Define End Point and Links.
P₁ and P₂ auto-place on the perpendicular bisectors of joint travel. Drag either pivot to refine; click any vertex to reassign A or B. Editing the end pose re-derives the linkage automatically.
Coupler — rigid body
Link 1, Link 2 — bars
P₁, P₂ — ground pivots
A, B — joints (coupler)
Motion arcs / ghost poses
Link 1 (P₁–A) = 100.9 px
Link 2 (P₂–B) = 102.5 px
Coupler (A–B) = 120.0 px
Link 1 (P₁–A′) = 100.9 px
Link 2 (P₂–B′) = 102.5 px
Coupler (A′–B′) = 120.0 px