How to Read This Book

The FCP method, the notation, the running lab, and what you need to know before starting.

This book is organized so that you can read it three different ways, and all three are legitimate.

The three passes

Every chapter makes three passes over its subject, in this order:

Reading paths

• The full path — read straight through. Part I builds the geometry, Parts II–III the planners, Part IV the uncertainty a planner must live with, Part V dynamics and constraints, Part VI learning and the integrated stack.
• The path-planning path (Choset's own suggestion, updated) — Chapters 4, 5, 6, 7, 8, 11, 12, 13, then 10. The shortest route from "what is a configuration space" to "what a modern planning library actually runs".
• The mobile-robotics path — Chapters 2, 3, 6, 7, 8, 9, 16, 21, 23.
• The mechanical-systems path — Chapters 4, 5, 17, 18, 19, 20, 21.
• The builder's path — skim the Foundation sections, play with every widget, and implement the Practical section of each chapter. The exercises marked P are the spine of this route.

The running lab

Three robots and three worlds recur throughout the book, so that every new method can be compared against the last on identical ground.

Rusty is a differential-drive rover with a range sensor — the same robot as in the sister volume. Rusty lives in the Apartment, a 2-D floorplan with rooms, doorways, and a long corridor. For most of Parts I–IV Rusty is treated as a disc, which makes its configuration space a plane.

Reach is a planar two-link arm (with a three-link variant for redundancy). Reach works at the Workbench, a table with polygonal obstacles. Its configuration space is a torus, which is why it is the book's canonical example whenever topology matters, and its dynamics carry Part V.

Hitch is a car-like robot that can pull a trailer. Hitch lives in the Lot, a parking lot with bays and pillars, and cannot move sideways — which is the whole subject of Chapters 20 and 21.

All three are built in Chapter 2 and act together in Chapter 23.

Notation and color

The book follows the notation of Choset et al. so that readers can move between this text and the literature without translating: $\Q$ for the configuration space, $\QO_i$ for a C-obstacle, $\Qfree$ for free space, $c : [0,1] \to \Qfree$ for a path. The notation reference lists every symbol.

One convention is worth internalizing before you start, because it runs through the prose, the equations, the figures, and the code comments alike:

• Start
• Goal
• Obstacle
• C-obstacle
• Roadmap / tree
• Path
• Robot

Green is always where you start and red is always where you want to be. Slate is a thing in the world; amber is the set of configurations that would make the robot touch it. Blue is what a planner has explored — a roadmap, a tree, a wavefront. Purple is the path it chose. Orange is the robot itself, and the trajectory it actually executed.

Where a belief appears (Chapters 15–16 and the capstone), the sister book's five estimation colors are used unchanged, so a reader of both books never has to relearn a color.

On the Rust

The book uses Rust because motion planning is exactly the kind of code where the type system earns its keep: a configuration on a torus cannot be passed where a rigid-body pose is expected, a path cannot be handed to a controller that needs a trajectory, and there is no garbage collector to interfere with a planning loop.

You do not need to know Rust before starting. What you need is patience with a compiler that is stricter than you are used to, and the willingness to read a type signature as documentation. The crates the book relies on — nalgebra, parry2d, petgraph, rand — are introduced when they are first needed.