Added Line2D node that draws a polygon-based line

It supports unlimited width, color gradient, texture and some geometry
options for joints and caps. Also transparency without artifacts
(provided that line joints aren't too sharp).

4 files changed, 1026 insertions, 0 deletions

diff --git a/scene/2d/line_2d.cpp b/scene/2d/line_2d.cpp
new file mode 100644
index 0000000000..9db3659133
--- /dev/null
+++ b/scene/2d/line_2d.cpp
@@ -0,0 +1,307 @@
+#include "line_2d.h"
+#include "core_string_names.h"
+
+
+// Needed so we can bind functions
+VARIANT_ENUM_CAST(LineJointMode)
+VARIANT_ENUM_CAST(LineCapMode)
+VARIANT_ENUM_CAST(LineTextureMode)
+
+
+Line2D::Line2D() : Node2D() {
+	_joint_mode = LINE_JOINT_SHARP;
+	_begin_cap_mode = LINE_CAP_NONE;
+	_end_cap_mode = LINE_CAP_NONE;
+	_width = 10;
+	_default_color = Color(0.4,0.5,1);
+	_sharp_limit = 2.f;
+	_round_precision = 8;
+}
+
+void Line2D::set_points(const PoolVector<Vector2> &p_points) {
+	_points = p_points;
+	update();
+}
+
+void Line2D::set_width(float width) {
+	if(width < 0.0)
+		width = 0.0;
+	_width = width;
+	update();
+}
+
+float Line2D::get_width() const {
+	return _width;
+}
+
+PoolVector<Vector2> Line2D::get_points() const {
+	return _points;
+}
+
+void Line2D::set_point_pos(int i, Vector2 pos) {
+	_points.set(i, pos);
+	update();
+}
+
+Vector2 Line2D::get_point_pos(int i) const {
+	return _points.get(i);
+}
+
+int Line2D::get_point_count() const {
+	return _points.size();
+}
+
+void Line2D::add_point(Vector2 pos) {
+	_points.append(pos);
+	update();
+}
+
+void Line2D::remove_point(int i) {
+	_points.remove(i);
+	update();
+}
+
+void Line2D::set_default_color(Color color) {
+	_default_color = color;
+	update();
+}
+
+Color Line2D::get_default_color() const {
+	return _default_color;
+}
+
+void Line2D::set_gradient(const Ref<ColorRamp>& gradient) {
+
+	// Cleanup previous connection if any
+	if(_gradient.is_valid()) {
+		(**_gradient).disconnect(CoreStringNames::get_singleton()->changed, this, "_gradient_changed");
+	}
+
+	_gradient = gradient;
+
+	// Connect to the gradient so the line will update when the ColorRamp is changed
+	if(_gradient.is_valid()) {
+		(**_gradient).connect(CoreStringNames::get_singleton()->changed, this, "_gradient_changed");
+	}
+
+	update();
+}
+
+Ref<ColorRamp> Line2D::get_gradient() const {
+	return _gradient;
+}
+
+void Line2D::set_texture(const Ref<Texture>& texture) {
+	_texture = texture;
+	update();
+}
+
+Ref<Texture> Line2D::get_texture() const {
+	return _texture;
+}
+
+void Line2D::set_texture_mode(const LineTextureMode mode) {
+	_texture_mode = mode;
+	update();
+}
+
+LineTextureMode Line2D::get_texture_mode() const {
+	return _texture_mode;
+}
+
+void Line2D::set_joint_mode(LineJointMode mode) {
+	_joint_mode = mode;
+	update();
+}
+
+LineJointMode Line2D::get_joint_mode() const {
+	return _joint_mode;
+}
+
+void Line2D::set_begin_cap_mode(LineCapMode mode) {
+	_begin_cap_mode = mode;
+	update();
+}
+
+LineCapMode Line2D::get_begin_cap_mode() const {
+	return _begin_cap_mode;
+}
+
+void Line2D::set_end_cap_mode(LineCapMode mode) {
+	_end_cap_mode = mode;
+	update();
+}
+
+LineCapMode Line2D::get_end_cap_mode() const {
+	return _end_cap_mode;
+}
+
+void Line2D::_notification(int p_what) {
+	switch(p_what) {
+	case NOTIFICATION_DRAW:
+		_draw();
+		break;
+	}
+}
+
+void Line2D::set_sharp_limit(float limit) {
+	if(limit < 0.f)
+		limit = 0.f;
+	_sharp_limit = limit;
+	update();
+}
+
+float Line2D::get_sharp_limit() const {
+	return _sharp_limit;
+}
+
+void Line2D::set_round_precision(int precision) {
+	if(precision < 1)
+		precision = 1;
+	_round_precision = precision;
+	update();
+}
+
+int Line2D::get_round_precision() const {
+	return _round_precision;
+}
+
+void Line2D::_draw() {
+	if(_points.size() <= 1 || _width == 0.f)
+		return;
+
+	// TODO Is this really needed?
