Add the "Along Normals" parameter to the 'Jitter Points' node (#3983)

* Add the "Along Normals" parameter to the 'Jitter Points' node

* Fix the edge case of a self-loops

Author: Keavon

editor/src/messages/portfolio/document_migration.rs

@@ -1860,6 +1860,19 @@ fn migrate_node(node_id: &NodeId, node: &DocumentNode, network_path: &[NodeId],
 			.set_input(&InputConnector::node(*node_id, 1), NodeInput::value(TaggedValue::ScaleType(ScaleType::Magnitude), false), network_path);
 	}
 
+	// Add the "Along Normals" parameter to the "Jitter Points" node
+	if reference == DefinitionIdentifier::ProtoNode(graphene_std::vector::jitter_points::IDENTIFIER) && inputs_count == 3 {
+		let mut node_template = resolve_document_node_type(&reference)?.default_node_template();
+		let old_inputs = document.network_interface.replace_inputs(node_id, network_path, &mut node_template)?;
+
+		document.network_interface.set_input(&InputConnector::node(*node_id, 0), old_inputs[0].clone(), network_path);
+		document.network_interface.set_input(&InputConnector::node(*node_id, 1), old_inputs[1].clone(), network_path);
+		document.network_interface.set_input(&InputConnector::node(*node_id, 2), old_inputs[2].clone(), network_path);
+		document
+			.network_interface
+			.set_input(&InputConnector::node(*node_id, 3), NodeInput::value(TaggedValue::Bool(false), false), network_path);
+	}
+
 	// ==================================
 	// PUT ALL MIGRATIONS ABOVE THIS LINE
 	// ==================================

node-graph/libraries/vector-types/src/vector/vector_attributes.rs

@@ -436,6 +436,93 @@ impl SegmentDomain {
 		self.all_connected(point).next().is_some()
 	}
 
+	/// Computes the direction-of-travel tangent at one endpoint of a segment.
+	/// Uses the "first distinct control point" pattern: iterates through the Bezier control points
+	/// from the anchor outward, returning the direction to the first one that differs in position.
+	/// This handles zero-length handles by finding the tangent direction in the limit.
+	/// Returns `DVec2::ZERO` if all control points coincide (fully degenerate segment).
+	fn segment_tangent_at_endpoint(&self, segment_index: usize, positions: &[DVec2], at_start: bool) -> DVec2 {
+		let anchor_start = positions[self.start_point[segment_index]];
+		let anchor_end = positions[self.end_point[segment_index]];
+
+		// Build ordered control points for this segment
+		let (points, count) = match self.handles[segment_index] {
+			BezierHandles::Linear => ([anchor_start, anchor_end, DVec2::ZERO, DVec2::ZERO], 2),
+			BezierHandles::Quadratic { handle } => ([anchor_start, handle, anchor_end, DVec2::ZERO], 3),
+			BezierHandles::Cubic { handle_start, handle_end } => ([anchor_start, handle_start, handle_end, anchor_end], 4),
+		};
+
+		let not_near = |a: DVec2, b: DVec2| a.distance_squared(b) > f64::EPSILON * 1e3;
+
+		if at_start {
+			let anchor = points[0];
+			points[1..count].iter().find(|&&p| not_near(p, anchor)).map_or(DVec2::ZERO, |&point| point - anchor)
+		} else {
+			let anchor = points[count - 1];
+			points[..count - 1].iter().rev().find(|&&p| not_near(p, anchor)).map_or(DVec2::ZERO, |&point| anchor - point)
+		}
+	}
+
+	/// Computes the average tangent direction at a point based on its 1 or 2 connected segments.
+	/// Returns `None` for points with 0 or 3+ connections (ambiguous or undefined tangent),
+	/// or if the tangent is degenerate (all control points coincide).
+	pub fn point_tangent(&self, point_index: usize, positions: &[DVec2]) -> Option<DVec2> {
+		// Collect connected segments with their relationship to this point (at_start flag)
+		let mut connections: [(usize, bool); 2] = [(0, false); 2];
+		let mut connection_count = 0;
+
+		for (segment_index, (&start, &end)) in self.start_point.iter().zip(&self.end_point).enumerate() {
+			// Self-loop segments count as two connections (outgoing and incoming)
+			let is_start = start == point_index;
+			let is_end = end == point_index;
+
+			if !is_start && !is_end {
+				continue;
+			}
+
+			if is_start {
+				if connection_count >= 2 {
+					return None;
+				}
+				connections[connection_count] = (segment_index, true);
+				connection_count += 1;
+			}
+			if is_end {
+				if connection_count >= 2 {
+					return None;
+				}
+				connections[connection_count] = (segment_index, false);
+				connection_count += 1;
+			}
+		}
+
+		if connection_count == 0 {
+			return None;
+		}
+
+		// Compute the direction-of-travel tangent for the first connection
+		let (segment_index, at_start) = connections[0];
+		let tangent1 = self.segment_tangent_at_endpoint(segment_index, positions, at_start).try_normalize();
+
+		if connection_count == 1 {
+			return tangent1;
+		}
+
+		// Compute the direction-of-travel tangent for the second connection
+		let (segment_index, at_start) = connections[1];
+		let tangent2 = self.segment_tangent_at_endpoint(segment_index, positions, at_start).try_normalize();
+
+		// Average the two normalized tangents
+		let average = tangent1? + tangent2?;
+
+		// If the tangents are nearly opposite (straight-through), use t1 directly
+		if average.length_squared() < (f64::EPSILON * 1e3).powi(2) {
+			return tangent1;
+		}
+
+		average.try_normalize()
+	}
+
 	/// Iterates over segments in the domain.
 	///
 	/// Tuple is: (id, start point, end point, handles)

