) {
+ Vector2 line_dir = _points[(i + 1) % len] - _points[i];
+ float distance_bt_points = line_dir.length();
+ total_line_length += distance_bt_points;
+ dists_between_points.push_back(distance_bt_points);
+ line_directions.push_back(line_dir / distance_bt_points);
+ }
+
+ // Can't have negative segments!
+ float segment_length = total_line_length / MAX(1, static_cast<float>(num_segments));
+ for (int s = 0; s < line_count; ++s) {
+ int segments_for_line = static_cast<int>(Math::ceil(dists_between_points[s] / segment_length));
+
+ Vector2 line_start = _points[s];
+ Vector2 line_end = _points[(s + 1) % len];
+ float line_distance = dists_between_points[s];
+ _generated_draw_points.push_back(_points[s]);
+
+ if (segments_for_line > 1) {
+ for (int l = 1; l < segments_for_line; ++l) {
+ float current_length_from_line_start = segment_length * static_cast<float>(l);
+ _generated_draw_points.push_back(line_start + (line_end - line_start) * (current_length_from_line_start / line_distance));
+ }
+ }
+ }
+ // Set last point.
+ _generated_draw_points.push_back(_points[line_count % len]);
+ }
+
  LineBuilder lb;
- lb.points = _points;
- lb.closed = _closed;
+ lb.closed = _closed && just_use_points;
+ lb.points = &_generated_draw_points;
  lb.default_color = _default_color;
  lb.gradient = *_gradient;
  lb.texture_mode = _texture_mode;
@@ -290,6 +347,7 @@ void Line2D::_draw() {
  lb.sharp_limit = _sharp_limit;
  lb.width = _width;
  lb.curve = *_curve;
+ lb.curve_offset = _curve_offset;
 
  RID texture_rid;
  if (_texture.is_valid()) {
@@ -358,6 +416,9 @@ void Line2D::_bind_methods() {
  ClassDB::bind_method(D_METHOD("set_curve", "curve"), &Line2D::set_curve);
  ClassDB::bind_method(D_METHOD("get_curve"), &Line2D::get_curve);
 
+ ClassDB::bind_method(D_METHOD("set_curve_offset", "curve_offset"), &Line2D::set_curve_offset);
+ ClassDB::bind_method(D_METHOD("get_curve_offset"), &Line2D::get_curve_offset);
+
  ClassDB::bind_method(D_METHOD("set_default_color", "color"), &Line2D::set_default_color);
  ClassDB::bind_method(D_METHOD("get_default_color"), &Line2D::get_default_color);
 
@@ -392,6 +453,7 @@ void Line2D::_bind_methods() {
  ADD_PROPERTY(PropertyInfo(Variant::BOOL, "closed"), "set_closed", "is_closed");
  ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "width", PROPERTY_HINT_NONE, "suffix:px"), "set_width", "get_width");
  ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "width_curve", PROPERTY_HINT_RESOURCE_TYPE, "Curve"), "set_curve", "get_curve");
+ ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "curve_offset", PROPERTY_HINT_RANGE, "-1.0,1.0,0.01"), "set_curve_offset", "get_curve_offset");
  ADD_PROPERTY(PropertyInfo(Variant::COLOR, "default_color"), "set_default_color", "get_default_color");
  ADD_GROUP("Fill", "");
  ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "gradient", PROPERTY_HINT_RESOURCE_TYPE, "Gradient"), "set_gradient", "get_gradient");

scene/2d/line_2d.h

@@ -85,6 +85,9 @@ class Line2D : public Node2D {
  void set_curve(const Ref<Curve> &curve);
  Ref<Curve> get_curve() const;
 
+ void set_curve_offset(float curve_offset);
+ float get_curve_offset() const { return _curve_offset; }
+
  void set_default_color(Color color);
  Color get_default_color() const;
 