+	// Copy points for faster access
+	Vector<Vector2> points;
+	points.resize(_points.size());
+	int len = points.size(); {
+		PoolVector<Vector2>::Read points_read = _points.read();
+		for(int i = 0; i < len; ++i) {
+			points[i] = points_read[i];
+		}
+	}
+
+	// TODO Maybe have it as member rather than copying parameters and allocating memory?
+	LineBuilder lb;
+	lb.points = points;
+	lb.default_color = _default_color;
+	lb.gradient = *_gradient;
+	lb.texture_mode = _texture_mode;
+	lb.joint_mode = _joint_mode;
+	lb.begin_cap_mode = _begin_cap_mode;
+	lb.end_cap_mode = _end_cap_mode;
+	lb.round_precision = _round_precision;
+	lb.sharp_limit = _sharp_limit;
+	lb.width = _width;
+
+	lb.build();
+
+	RID texture_rid;
+	if(_texture.is_valid())
+		texture_rid = (**_texture).get_rid();
+
+	VS::get_singleton()->canvas_item_add_triangle_array(
+				get_canvas_item(),
+				lb.indices,
+				lb.vertices,
+				lb.colors,
+				lb.uvs,
+				texture_rid);
+
+	// DEBUG
+	// Draw wireframe
+//	if(lb.indices.size() % 3 == 0) {
+//		Color col(0,0,0);
+//		for(int i = 0; i < lb.indices.size(); i += 3) {
+//			int vi = lb.indices[i];
+//			int lbvsize = lb.vertices.size();
+//			Vector2 a = lb.vertices[lb.indices[i]];
+//			Vector2 b = lb.vertices[lb.indices[i+1]];
+//			Vector2 c = lb.vertices[lb.indices[i+2]];
+//			draw_line(a, b, col);
+//			draw_line(b, c, col);
+//			draw_line(c, a, col);
+//		}
+//		for(int i = 0; i < lb.vertices.size(); ++i) {
+//			Vector2 p = lb.vertices[i];
+//			draw_rect(Rect2(p.x-1, p.y-1, 2, 2), Color(0,0,0,0.5));
+//		}
+//	}
+}
+
+void Line2D::_gradient_changed() {
+	update();
+}
+
+// static
+void Line2D::_bind_methods() {
+
+	ClassDB::bind_method(_MD("set_points","points"), &Line2D::set_points);
+	ClassDB::bind_method(_MD("get_points"), &Line2D::get_points);
+
+	ClassDB::bind_method(_MD("set_point_pos","i", "pos"), &Line2D::set_point_pos);
+	ClassDB::bind_method(_MD("get_point_pos", "i"), &Line2D::get_point_pos);
+
+	ClassDB::bind_method(_MD("get_point_count"), &Line2D::get_point_count);
+
+	ClassDB::bind_method(_MD("add_point", "pos"), &Line2D::add_point);
+	ClassDB::bind_method(_MD("remove_point", "i"), &Line2D::remove_point);
+
+	ClassDB::bind_method(_MD("set_width","width"), &Line2D::set_width);
+	ClassDB::bind_method(_MD("get_width"), &Line2D::get_width);
+
+	ClassDB::bind_method(_MD("set_default_color", "color"), &Line2D::set_default_color);
+	ClassDB::bind_method(_MD("get_default_color"), &Line2D::get_default_color);
+
+	ClassDB::bind_method(_MD("set_gradient", "color"), &Line2D::set_gradient);
+	ClassDB::bind_method(_MD("get_gradient"), &Line2D::get_gradient);
+
+	ClassDB::bind_method(_MD("set_texture", "texture"), &Line2D::set_texture);
+	ClassDB::bind_method(_MD("get_texture"), &Line2D::get_texture);
+
+	ClassDB::bind_method(_MD("set_texture_mode", "mode"), &Line2D::set_texture_mode);
+	ClassDB::bind_method(_MD("get_texture_mode"), &Line2D::get_texture_mode);
+
+	ClassDB::bind_method(_MD("set_joint_mode", "mode"), &Line2D::set_joint_mode);
+	ClassDB::bind_method(_MD("get_joint_mode"), &Line2D::get_joint_mode);
+
+	ClassDB::bind_method(_MD("set_begin_cap_mode", "mode"), &Line2D::set_begin_cap_mode);
+	ClassDB::bind_method(_MD("get_begin_cap_mode"), &Line2D::get_begin_cap_mode);
+
+	ClassDB::bind_method(_MD("set_end_cap_mode", "mode"), &Line2D::set_end_cap_mode);
+	ClassDB::bind_method(_MD("get_end_cap_mode"), &Line2D::get_end_cap_mode);
+
+	ClassDB::bind_method(_MD("set_sharp_limit", "limit"), &Line2D::set_sharp_limit);
+	ClassDB::bind_method(_MD("get_sharp_limit"), &Line2D::get_sharp_limit);
+