node-graph/nodes/vector/src/vector_nodes.rs

@@ -1879,14 +1879,21 @@ async fn spline(_: impl Ctx, content: Table<Vector>) -> Table<Vector> {
 		.collect()
 }
 
+/// Perturbs the positions of anchor points in vector geometry by random amounts and directions.
 #[node_macro::node(category("Vector: Modifier"), path(core_types::vector))]
 async fn jitter_points(
 	_: impl Ctx,
+	/// The vector geometry with points to be jittered.
 	content: Table<Vector>,
-	#[unit(" px")]
+	/// The maximum extent of the random distance each point can be offset.
 	#[default(5.)]
+	#[unit(" px")]
 	amount: f64,
+	/// Seed used to determine unique variations on all randomized offsets.
 	seed: SeedValue,
+	/// Whether to offset anchor points along their normal direction (perpendicular to the path) or in a random direction. Free-floating and branching points have no normal direction, so they receive a random-angled offset regardless of this setting.
+	#[default(true)]
+	along_normals: bool,
 ) -> Table<Vector> {
 	content
 		.into_iter()
@@ -1897,10 +1904,20 @@ async fn jitter_points(
 			let inverse_transform = if transform.matrix2.determinant() != 0. { transform.inverse() } else { Default::default() };
 
 			let deltas = (0..row.element.point_domain.positions().len())
-				.map(|_| {
-					let angle = rng.random::<f64>() * TAU;
-
-					inverse_transform.transform_vector2(DVec2::from_angle(angle) * rng.random::<f64>() * amount)
+				.map(|point_index| {
+					let normal = if along_normals {
+						row.element.segment_domain.point_tangent(point_index, row.element.point_domain.positions()).map(|t| t.perp())
+					} else {
+						None
+					};
+
+					let offset = if let Some(normal) = normal {
+						(rng.random::<f64>() * 2. - 1.) * normal
+					} else {
+						rng.random::<f64>() * DVec2::from_angle(rng.random::<f64>() * TAU)
+					};
+
+					inverse_transform.transform_vector2(offset * amount)
 				})
 				.collect::<Vec<_>>();
 			let mut already_applied = vec![false; row.element.point_domain.positions().len()];