@@ -127,12 +130,14 @@ class Line2D : public Node2D {
 
 private:
  Vector<Vector2> _points;
+ LocalVector<Vector2> _generated_draw_points;
  LineJointMode _joint_mode = LINE_JOINT_SHARP;
  LineCapMode _begin_cap_mode = LINE_CAP_NONE;
  LineCapMode _end_cap_mode = LINE_CAP_NONE;
  bool _closed = false;
  float _width = 10.0;
  Ref<Curve> _curve;
+ float _curve_offset = 0.0f;
  Color _default_color = Color(1, 1, 1);
  Ref<Gradient> _gradient;
  Ref<Texture2D> _texture;

scene/2d/line_builder.cpp

@@ -44,7 +44,7 @@ LineBuilder::LineBuilder() {
 
 void LineBuilder::build() {
  // Need at least 2 points to draw a line, so clear the output and return.
- if (points.size() < 2) {
+ if (points->size() < 2) {
  vertices.clear();
  colors.clear();
  indices.clear();
@@ -57,7 +57,7 @@ void LineBuilder::build() {
  const float hw = width / 2.f;
  const float hw_sq = hw * hw;
  const float sharp_limit_sq = sharp_limit * sharp_limit;
- const int point_count = points.size();
+ const int point_count = static_cast<int>(points->size());
  const bool wrap_around = closed && point_count > 2;
 
  _interpolate_color = gradient != nullptr;
@@ -68,8 +68,8 @@ void LineBuilder::build() {
 
  // Initial values
 
- Vector2 pos0 = points[0];
- Vector2 pos1 = points[1];
+ Vector2 pos0 = (*points)[0];
+ Vector2 pos1 = (*points)[1];
  Vector2 f0 = (pos1 - pos0).normalized();
  Vector2 u0 = f0.orthogonal();
  Vector2 pos_up0 = pos0;
@@ -92,10 +92,10 @@ void LineBuilder::build() {
  if (distance_required) {
  // Calculate the total distance.
  for (int i = 1; i < point_count; ++i) {
- total_distance += points[i].distance_to(points[i - 1]);
+ total_distance += (*points)[i].distance_to((*points)[i - 1]);
  }
  if (wrap_around) {
- total_distance += points[point_count - 1].distance_to(pos0);
+ total_distance += (*points)[point_count - 1].distance_to(pos0);
  } else {
  // Adjust the total distance.
  // The line's outer length may be a little higher due to the end caps.
@@ -172,8 +172,8 @@ void LineBuilder::build() {
 
  // For each additional segment
  for (int i = first_point; i <= segments_count; ++i) {
- pos1 = points[(i == -1) ? point_count - 1 : i % point_count]; // First point.
- Vector2 pos2 = points[(i + 1) % point_count]; // Second point.
+ pos1 = (*points)[(i == -1) ? point_count - 1 : i % point_count]; // First point.
+ Vector2 pos2 = (*points)[(i + 1) % point_count]; // Second point.
 
  Vector2 f1 = (pos2 - pos1).normalized();
  Vector2 u1 = f1.orthogonal();
@@ -189,7 +189,8 @@ void LineBuilder::build() {
  color1 = gradient->get_color_at_offset(current_distance1 / total_distance);
  }
  if (retrieve_curve) {
- width_factor = curve->sample_baked(current_distance1 / total_distance);
+ float offset = CLAMP((current_distance1 / total_distance) - curve_offset, 0.0f, 1.0f);
+ width_factor = curve->sample_baked(offset);
  modified_hw = hw * width_factor;
  }
 
@@ -379,7 +380,7 @@ void LineBuilder::build() {
 
  // Draw the last (or only) segment, with its end cap logic.
  if (!wrap_around) {
- pos1 = points[point_count - 1];
+ pos1 = (*points)[point_count - 1];
 
  if (distance_required) {
  current_distance1 += pos0.distance_to(pos1);

scene/2d/line_builder.h

@@ -37,13 +37,14 @@ class LineBuilder {
 public:
  // TODO Move in a struct and reference it
  // Input
- Vector<Vector2> points;
+ LocalVector<Vector2> *points;
  Line2D::LineJointMode joint_mode = Line2D::LINE_JOINT_SHARP;
  Line2D::LineCapMode begin_cap_mode = Line2D::LINE_CAP_NONE;
  Line2D::LineCapMode end_cap_mode = Line2D::LINE_CAP_NONE;
  bool closed = false;
  float width = 10.0;
  Curve *curve = nullptr;
+ float curve_offset = 0.0f;
  Color default_color = Color(0.4, 0.5, 1);
  Gradient *gradient = nullptr;
  Line2D::LineTextureMode texture_mode = Line2D::LineTextureMode::LINE_TEXTURE_NONE;