Task 607: 3D Viewer Target Body Collision Trajectory Fix

Status: DONE

Summary

Human directive: 土星→天王星接近軌道などがターゲット天体に直接突っ込むような軌道になっており、可視化上も突っ込んでいるように見える。

Transfer trajectories (especially Saturn→Uranus approach) appeared to collide directly with the target body because offsetFromPlanet used PLANET_RADII base values (Saturn: 0.35, Uranus: 0.25) instead of the actual rendered sphere radii in local scenes (Saturn: 0.5, Uranus: 0.4). For Uranus, the offset was 0.375 — inside the 0.4 sphere.

Root Cause

PLANET_RADII stores base display radii, but local scene central bodies override these with larger values in orbital-3d-viewer-data.ts. The offsetFromPlanet function didn't know about these overrides, so arc endpoints could land inside the planet sphere.

Fix

1. orbital-3d-viewer-data.ts: Added optional explicitRadius parameter to offsetFromPlanet() so callers can pass the actual rendered radius.
2. orbital-3d-viewer.js: Added _planetDisplayRadii map populated during scene build (from planet data), used by offsetFromPlanet to get the correct sphere radius. Falls back to mesh geometry, then PLANET_RADII.
3. Tests: Added 2 tests verifying explicit radius usage and that offset clears actual sphere radius for Saturn (0.5) and Uranus (0.4).

Dependencies

• Task 584 (DONE) — parking orbit visualization
• Task 579 (DONE) — orbital insertion alignment

Key Files

• ts/src/orbital-3d-viewer.js — collision offset fix (scene build populates _planetDisplayRadii)
• ts/src/orbital-3d-viewer-data.ts — offsetFromPlanet accepts explicit radius
• ts/src/orbital-3d-viewer-data.test.ts — 2 new tests