Task 577: Add In-Plane Curvature to 3D Transfer Arcs

Status: DONE

Description

3D transfer arcs are straight-line chords between planets with only a vertical (z-height)

bump. Real orbital transfers curve around the Sun. The 2D SVG diagrams correctly show

curved arcs (using angular midpoint at average radius as Bezier control point), but the

3D viewer does not. This makes the 3D visualization look unrealistic and inconsistent

with the 2D diagrams.

Plan

1. Modify arc control point calculation in orbital-3d-viewer.js to add in-plane curvature

- Keep the existing z-height bump

- Add displacement toward the Sun side (inward from the chord midpoint)

- The control point should be at approximately the angular midpoint between departure

and arrival angles, at the average orbital radius

1. Apply to all three arc-building code paths:

- addTransferArc() (static scene)

- loadTimeline() orbit-based arcs

- loadTimeline() pre-defined arcs

1. Add tests verifying arc control points have in-plane displacement
2. Verify visually via E2E tests

Files

• ts/src/orbital-3d-viewer.js — arc rendering
• ts/src/orbital-3d-viewer-data.ts — test data structure
• ts/src/orbital-3d-viewer-data.test.ts — tests