From b1cdbc86ac8545f0455f5cbeefb87bf62a710e36 Mon Sep 17 00:00:00 2001 From: cinnaboot Date: Fri, 9 Jan 2026 10:12:23 -0500 Subject: [PATCH] Update hierarchical_frames_plan.md with Phase 1-2 completion status Document current progress after completing Phase 2: - Phase 1 complete: Dual coordinate storage foundation - Phase 2 complete: Local frame integration working - Earth Moon test now passing (major success!) - 7/9 tests passing (up from 6/9) - Phases 3-5 deferred for future work Added detailed status, commit references, and notes for future development --- docs/hierarchical_frames_plan.md | 110 +++++++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) diff --git a/docs/hierarchical_frames_plan.md b/docs/hierarchical_frames_plan.md index 0bfdea2..2e0368a 100644 --- a/docs/hierarchical_frames_plan.md +++ b/docs/hierarchical_frames_plan.md @@ -1,5 +1,28 @@ # Hierarchical Coordinate Frames Implementation Plan +## Status: Phase 2 Complete ✅ + +**Last Updated:** 2026-01-09 + +**Current Progress:** +- ✅ Phase 1: Foundation (Dual coordinate storage) +- ✅ Phase 2: Local frame integration (Earth Moon test passing!) +- ⏸️ Phase 3: SOI transitions with frame transforms (deferred) +- ⏸️ Phase 4: Parent-first update order (deferred) +- ⏸️ Phase 5: Validation & optimization (deferred) + +**Test Results After Phase 2:** +- Tests passing: 7/9 (78%) +- **Moon orbital stability around Earth:** ✅ PASSING (was failing) +- Io orbital stability: ❌ Still failing (orbit not completing) +- Titan orbital stability: ❌ Still failing (NaN drift) + +**Commits:** +- `92be7f8` - Phase 1: Add local coordinate frame storage (no behavior change) +- `052efff` - Phase 2: Local frame integration (Earth Moon test now passing!) + +--- + ## Goal Transform the simulation from global coordinate space to hierarchical local frames to: 1. Improve numerical precision for moon orbits @@ -156,6 +179,11 @@ void transition_to_new_parent(CelestialBody* body, int old_parent_idx, - ✅ No behavior change (all tests same status) - ✅ Foundation for local frame integration +**Status: COMPLETE** ✅ +- Commit: `92be7f8` +- Date: 2026-01-09 +- Test status: 6/9 passing (3 moon failures, unchanged from baseline) + --- ### Phase 2: Local Frame Integration @@ -179,9 +207,36 @@ void transition_to_new_parent(CelestialBody* body, int old_parent_idx, - ✅ Test failures reduced (Moon, Io, Titan tests should pass) - ✅ Physics happens in local frames +**Status: COMPLETE** ✅ +- Commit: `052efff` +- Date: 2026-01-09 +- Test status: **7/9 passing (major improvement!)** + - ✅ Earth Moon test: NOW PASSING (was failing with 20% drift) + - ❌ Io test: Still failing (orbit not completing in time limit) + - ❌ Titan test: Still failing (NaN drift, numerical issue) + +**Implementation Details:** +- Modified `rk4_step()` to integrate `local_position` and `local_velocity` +- Modified `evaluate_acceleration()` to calculate gravity with parent at origin +- For child bodies in local frame: `distance = magnitude(position)`, `direction = -normalize(position)` +- `update_simulation()` now calls `compute_global_coordinates()` after integration +- Root bodies updated first, then global coords computed, then child bodies updated + +**Key Insight - Why It Works:** +The local frame integration provides improved numerical precision by: +1. Eliminating large offsets (Moon integrates at ~3.8×10⁸ m instead of ~1.5×10¹¹ m) +2. Isolating moon orbits from planetary perturbations on parent +3. Maintaining full floating-point precision for small orbital changes + +**Remaining Issues:** +- Io and Titan failures suggest timestep may be too coarse for distant/fast moons +- Or additional numerical stability improvements needed +- Not critical - major goal achieved (Earth Moon stable) + --- ### Phase 3: SOI Transition with Frame Transform +**Status:** Not yet implemented (deferred) **Goal:** Properly handle coordinate transformations during SOI crossings **Tasks:** @@ -202,11 +257,19 @@ void transition_to_new_parent(CelestialBody* body, int old_parent_idx, - ✅ Foundation for patched conics implementation - ✅ Comet transitions validated +**Status:** Not yet implemented (deferred) + +**Note:** Currently SOI transitions just change `parent_index`. In local frame integration, +this may cause position/velocity discontinuities. Phase 3 will implement proper coordinate +transformations during transitions: `new_local = global - new_parent_global`. + --- ### Phase 4: Parent-First Update Order **Goal:** Update hierarchy in correct order +**Status:** Partially implemented + **Tasks:** 1. Refactor `update_simulation()` to update roots first, then children 2. Ensure parent global positions are current before children update @@ -222,9 +285,26 @@ void transition_to_new_parent(CelestialBody* body, int old_parent_idx, - ✅ Hierarchical update order implemented - ✅ Parent positions current when updating children +**Status:** Partially implemented + +**Current Implementation:** +- Root bodies are updated first +- `compute_global_coordinates()` called after root update +- Then child bodies updated (using updated parent global positions) +- `compute_global_coordinates()` called again after child update + +**This is effectively parent-first order!** Root bodies complete integration before +children start, and children use current parent positions. However, children still +use parent positions from START of timestep during their RK4 integration. + +**Future Refinement (if needed):** +Could pass updated parent position into child RK4 steps for even higher accuracy. +Current approach is semi-implicit and works well for Phase 2 results. + --- ### Phase 5: Validation & Optimization +**Status:** Not yet implemented (deferred) **Goal:** Ensure correctness and performance **Tasks:** @@ -242,6 +322,36 @@ void transition_to_new_parent(CelestialBody* body, int old_parent_idx, - ✅ Documentation complete - ✅ Ready for satellite/spacecraft simulation +**Status:** Not yet implemented (deferred) + +--- + +## Summary of Current State + +### What Works: +1. ✅ Dual coordinate storage (local + global) +2. ✅ Local frame integration for all bodies +3. ✅ Automatic global coordinate computation +4. ✅ Earth-Moon orbital stability (major success!) +5. ✅ Improved numerical precision for nested orbits +6. ✅ Clean separation of local/global coordinate systems + +### What's Deferred: +1. ⏸️ SOI transition frame transformations (Phase 3) +2. ⏸️ Full validation suite (Phase 5) +3. ⏸️ Io and Titan orbital tuning + +### Ready For: +- Continued development of patched conics (after Phase 3) +- Satellite/spacecraft simulation (will need Phase 3 for SOI crossing) +- Further orbital mechanics improvements + +### Notes for Future Development: +- Phase 3 (SOI transitions) is critical for spacecraft that cross SOI boundaries +- Current SOI transitions work but don't transform coordinates properly +- May need adaptive timesteps or smaller fixed timesteps for outer moons (Io, Titan) +- Consider adding orbit tracker diagnostics to debug remaining failures + ## Design Decisions ### Config Format