Fusion 360: How to Fully Define Splines Using Control Handle Dimensions and Angles*

Struggling with blue, under-defined splines in Fusion 360? This quick walkthrough shows how to fully constrain a spline by properly constructing it first, then locking it down with the right dimensions. You’ll learn why fewer control points usually create smoother, more controllable curves, and exactly what to dimension so your spline snaps from blue to black (fully defined). You’ll see the core spline constraints in Fusion 360: Control handle length (arm length) Control handle angle Control point location in space (only when needed) Timestamps 00:02 Splines in Fusion 360 and why they’re often under-defined 00:20 Before constraining: make sure the spline is built correctly 00:40 Why fewer control points usually means a better spline 00:54 What you must define to fully constrain a spline 01:06 Dimensioning control handle (arm) lengths 01:24 Defining control handle angles 01:39 When the spline becomes fully defined (blue to black, padlock) 01:52 Why extra control points can reduce smoothness and add more constraints 02:07 Quick recap: the 3 things to define for fully constrained splines