Connector Routing: Orthogonal, Curved, and Straight Lines

People obsess over shapes and neglect the lines, but connectors are where diagrams most often fall apart. A set of tidy boxes joined by tangled, crossing, awkwardly routed lines reads as chaos, no matter how good the boxes look. Connector routing - how a line travels from one shape to another - is a real design decision with three main styles: orthogonal lines that turn at right angles, curved lines that bend smoothly, and straight lines that go point to point. Each communicates a slightly different feel and suits different diagrams.

This guide explains the three routing styles, when each is the right call, and the concrete techniques for reducing line crossings so a busy diagram stays legible. The reference tool is Atlas Diagram Studio at /diagrams, which supports all three routing styles, snapping and connection points, 1000-plus shapes, Mermaid and .drawio import, and export to PNG, SVG, PDF, PPTX, JSON, Mermaid, and .drawio. Getting routing right is one of the highest-leverage editing skills there is, because it works on every diagram you will ever draw.

The three routing styles

Orthogonal routing draws connectors as horizontal and vertical segments joined by right-angle turns, like a subway map or a circuit board. It is the default for most technical diagrams - flowcharts, architecture, network diagrams - because right angles align to a grid, making parallel lines tidy and structure easy to follow. Curved routing draws smooth bends instead of hard corners, giving a softer, more organic look that suits mind maps, relationship diagrams, and anything where a friendly feel matters more than grid precision. Straight routing connects two points with a single direct line, which is cleanest when shapes are laid out so direct lines do not cross much, as in simple graphs or entity-relationship sketches.

The choice is partly aesthetic and partly functional. Orthogonal excels when many lines run in parallel, because aligned right angles read as order; it struggles when it forces long detours around obstacles. Curved handles dense, many-to-many connection patterns more gracefully because gentle bends can pass each other without the harsh visual collision of crossing straight lines. Straight is the most honest about distance and direction but becomes a mess the moment layout forces lines to cross. Match the style to both the diagram type and the density of connections, not just to taste.

Choosing a routing style

A few reliable rules map diagram types to routing styles, though you should always let the actual density of your connections have the final say.

• Flowcharts and process diagrams: orthogonal, so the flow reads as a clean grid of right-angle turns.
• Software and network architecture: orthogonal, since parallel aligned lines communicate structured connections.
• Mind maps and brainstorms: curved, for an organic feel that radiates from a center.
• Relationship and concept maps: curved, because smooth bends handle many crossing links more gracefully than hard corners.
• Simple graphs with few connections: straight, which is the most direct and honest when lines rarely cross.
• Entity-relationship diagrams: straight or orthogonal depending on layout, with orthogonal winning as the schema grows.
• Mixed diagrams: pick one dominant style for consistency rather than mixing styles arbitrarily within one diagram.

Reducing line crossings

Crossings are the single biggest readability killer, because every crossing forces the reader to trace which line goes where. The most powerful fix is not a routing setting but layout: rearranging shapes so connections naturally flow without crossing does more than any clever routing can. Order nodes so connected shapes sit near each other, place hubs centrally, and orient the diagram so the dominant flow runs one direction - top to bottom or left to right - which alone eliminates many crossings. When a crossing is unavoidable, a small line jump or gap where one line hops another signals which is which.

Auto-layout is a strong ally here: the layered and hierarchical algorithms are built to minimize crossings by assigning shapes to ranks and ordering them to reduce tangles, and running one can instantly untangle a diagram you arranged by hand. After auto-layout, fine-tune manually. Other concrete moves: route related connections in parallel bundles rather than letting them wander, adjust where a line attaches to a shape so it exits toward its destination, and add waypoints to steer a connector around an obstacle instead of through a cluster. The guide on auto-layout algorithms at /guides/auto-layout-algorithms-guide goes deeper on how those crossing-minimizing algorithms work.

Connection points and clean attachment

Where a connector attaches to a shape matters as much as how it routes between shapes. A line that attaches to a fixed connection point - a specific spot on the shape's border - stays put as you move things, keeping the diagram tidy; a line attached to the shape as a whole (a floating connection) re-picks the nearest point automatically, which is convenient but less predictable. Use fixed points when you want a connector to always leave from the bottom or arrive at the top for consistency across a diagram, and floating connections when you want lines to reroute sensibly as you rearrange.

Small habits compound into clean diagrams: keep arrowheads consistent so direction reads at a glance, avoid attaching many lines to the exact same point so they do not overlap into an unreadable knot, and let lines exit a shape on the side facing their destination. Build and refine your routing in Atlas Diagram Studio at /diagrams, where you can switch a connector's style, drag waypoints, snap to connection points, and run auto-layout to reset a tangle. For process-specific diagrams, the flowchart maker at /diagram-tools/flowchart-maker and the Mermaid editor at /diagram-tools/mermaid-editor apply these same routing principles, and the broader tool set lives at /diagram-tools.