# Particles Physics

> Physics simulation for particle systems—forces (gravity, wind, drag), attractors/repulsors, velocity fields, turbulence, and collision. Use when particles need realistic or artistic motion, swarm behavior, or field-based animation.

- **Type:** Skill
- **Install:** `agentstack add skill-bbeierle12-skill-mcp-claude-particles-physics`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [Bbeierle12](https://agentstack.voostack.com/s/bbeierle12)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [Bbeierle12](https://github.com/Bbeierle12)
- **Source:** https://github.com/Bbeierle12/Skill-MCP-Claude/tree/main/skills/particles-physics

## Install

```sh
agentstack add skill-bbeierle12-skill-mcp-claude-particles-physics
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Particle Physics

Apply forces, fields, and constraints to create dynamic particle motion.

## Quick Start

```tsx
// Simple gravity + velocity
useFrame((_, delta) => {
  for (let i = 0; i  0) {
      const dragForce = coefficient * speed * speed;
      const factor = Math.max(0, 1 - (dragForce * delta) / speed);
      
      velocities[i * 3] *= factor;
      velocities[i * 3 + 1] *= factor;
      velocities[i * 3 + 2] *= factor;
    }
  }
}
```

## Attractors & Repulsors

### Point Attractor

```tsx
function applyAttractor(
  velocities: Float32Array,
  positions: Float32Array,
  count: number,
  attractorPos: THREE.Vector3,
  strength: number,  // Positive = attract, negative = repel
  delta: number
) {
  for (let i = 0; i  0.1) {  // Avoid division by zero
      // Inverse square falloff
      const force = strength / distSq;
      
      velocities[i * 3] += (dx / dist) * force * delta;
      velocities[i * 3 + 1] += (dy / dist) * force * delta;
      velocities[i * 3 + 2] += (dz / dist) * force * delta;
    }
  }
}
```

### Orbit Attractor

```tsx
function applyOrbitAttractor(
  velocities: Float32Array,
  positions: Float32Array,
  count: number,
  center: THREE.Vector3,
  orbitStrength: number,
  pullStrength: number,
  delta: number
) {
  for (let i = 0; i  0.1) {
      // Tangential force (orbit)
      const tx = -dz / dist;
      const tz = dx / dist;
      
      velocities[i * 3] += tx * orbitStrength * delta;
      velocities[i * 3 + 2] += tz * orbitStrength * delta;
      
      // Radial force (pull toward center)
      velocities[i * 3] -= (dx / dist) * pullStrength * delta;
      velocities[i * 3 + 1] -= (dy / dist) * pullStrength * delta;
      velocities[i * 3 + 2] -= (dz / dist) * pullStrength * delta;
    }
  }
}
```

### Multiple Attractors

```tsx
interface Attractor {
  position: THREE.Vector3;
  strength: number;
  radius: number;  // Influence radius
}

function applyAttractors(
  velocities: Float32Array,
  positions: Float32Array,
  count: number,
  attractors: Attractor[],
  delta: number
) {
  for (let i = 0; i  0.1 && dist  0.1) {
      // Tangent direction (cross product with axis)
      const tx = axis.y * pz - axis.z * py;
      const ty = axis.z * px - axis.x * pz;
      const tz = axis.x * py - axis.y * px;
      
      const tLen = Math.sqrt(tx * tx + ty * ty + tz * tz);
      const force = strength * Math.exp(-dist * falloff);
      
      velocities[i * 3] += (tx / tLen) * force * delta;
      velocities[i * 3 + 1] += (ty / tLen) * force * delta;
      velocities[i * 3 + 2] += (tz / tLen) * force * delta;
    }
  }
}
```

## Turbulence

### Simplex-Based Turbulence

```glsl
// GPU turbulence in vertex shader
vec3 turbulence(vec3 p, float time, float scale, int octaves) {
  vec3 result = vec3(0.0);
  float amplitude = 1.0;
  float frequency = scale;
  
  for (int i = 0; i  radius : dist  0) {
      const nx = dx / dist;
      const ny = dy / dist;
      const nz = dz / dist;
      
      // Move to surface
      const targetDist = inside ? radius : radius;
      positions[i * 3] = center.x + nx * targetDist;
      positions[i * 3 + 1] = center.y + ny * targetDist;
      positions[i * 3 + 2] = center.z + nz * targetDist;
      
      // Reflect velocity
      const dot = velocities[i * 3] * nx + velocities[i * 3 + 1] * ny + velocities[i * 3 + 2] * nz;
      velocities[i * 3] = (velocities[i * 3] - 2 * dot * nx) * bounce;
      velocities[i * 3 + 1] = (velocities[i * 3 + 1] - 2 * dot * ny) * bounce;
      velocities[i * 3 + 2] = (velocities[i * 3 + 2] - 2 * dot * nz) * bounce;
    }
  }
}
```

## Integration Methods

### Euler (Simple)

```tsx
// Fastest, least accurate
position += velocity * delta;
velocity += acceleration * delta;
```

### Verlet (Better for constraints)

```tsx
// Store previous position
const newPos = position * 2 - prevPosition + acceleration * delta * delta;
prevPosition = position;
position = newPos;
```

### RK4 (Most accurate)

```tsx
// Runge-Kutta 4th order (for high precision)
function rk4(position: number, velocity: number, acceleration: (p: number, v: number) => number, dt: number) {
  const k1v = acceleration(position, velocity);
  const k1x = velocity;
  
  const k2v = acceleration(position + k1x * dt/2, velocity + k1v * dt/2);
  const k2x = velocity + k1v * dt/2;
  
  const k3v = acceleration(position + k2x * dt/2, velocity + k2v * dt/2);
  const k3x = velocity + k2v * dt/2;
  
  const k4v = acceleration(position + k3x * dt, velocity + k3v * dt);
  const k4x = velocity + k3v * dt;
  
  return {
    position: position + (k1x + 2*k2x + 2*k3x + k4x) * dt / 6,
    velocity: velocity + (k1v + 2*k2v + 2*k3v + k4v) * dt / 6
  };
}
```

## File Structure

```
particles-physics/
├── SKILL.md
├── references/
│   ├── forces.md             # All force types
│   └── integration.md        # Integration methods comparison
└── scripts/
    ├── forces/
    │   ├── gravity.ts        # Gravity implementations
    │   ├── attractors.ts     # Point/orbit attractors
    │   └── fields.ts         # Flow/velocity fields
    └── collision/
        ├── planes.ts         # Plane collision
        └── shapes.ts         # Sphere, box collision
```

## Reference

- `references/forces.md` — Complete force implementations
- `references/integration.md` — When to use which integration method

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [Bbeierle12](https://github.com/Bbeierle12)
- **Source:** [Bbeierle12/Skill-MCP-Claude](https://github.com/Bbeierle12/Skill-MCP-Claude)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** yes
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-bbeierle12-skill-mcp-claude-particles-physics
- Seller: https://agentstack.voostack.com/s/bbeierle12
- Browse the marketplace: https://agentstack.voostack.com/browse

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