+	ClassDB::bind_method(_MD("set_round_precision", "precision"), &Line2D::set_round_precision);
+	ClassDB::bind_method(_MD("get_round_precision"), &Line2D::get_round_precision);
+
+	ADD_PROPERTY(PropertyInfo(Variant::POOL_VECTOR2_ARRAY, "points"), _SCS("set_points"), _SCS("get_points"));
+	ADD_PROPERTY(PropertyInfo(Variant::REAL, "width"), _SCS("set_width"), _SCS("get_width"));
+	ADD_PROPERTY(PropertyInfo(Variant::COLOR, "default_color"), _SCS("set_default_color"), _SCS("get_default_color"));
+	ADD_PROPERTYNZ( PropertyInfo( Variant::OBJECT, "gradient", PROPERTY_HINT_RESOURCE_TYPE, "ColorRamp"), _SCS("set_gradient"), _SCS("get_gradient" ) );
+	ADD_PROPERTYNZ( PropertyInfo( Variant::OBJECT, "texture", PROPERTY_HINT_RESOURCE_TYPE, "Texture"), _SCS("set_texture"), _SCS("get_texture" ) );
+	ADD_PROPERTYNZ( PropertyInfo( Variant::INT, "texture_mode", PROPERTY_HINT_ENUM, "None,Tile" ), _SCS("set_texture_mode"),_SCS("get_texture_mode" ) );
+	ADD_PROPERTYNZ( PropertyInfo( Variant::INT, "joint_mode", PROPERTY_HINT_ENUM, "Sharp,Bevel,Round" ), _SCS("set_joint_mode"),_SCS("get_joint_mode" ) );
+	ADD_PROPERTYNZ( PropertyInfo( Variant::INT, "begin_cap_mode", PROPERTY_HINT_ENUM, "None,Box,Round" ), _SCS("set_begin_cap_mode"),_SCS("get_begin_cap_mode" ) );
+	ADD_PROPERTYNZ( PropertyInfo( Variant::INT, "end_cap_mode", PROPERTY_HINT_ENUM, "None,Box,Round" ), _SCS("set_end_cap_mode"),_SCS("get_end_cap_mode" ) );
+	ADD_PROPERTY(PropertyInfo(Variant::REAL, "sharp_limit"), _SCS("set_sharp_limit"), _SCS("get_sharp_limit"));
+	ADD_PROPERTY(PropertyInfo(Variant::INT, "round_precision"), _SCS("set_round_precision"), _SCS("get_round_precision"));
+
+	BIND_CONSTANT(LINE_JOINT_SHARP);
+	BIND_CONSTANT(LINE_JOINT_BEVEL);
+	BIND_CONSTANT(LINE_JOINT_ROUND);
+
+	BIND_CONSTANT(LINE_CAP_NONE);
+	BIND_CONSTANT(LINE_CAP_BOX);
+	BIND_CONSTANT(LINE_CAP_ROUND);
+
+	BIND_CONSTANT(LINE_TEXTURE_NONE);
+	BIND_CONSTANT(LINE_TEXTURE_TILE);
+
+	ClassDB::bind_method(_MD("_gradient_changed"), &Line2D::_gradient_changed);
+
+}
+
+
diff --git a/scene/2d/line_2d.h b/scene/2d/line_2d.h
new file mode 100644
index 0000000000..f4e2eb7a55
--- /dev/null
+++ b/scene/2d/line_2d.h
@@ -0,0 +1,80 @@
+#ifndef LINE2D_H
+#define LINE2D_H
+
+#include "node_2d.h"
+#include "line_builder.h"
+
+
+class Line2D : public Node2D {
+
+	GDCLASS(Line2D, Node2D)
+
+public:
+	Line2D();
+
+	void set_points(const PoolVector<Vector2> & p_points);
+	PoolVector<Vector2> get_points() const;
+
+	void set_point_pos(int i, Vector2 pos);
+	Vector2 get_point_pos(int i) const;
+
+	int get_point_count() const;
+
+	void add_point(Vector2 pos);
+	void remove_point(int i);
+
+	void set_width(float width);
+	float get_width() const;
+
+	void set_default_color(Color color);
+	Color get_default_color() const;
+
+	void set_gradient(const Ref<ColorRamp>& gradient);
+	Ref<ColorRamp> get_gradient() const;
+
+	void set_texture(const Ref<Texture>& texture);
+	Ref<Texture> get_texture() const;
+
+	void set_texture_mode(const LineTextureMode mode);
+	LineTextureMode get_texture_mode() const;
+
+	void set_joint_mode(LineJointMode mode);
+	LineJointMode get_joint_mode() const;
+
+	void set_begin_cap_mode(LineCapMode mode);
+	LineCapMode get_begin_cap_mode() const;
+
+	void set_end_cap_mode(LineCapMode mode);
+	LineCapMode get_end_cap_mode() const;
+
+	void set_sharp_limit(float limit);
+	float get_sharp_limit() const;
+
+	void set_round_precision(int precision);
+	int get_round_precision() const;
+
+protected:
+	void _notification(int p_what);
+	void _draw();
+
+	static void _bind_methods();
+
+private:
+	void _gradient_changed();
+
+private:
+	PoolVector<Vector2> _points;
