Cosmos Engine

Emergent physics simulation at planetary scale.

10+ million particles forming composite structures with emergent properties. Stars that generate stellar wind from plasma dynamics. Planets with layered internal structure that deforms and fractures under tidal stress. Spacecraft that crumple and tear under impact -- not from damage models, but from physics.

Cosmos Engine is a design vision for a next-generation 3D particle simulation platform where complex phenomena emerge from simple physical rules. This repository contains the complete design documentation -- from mesoscale force models to GPU kernel architectures, from a Scheme-inspired scripting DSL to distributed computation strategies.

The Core Insight

Complexity emerges from simplicity. Rather than programming explicit behaviors for stars, planets, and collisions, Cosmos Engine defines a minimal set of physical interactions at the mesoscale:

• Gravity via Particle Mesh (O(N) FFT-based, toroidal topology, GPU-native)
• Contact forces via Hertzian spring-damper model
• Structural bonds via dynamic spring networks with fatigue and plastic deformation
• Thermal dynamics from kinetic energy distributions and radiation transfer
• Electromagnetic forces from charge distributions and plasma currents

From these building blocks, everything else emerges: stellar wind, tidal disruption, crater formation, atmospheric drag, phase transitions, orbital resonances, crystal growth, and phenomena we haven't anticipated.

Why Mesoscale?

Each Cosmos Engine particle represents a significant chunk of matter -- 1000 tons of asteroid rock, 1 km^3 of planetary mantle, millions of tons of stellar plasma. This is deliberate. Molecular forces (Lennard-Jones, Morse potentials) belong at the atomic scale. At Cosmos Engine's mesoscale, the emergent properties of molecular interactions are already baked into material properties: density, stiffness, breaking strength, thermal conductivity. See Scale Rationale for the full argument.

Design Documents

Core Physics

Document	Scope
Emergent Physics Design	Master reference -- 90-page LaTeX document covering all physics systems
Integration Methods	Symplectic integrators, adaptive timestep, multi-rate schemes
Soft Contact Forces	Hertzian contact model, spring-damper collision response
Spring System Design	Dynamic spring networks, material properties, fatigue
Virtual Spring Design	Material-based spring generation, automatic bonding
Material Spring System	Material types, phase transitions, thermal coupling
Gravity and Spatial Topology	Particle Mesh gravity, toroidal boundary conditions
Multi-Range Force System	Three-tier force ranges: contact, local, global
Restorative Orbits	Orbital stability and perturbation damping

Spatial Systems

Document	Scope
Spatial Indexing Design	Multi-resolution spatial hashing, neighbor queries
Boundary Detection	Surface detection, composite boundary identification

Composite Bodies & Stellar Physics

Document	Scope
Composite Bodies Design	Union-Find discovery, rigid body approximation
Emergent Composite System	Self-assembling structures from particle interactions
Merger and Fission	Body merging, fragmentation, mass redistribution
Temperature Dynamics	Thermal conduction, radiation, phase transitions
Black Hole Design	Formation, accretion, Hawking radiation, event horizons
Ephemeral Particles	Short-lived particles for effects (sparks, debris, radiation)

Particle Management

Document	Scope
Particle Budget	Scale analysis, LOD strategies, memory constraints
Pool Design	Stable-ID particle pools, free-list allocation

Scripting & Events

Document	Scope
DSL Specification	Scheme-inspired simulation scripting language
Event System	Lock-free event bus, zero-copy transport, channel routing

GPU & Performance

Document	Scope
GPU/CPU Optimization	CUDA kernels, SIMD backends, force calculation pipeline
Backend Architecture	Abstract backend interface, multi-GPU, hybrid CPU/GPU

Networking & Distribution

Document	Scope
Network and Observation	Multi-client observation, LOD streaming, event relay
Distributed Computation	Domain decomposition, latency, consistency challenges

Architecture

Document	Scope
Target Architecture	Target directory layout and module decomposition
Integration Architecture	How all subsystems compose into a unified pipeline
Integrated Physics Spatial	Physics + spatial indexing co-design
Graphics Viewer	Real-time visualization, LOD rendering, camera systems

Library Design

Document	Scope
Library Extraction Analysis	Which components are library-quality (Boost.Spatial proposal)
Refactoring Comparison	API design trade-offs for generic spatial hashing

Vision

Document	Scope
Future Vision	Where Cosmos Engine is headed and why it matters
Scale Rationale	Why mesoscale, not molecular

Building the Reference PDF

The master design document is a LaTeX file. Build it with:

cd docs
pdflatex emergent_physics_design.tex
pdflatex emergent_physics_design.tex   # second pass for TOC/refs

A pre-built PDF is included at docs/emergent_physics_design.pdf.

The Unified Simulation Loop

Everything in Cosmos Engine runs through one pipeline per frame:

1. Particles generate fields -- mass distributions create gravity fields (PM grid), kinetic energy creates temperature fields, charge creates EM fields
2. Fields affect particles -- each particle samples all fields at its 3D position, accumulating forces from gradients
3. Forces update particles -- symplectic integration (velocity Verlet or higher-order) preserves long-term energy conservation
4. Contact resolution -- spatial hash detects overlapping particles, spring-damper model resolves penetration
5. Structures evolve -- spring networks stretch, compress, and break; new bonds form when particles come into sustained contact
6. Properties emerge -- temperature, pressure, angular momentum, material phase arise from collective particle behavior

This loop runs at 60+ FPS on 10M+ particles via GPU-accelerated Particle Mesh gravity and multi-resolution spatial hashing.