b2KIT

Locus Tracer

Trace loci of points under geometric constraints. Explore ellipse, parabola, and cardioid generation through linkage mechanisms.

Tested tool guide Tested browser tools Checked August 16, 2026

What Locus Tracer does and how it behaves

Locus Tracer follows a marked point as an ellipse, parabola, or cardioid mechanism changes configuration. Instead of presenting only a finished curve, it relates the accumulated path to the linkage and geometric constraints that move the point. The key distinction is between one displayed position and the locus: the current marker is a single allowed position, while the locus is the complete set of positions allowed by the motion. A recognizable outline is therefore the result of the constraint, not an independently drawn graph.

How the result is produced

1

From configuration to locus

Each configuration satisfies the mechanism's geometric constraints, such as fixed pivots, guide lines, or unchanged link lengths. The tracked point contributes one position for that configuration. Continuing the motion reveals the collection of allowable positions. A single configuration explains where the point is now; the accumulated trace answers where it can be while the same constraints remain in force.

2

Recognizing the named curves

The named results have standard geometric descriptions. An ellipse has a constant sum of distances to two foci. A parabola consists of points equidistant from a focus and a directrix. A cardioid can be generated by a point on a circle rolling around a fixed circle of equal radius. The displayed linkage is a construction of a curve, not its mathematical definition.

Good uses

  • Demonstrating in a geometry lesson how successive positions of one constrained point build a complete ellipse, parabola, or cardioid.
  • Reviewing a linkage construction before deriving the corresponding curve with coordinates, distances, or parametric equations.
  • Comparing how different geometric constraints produce a closed oval, an open conic branch, or a cusped heart-shaped locus.

Limits and checks

  • Do not confuse the moving marker with the answer. Its current location is one member of the locus, not the complete traced set.
  • A shape that looks like the expected curve on screen is not an algebraic proof that every traced point satisfies the curve's defining relation.
  • Apparent speed along the trace is a property of how the mechanism is moved. Speed and timing are not defining properties of an ellipse, parabola, or cardioid.

Common questions

Why can the linkage move while the resulting locus remains the same curve?

The linkage changes configuration, but its fixed geometric relationships remain in force. Those relationships restrict the tracked point to a particular set of possible locations. Each configuration supplies another location from that same set, so the marker moves while the accumulated locus retains its ellipse, parabola, or cardioid form.

Can I treat the displayed trace as an equation or geometric proof?

No, not by itself. The trace is a visual account of positions produced by the mechanism. It can suggest the intended curve and clarify the construction, but an exact conclusion requires a derivation from the constraints, such as proving a focal-distance relation or obtaining coordinates that satisfy the relevant equation.

References and verification

The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.

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