+	LineJointMode _joint_mode;
+	LineCapMode _begin_cap_mode;
+	LineCapMode _end_cap_mode;
+	float _width;
+	Color _default_color;
+	Ref<ColorRamp> _gradient;
+	Ref<Texture> _texture;
+	LineTextureMode _texture_mode;
+	float _sharp_limit;
+	int _round_precision;
+
+};
+
+#endif // LINE2D_H
diff --git a/scene/2d/line_builder.cpp b/scene/2d/line_builder.cpp
new file mode 100644
index 0000000000..230f72cccd
--- /dev/null
+++ b/scene/2d/line_builder.cpp
@@ -0,0 +1,563 @@
+#include "line_builder.h"
+
+//----------------------------------------------------------------------------
+// Util
+//----------------------------------------------------------------------------
+
+enum SegmentIntersectionResult {
+	SEGMENT_PARALLEL = 0,
+	SEGMENT_NO_INTERSECT = 1,
+	SEGMENT_INTERSECT = 2
+};
+
+static SegmentIntersectionResult segment_intersection(
+		Vector2 a, Vector2 b, Vector2 c, Vector2 d,
+		Vector2 * out_intersection)
+{
+	// http://paulbourke.net/geometry/pointlineplane/ <-- Good stuff
+	Vector2 cd = d - c;
+	Vector2 ab = b - a;
+	float div = cd.y*ab.x - cd.x*ab.y;
+
+	if(Math::abs(div) > 0.001f) {
+		float ua = (cd.x * (a.y-c.y) - cd.y * (a.x-c.x)) / div;
+		float ub = (ab.x * (a.y-c.y) - ab.y * (a.x-c.x)) / div;
+		*out_intersection = a + ua * ab;
+		if(ua >= 0.f && ua <= 1.f &&
+		   ub >= 0.f && ub <= 1.f)
+			return SEGMENT_INTERSECT;
+		return SEGMENT_NO_INTERSECT;
+	}
+
+	return SEGMENT_PARALLEL;
+}
+
+// TODO I'm pretty sure there is an even faster way to swap things
+template <typename T>
+static inline void swap(T & a, T & b) {
+	T tmp = a;
+	a = b;
+	b = tmp;
+}
+
+static float calculate_total_distance(const Vector<Vector2> & points) {
+	float d = 0.f;
+	for(int i = 1; i < points.size(); ++i) {
+		d += points[i].distance_to(points[i-1]);
+	}
+	return d;
+}
+
+static inline Vector2 rotate90(const Vector2 & v) {
+	// Note: the 2D referential is X-right, Y-down
+	return Vector2(v.y, -v.x);
+}
+
+static inline Vector2 interpolate(const Rect2 & r, const Vector2 & v) {
+	return Vector2(
+		Math::lerp(r.get_pos().x, r.get_pos().x + r.get_size().x, v.x),
+		Math::lerp(r.get_pos().y, r.get_pos().y + r.get_size().y, v.y)
+	);
+}
+
+//----------------------------------------------------------------------------
+// LineBuilder
+//----------------------------------------------------------------------------
+
+LineBuilder::LineBuilder() {
+	joint_mode = LINE_JOINT_SHARP;
+	width = 10;
+	default_color = Color(0.4,0.5,1);
+	gradient = NULL;
+	sharp_limit = 2.f;
+	round_precision = 8;
+	begin_cap_mode = LINE_CAP_NONE;
+	end_cap_mode = LINE_CAP_NONE;
+
+	_interpolate_color = false;
+	_last_index[0] = 0;
+	_last_index[1] = 0;
+}
+
+
+void LineBuilder::clear_output() {
+	vertices.clear();
+	colors.clear();
+	indices.clear();
+}
+
+void LineBuilder::build() {
+
+	// Need at least 2 points to draw a line
+	if(points.size() < 2) {
+		clear_output();
+		return;
+	}
+
+	const float hw = width / 2.f;
+	const float hw_sq = hw*hw;
+	const float sharp_limit_sq = sharp_limit * sharp_limit;
+	const int len = points.size();
+
+	// Initial values
+
+	Vector2 pos0 = points[0];
+	Vector2 pos1 = points[1];
+	Vector2 f0 = (pos1 - pos0).normalized();
+	Vector2 u0 = rotate90(f0);
+	Vector2 pos_up0 = pos0 + u0 * hw;
+	Vector2 pos_down0 = pos0 - u0 * hw;
+
+	Color color0;
+	Color color1;
+
+	float current_distance0 = 0.f;
+	float current_distance1 = 0.f;
+	float total_distance;
+	_interpolate_color = gradient != NULL;
+	bool distance_required = _interpolate_color || texture_mode == LINE_TEXTURE_TILE;
+	if(distance_required)
+		total_distance = calculate_total_distance(points);
+	if(_interpolate_color)
+		color0 = gradient->get_color(0);
+	else
+		colors.push_back(default_color);
+
+	float uvx0 = 0.f;
+	float uvx1 = 0.f;
+
+	// Begin cap
+	if(begin_cap_mode == LINE_CAP_BOX) {
+		// Push back first vertices a little bit
+		pos_up0 -= f0 * hw;
+		pos_down0 -= f0 * hw;
+		// The line's outer length will be a little higher due to begin and end caps
+		total_distance += width;
+		current_distance0 += hw;
+		current_distance1 = current_distance0;
+	}
+	else if(begin_cap_mode == LINE_CAP_ROUND) {
+		if(texture_mode == LINE_TEXTURE_TILE) {
+			uvx0 = 0.5f;
+		}
+		new_arc(pos0, pos_up0 - pos0, -Math_PI, color0, Rect2(0.f, 0.f, 1.f, 1.f));
+		total_distance += width;
+		current_distance0 += hw;
+		current_distance1 = current_distance0;
+	}
+
+	strip_begin(pos_up0, pos_down0, color0, uvx0);
+
+	//  pos_up0 ------------- pos_up1 --------------------
+	//     |                     |
+	//   pos0 - - - - - - - - - pos1 - - - - - - - - - pos2
+	//     |                     |
+	// pos_down0 ------------ pos_down1 ------------------
+	//
+	//   i-1                     i                      i+1
+
+	// http://labs.hyperandroid.com/tag/opengl-lines
+	// (not the same implementation but visuals help a lot)
+
+	// For each additional segment
+	for(int i = 1; i < len-1; ++i) {
+
+		pos1 = points[i];
+		Vector2 pos2 = points[i+1];
+
+		Vector2 f1 = (pos2 - pos1).normalized();
+		Vector2 u1 = rotate90(f1);
+
+		// Determine joint orientation
+		const float dp = u0.dot(f1);
+		const Orientation orientation = (dp > 0.f ? UP : DOWN);
+
+		Vector2 inner_normal0, inner_normal1;
+		if(orientation == UP) {
+			inner_normal0 = u0 * hw;
+			inner_normal1 = u1 * hw;
+		}
+		else {
+			inner_normal0 = -u0 * hw;
+			inner_normal1 = -u1 * hw;
+		}
+
+		// ---------------------------
+		//                        /
+		// 0                     /    1
+		//                      /          /
+		// --------------------x------    /
+		//                    /          /    (here shown with orientation == DOWN)
+		//                   /          /
+		//                  /          /
+		//                 /          /
+		//                     2     /
+		//                          /
+
+		// Find inner intersection at the joint
+		Vector2 corner_pos_in, corner_pos_out;
+		SegmentIntersectionResult intersection_result = segment_intersection(
+					pos0 + inner_normal0, pos1 + inner_normal0,
+					pos1 + inner_normal1, pos2 + inner_normal1,
+					&corner_pos_in);
+
+		if(intersection_result == SEGMENT_INTERSECT)
+			// Inner parts of the segments intersect
+			corner_pos_out = 2.f * pos1 - corner_pos_in;
+		else {
+			// No intersection, segments are either parallel or too sharp
+			corner_pos_in = pos1 + inner_normal0;
+			corner_pos_out = pos1 - inner_normal0;
+		}
+
+		Vector2 corner_pos_up, corner_pos_down;
+		if(orientation == UP) {
+			corner_pos_up = corner_pos_in;
+			corner_pos_down = corner_pos_out;
+		}
+		else {
+			corner_pos_up = corner_pos_out;
+			corner_pos_down = corner_pos_in;
+		}
+
+		LineJointMode current_joint_mode = joint_mode;
+
+		Vector2 pos_up1, pos_down1;
+		if(intersection_result == SEGMENT_INTERSECT) {
+			// Fallback on bevel if sharp angle is too high (because it would produce very long miters)
+			if(current_joint_mode == LINE_JOINT_SHARP && corner_pos_out.distance_squared_to(pos1) / hw_sq > sharp_limit_sq) {
+				current_joint_mode = LINE_JOINT_BEVEL;
+			}
+			if(current_joint_mode == LINE_JOINT_SHARP) {
+				// In this case, we won't create joint geometry,
+				// The previous and next line quads will directly share an edge.
+				pos_up1 = corner_pos_up;
+				pos_down1 = corner_pos_down;
+			}
+			else {
+				// Bevel or round
+				if(orientation == UP) {
+					pos_up1 = corner_pos_up;
+					pos_down1 = pos1 - u0 * hw;
+				}
+				else {
+					pos_up1 = pos1 + u0 * hw;
+					pos_down1 = corner_pos_down;
+				}
+			}
+		}
+		else {
+			// No intersection: fallback
+			pos_up1 = corner_pos_up;
+			pos_down1 = corner_pos_down;
+		}
+
+		// Add current line body quad
+		// Triangles are clockwise
+		if(distance_required) {
+			current_distance1 += pos0.distance_to(pos1);
+		}
+		if(_interpolate_color) {
+			color1 = gradient->get_color_at_offset(current_distance1 / total_distance);
+		}
+		if(texture_mode == LINE_TEXTURE_TILE) {
+			uvx0 = current_distance0 / width;
+			uvx1 = current_distance1 / width;
+		}
+
+		strip_add_quad(pos_up1, pos_down1, color1, uvx1);
+
+		// Swap vars for use in the next line
+		color0 = color1;
+		u0 = u1;
+		f0 = f1;
+		pos0 = pos1;
+		current_distance0 = current_distance1;
+		if(intersection_result == SEGMENT_INTERSECT) {
+			if(current_joint_mode == LINE_JOINT_SHARP) {
+				pos_up0 = pos_up1;
+				pos_down0 = pos_down1;
+			}
+			else {
+				if(orientation == UP) {
+					pos_up0 = corner_pos_up;
+					pos_down0 = pos1 - u1 * hw;
+				}
+				else {
+					pos_up0 = pos1 + u1 * hw;
+					pos_down0 = corner_pos_down;
+				}
+			}
+		}
+		else {
+			pos_up0 = pos1 + u1 * hw;
+			pos_down0 = pos1 - u1 * hw;
+		}
+		// From this point, bu0 and bd0 concern the next segment
+
+		// Add joint geometry
+		if(current_joint_mode != LINE_JOINT_SHARP) {
+
+			// ________________ cbegin
+			//               / \
+			//              /   \
+			// ____________/_ _ _\ cend
+			//             |     |
+			//             |     |
+			//             |     |
+
+			Vector2 cbegin, cend;
+			if(orientation == UP) {
+				cbegin = pos_down1;
+				cend = pos_down0;
+			}
+			else {
+				cbegin = pos_up1;
+				cend = pos_up0;
+			}
+
+			if(current_joint_mode == LINE_JOINT_BEVEL) {
+				strip_add_tri(cend, orientation);
+			}
+			else if(current_joint_mode == LINE_JOINT_ROUND) {
+				Vector2 vbegin = cbegin - pos1;
+				Vector2 vend = cend - pos1;
+				strip_add_arc(pos1, vend.angle_to(vbegin), orientation);
+			}
+
+			if(intersection_result != SEGMENT_INTERSECT)
+				// In this case the joint is too fucked up to be re-used,
+				// start again the strip with fallback points
+				strip_begin(pos_up0, pos_down0, color1, uvx1);
+		}
+	}
+
+	// Last (or only) segment
+
+	pos1 = points[points.size()-1];
+
+	Vector2 pos_up1 = pos1 + u0 * hw;
+	Vector2 pos_down1 = pos1 - u0 * hw;
+
+	// End cap (box)
+	if(end_cap_mode == LINE_CAP_BOX) {
+		pos_up1 += f0 * hw;
+		pos_down1 += f0 * hw;
+	}
+
+	if(distance_required) {
+		current_distance1 += pos0.distance_to(pos1);
+	}
+	if(_interpolate_color) {
+		color1 = gradient->get_color(gradient->get_points_count()-1);
+	}
+	if(texture_mode == LINE_TEXTURE_TILE) {
+		uvx1 = current_distance1 / width;
+	}
+
+	strip_add_quad(pos_up1, pos_down1, color1, uvx1);
+
+	// End cap (round)
+	if(end_cap_mode == LINE_CAP_ROUND) {
+		// Note: color is not used in case we don't interpolate...
+		Color color = _interpolate_color ? gradient->get_color(gradient->get_points_count()-1) : Color(0,0,0);
+		new_arc(pos1, pos_up1 - pos1, Math_PI, color, Rect2(uvx1-0.5f, 0.f, 1.f, 1.f));
+	}
+}
+
+void LineBuilder::strip_begin(Vector2 up, Vector2 down, Color color, float uvx) {
+	int vi = vertices.size();
+
+	vertices.push_back(up);
+	vertices.push_back(down);
+
+	if(_interpolate_color) {
+		colors.push_back(color);
+		colors.push_back(color);
+	}
+
+	if(texture_mode != LINE_TEXTURE_NONE) {
+		uvs.push_back(Vector2(uvx, 0.f));
+		uvs.push_back(Vector2(uvx, 1.f));
+	}
+
+	_last_index[UP] = vi;
+	_last_index[DOWN] = vi+1;
+}
+
+void LineBuilder::strip_new_quad(Vector2 up, Vector2 down, Color color, float uvx) {
+	int vi = vertices.size();
+
+	vertices.push_back(vertices[_last_index[UP]]);
+	vertices.push_back(vertices[_last_index[DOWN]]);
+	vertices.push_back(up);
+	vertices.push_back(down);
+
+	if(_interpolate_color) {
+		colors.push_back(color);
+		colors.push_back(color);
+		colors.push_back(color);
+		colors.push_back(color);
+	}
+
+	if(texture_mode != LINE_TEXTURE_NONE) {
+		uvs.push_back(uvs[_last_index[UP]]);
+		uvs.push_back(uvs[_last_index[DOWN]]);
+		uvs.push_back(Vector2(uvx, UP));
+		uvs.push_back(Vector2(uvx, DOWN));
+	}
+
+	indices.push_back(vi);
+	indices.push_back(vi+3);
+	indices.push_back(vi+1);
+	indices.push_back(vi);
+	indices.push_back(vi+2);
+	indices.push_back(vi+3);
+
+	_last_index[UP] = vi+2;
+	_last_index[DOWN] = vi+3;
+}
+
+void LineBuilder::strip_add_quad(Vector2 up, Vector2 down, Color color, float uvx) {
+	int vi = vertices.size();
+
+	vertices.push_back(up);
+	vertices.push_back(down);
+
+	if(_interpolate_color) {
+		colors.push_back(color);
+		colors.push_back(color);
+	}
+
+	if(texture_mode != LINE_TEXTURE_NONE) {
+		uvs.push_back(Vector2(uvx, 0.f));
+		uvs.push_back(Vector2(uvx, 1.f));
+	}
+
+	indices.push_back(_last_index[UP]);
+	indices.push_back(vi+1);
+	indices.push_back(_last_index[DOWN]);
+	indices.push_back(_last_index[UP]);
+	indices.push_back(vi);
+	indices.push_back(vi+1);
+
+	_last_index[UP] = vi;
+	_last_index[DOWN] = vi+1;
+}
+
+void LineBuilder::strip_add_tri(Vector2 up, Orientation orientation) {
+	int vi = vertices.size();
+
+	vertices.push_back(up);
+
+	if(_interpolate_color) {
+		colors.push_back(colors[colors.size()-1]);
+	}
+
+	Orientation opposite_orientation = orientation == UP ? DOWN : UP;
+
+	if(texture_mode != LINE_TEXTURE_NONE) {
+		// UVs are just one slice of the texture all along
+		// (otherwise we can't share the bottom vertice)
+		uvs.push_back(uvs[_last_index[opposite_orientation]]);
+	}
+
+	indices.push_back(_last_index[opposite_orientation]);
+	indices.push_back(vi);
+	indices.push_back(_last_index[orientation]);
+
+	_last_index[opposite_orientation] = vi;
+}
+
+void LineBuilder::strip_add_arc(Vector2 center, float angle_delta, Orientation orientation) {
+
+	// Take the two last vertices and extrude an arc made of triangles
+	// that all share one of the initial vertices
+
+	Orientation opposite_orientation = orientation == UP ? DOWN : UP;
+	Vector2 vbegin = vertices[_last_index[opposite_orientation]] - center;
+	float radius = vbegin.length();
+	float angle_step = Math_PI / static_cast<float>(round_precision);
+	float steps = Math::abs(angle_delta) / angle_step;
+
+	if(angle_delta < 0.f)
+		angle_step = -angle_step;
+
+	float t = vbegin.angle_to(Vector2(1, 0));
+	float end_angle = t + angle_delta;
+	Vector2 rpos(0,0);
+
+	// Arc vertices
+	for(int ti = 0; ti < steps; ++ti, t += angle_step) {
+		rpos = center + Vector2(Math::cos(t), Math::sin(t)) * radius;
+		strip_add_tri(rpos, orientation);
+	}
+
+	// Last arc vertice
+	rpos = center + Vector2(Math::cos(end_angle), Math::sin(end_angle)) * radius;
+	strip_add_tri(rpos, orientation);
+}
+
+void LineBuilder::new_arc(Vector2 center, Vector2 vbegin, float angle_delta, Color color, Rect2 uv_rect) {
+
+	// Make a standalone arc that doesn't use existing vertices,
+	// with undistorted UVs from withing a square section
+
+	float radius = vbegin.length();
+	float angle_step = Math_PI / static_cast<float>(round_precision);
+	float steps = Math::abs(angle_delta) / angle_step;
+
+	if(angle_delta < 0.f)
+		angle_step = -angle_step;
+
+	float t = vbegin.angle_to(Vector2(1, 0));
+	float end_angle = t + angle_delta;
+	Vector2 rpos(0,0);
+	float tt_begin = -Math_PI / 2.f;
+	float tt = tt_begin;
+
+	// Center vertice
+	int vi = vertices.size();
+	vertices.push_back(center);
+	if(_interpolate_color)
+		colors.push_back(color);
+	if(texture_mode != LINE_TEXTURE_NONE)
+		uvs.push_back(interpolate(uv_rect, Vector2(0.5f, 0.5f)));
+
+	// Arc vertices
+	for(int ti = 0; ti < steps; ++ti, t += angle_step) {
+		Vector2 sc = Vector2(Math::cos(t), Math::sin(t));
+		rpos = center + sc * radius;
+
+		vertices.push_back(rpos);
+		if(_interpolate_color)
+			colors.push_back(color);
+		if(texture_mode != LINE_TEXTURE_NONE) {
+			Vector2 tsc = Vector2(Math::cos(tt), Math::sin(tt));
+			uvs.push_back(interpolate(uv_rect, 0.5f*(tsc+Vector2(1.f,1.f))));
+			tt += angle_step;
+		}
+	}
+
+	// Last arc vertice
+	Vector2 sc = Vector2(Math::cos(end_angle), Math::sin(end_angle));
+	rpos = center + sc * radius;
+	vertices.push_back(rpos);
+	if(_interpolate_color)
+		colors.push_back(color);
+	if(texture_mode != LINE_TEXTURE_NONE) {
+		tt = tt_begin + angle_delta;
+		Vector2 tsc = Vector2(Math::cos(tt), Math::sin(tt));
+		uvs.push_back(interpolate(uv_rect, 0.5f*(tsc+Vector2(1.f,1.f))));
+	}
+
+	// Make up triangles
+	int vi0 = vi;
+	for(int ti = 0; ti < steps; ++ti) {
+		indices.push_back(vi0);
+		indices.push_back(++vi);
+		indices.push_back(vi+1);
+	}
+}
+
+
diff --git a/scene/2d/line_builder.h b/scene/2d/line_builder.h
new file mode 100644
index 0000000000..73419f88d8
--- /dev/null
+++ b/scene/2d/line_builder.h
@@ -0,0 +1,76 @@
+#ifndef LINE_BUILDER_H
+#define LINE_BUILDER_H
+
+#include "math_2d.h"
+#include "color.h"
+#include "scene/resources/color_ramp.h"
+
+enum LineJointMode {
+	LINE_JOINT_SHARP = 0,
+	LINE_JOINT_BEVEL,
+	LINE_JOINT_ROUND
+};
+
+enum LineCapMode {
+	LINE_CAP_NONE = 0,
+	LINE_CAP_BOX,
+	LINE_CAP_ROUND
+};
+
+enum LineTextureMode {
+	LINE_TEXTURE_NONE = 0,
+	LINE_TEXTURE_TILE
+	// TODO STRETCH mode
+};
+
+class LineBuilder {
+public:
+	// TODO Move in a struct and reference it
+	// Input
+	Vector<Vector2> points;
+	LineJointMode joint_mode;
+	LineCapMode begin_cap_mode;
+	LineCapMode end_cap_mode;
+	float width;
+	Color default_color;
+	ColorRamp* gradient;
+	LineTextureMode texture_mode;
+	float sharp_limit;
+	int round_precision;
+	// TODO offset_joints option (offers alternative implementation of round joints)
+
+	// TODO Move in a struct and reference it
+	// Output
+	Vector<Vector2> vertices;
+	Vector<Color> colors;
+	Vector<Vector2> uvs;
+	Vector<int> indices;
+
+	LineBuilder();
+
+	void build();
+	void clear_output();
+
+private:
+	enum Orientation {
+		UP = 0,
+		DOWN = 1
+	};
+
+	// Triangle-strip methods
+	void strip_begin(Vector2 up, Vector2 down, Color color, float uvx);
+	void strip_new_quad(Vector2 up, Vector2 down, Color color, float uvx);
+	void strip_add_quad(Vector2 up, Vector2 down, Color color, float uvx);
+	void strip_add_tri(Vector2 up, Orientation orientation);
+	void strip_add_arc(Vector2 center, float angle_delta, Orientation orientation);
+
+	void new_arc(Vector2 center, Vector2 vbegin, float angle_delta, Color color, Rect2 uv_rect);
+
+private:
+	bool _interpolate_color;
+	int _last_index[2]; // Index of last up and down vertices of the strip
+
+};
+
+
+#endif // LINE_BUILDER_H