"""Example 5: Rapier Physics Simulation (Requires Rapier Service)
This example demonstrates the Rapier simulation tools for rigid-body physics.
REQUIREMENTS:
This example uses the public Rapier service at https://rapier.chukai.io
To use a local service instead:
export RAPIER_SERVICE_URL=http://localhost:9000
The analytic examples (00-04) work without any external services.
WHAT THIS DEMONSTRATES:
- Creating a physics simulation world
- Adding rigid bodies (boxes, spheres, capsules)
- Stepping the simulation forward in time
- Recording trajectories of objects
- Collision detection through simulation
- Gravity and realistic physics
"""
# IMPORTANT: Set environment variable BEFORE any imports
import os
if "RAPIER_SERVICE_URL" not in os.environ:
os.environ["RAPIER_SERVICE_URL"] = "https://rapier.chukai.io"
import asyncio
from chuk_mcp_physics.providers.factory import get_provider
from chuk_mcp_physics.models import (
SimulationConfig,
RigidBodyDefinition,
BodyType,
ShapeType,
)
async def example_bouncing_ball():
"""Simulate a ball bouncing on the ground."""
print("\n" + "=" * 70)
print("EXAMPLE 1: Bouncing Ball")
print("=" * 70)
# Get Rapier provider (will try to connect to service)
provider = get_provider("rapier")
try:
# 1. Create simulation world with gravity
print("\n1️⃣ Creating simulation world...")
config = SimulationConfig(
gravity=[0, -9.81, 0], # Earth gravity pointing down
dimensions=3,
dt=0.016, # 60 FPS timestep
)
sim = await provider.create_simulation(config)
print(f" ✓ Created simulation: {sim.sim_id}")
# 2. Add ground plane (static body)
print("\n2️⃣ Adding ground plane...")
ground = RigidBodyDefinition(
id="ground",
kind=BodyType.STATIC,
shape=ShapeType.BOX,
size=[100.0, 0.1, 100.0], # Wide, thin platform
position=[0.0, 0.0, 0.0],
)
await provider.add_body(sim.sim_id, ground)
print(" ✓ Ground added at y=0")
# 3. Add bouncing ball above ground
print("\n3️⃣ Adding ball 10m above ground...")
ball = RigidBodyDefinition(
id="ball",
kind=BodyType.DYNAMIC,
shape=ShapeType.SPHERE,
size=[0.5], # 0.5m radius
mass=1.0,
position=[0.0, 10.0, 0.0],
restitution=0.8, # 80% bounce
)
await provider.add_body(sim.sim_id, ball)
print(" ✓ Ball added (mass=1kg, radius=0.5m, bounce=0.8)")
# 4. Record trajectory for 3 seconds (180 frames at 60fps)
print("\n4️⃣ Simulating 3 seconds of bouncing...")
trajectory = await provider.record_trajectory(
sim.sim_id,
"ball",
steps=180,
)
print(
f" ✓ Recorded {trajectory.meta.num_frames} frames over {trajectory.meta.total_time:.2f}s"
)
# 5. Analyze bounces
print("\n5️⃣ Bounce Analysis:")
bounces = []
for i in range(1, len(trajectory.frames)):
prev_frame = trajectory.frames[i - 1]
curr_frame = trajectory.frames[i]
# Detect bounce: velocity changes from down to up
if prev_frame.velocity[1] < 0 and curr_frame.velocity[1] > 0:
bounces.append(
{
"time": curr_frame.time,
"height": curr_frame.position[1],
"velocity": curr_frame.velocity[1],
}
)
print(f" Detected {len(bounces)} bounces:")
for i, bounce in enumerate(bounces[:5], 1): # Show first 5
print(
f" Bounce {i}: t={bounce['time']:.2f}s, h={bounce['height']:.2f}m, v={bounce['velocity']:.1f}m/s"
)
# 6. Cleanup
await provider.destroy_simulation(sim.sim_id)
print("\n ✓ Simulation cleaned up")
except Exception as e:
print(f"\n❌ Error: {e}")
service_url = os.environ.get("RAPIER_SERVICE_URL", "https://rapier.chukai.io")
print(f"\nCannot connect to Rapier service at {service_url}")
print("Using public service: https://rapier.chukai.io (default)")
print("For local service: export RAPIER_SERVICE_URL=http://localhost:9000")
async def example_collision_simulation():
"""Simulate two objects colliding."""
print("\n" + "=" * 70)
print("EXAMPLE 2: Head-On Collision")
print("=" * 70)
provider = get_provider("rapier")
try:
# Create simulation
print("\n1️⃣ Creating simulation world...")
config = SimulationConfig(
gravity=[0, 0, 0], # No gravity (space collision)
dimensions=3,
dt=0.01, # 100 FPS for precise collision detection
)
sim = await provider.create_simulation(config)
print(f" ✓ Created simulation: {sim.sim_id}")
# Add two boxes moving toward each other
print("\n2️⃣ Adding two boxes on collision course...")
box1 = RigidBodyDefinition(
id="box1",
kind=BodyType.DYNAMIC,
shape=ShapeType.BOX,
size=[1.0, 1.0, 1.0],
mass=5.0,
position=[-10.0, 0.0, 0.0],
velocity=[5.0, 0.0, 0.0], # Moving right at 5 m/s
restitution=0.5, # 50% elastic collision
)
await provider.add_body(sim.sim_id, box1)
print(" ✓ Box 1: mass=5kg, position=(-10, 0, 0), velocity=(5, 0, 0)")
box2 = RigidBodyDefinition(
id="box2",
kind=BodyType.DYNAMIC,
shape=ShapeType.BOX,
size=[1.0, 1.0, 1.0],
mass=3.0,
position=[10.0, 0.0, 0.0],
velocity=[-5.0, 0.0, 0.0], # Moving left at 5 m/s
restitution=0.5,
)
await provider.add_body(sim.sim_id, box2)
print(" ✓ Box 2: mass=3kg, position=(10, 0, 0), velocity=(-5, 0, 0)")
# Simulate collision
print("\n3️⃣ Simulating 4 seconds...")
print("\n Time | Box1 Position | Box1 Velocity | Box2 Position | Box2 Velocity")
print(" " + "-" * 75)
for step in range(0, 400, 40): # Show every 0.4 seconds
state = await provider.step_simulation(sim.sim_id, steps=40)
box1_state = next(b for b in state.bodies if b.id == "box1")
box2_state = next(b for b in state.bodies if b.id == "box2")
print(
f" {state.time:4.1f}s | "
f"{box1_state.position[0]:6.1f} | "
f"{box1_state.velocity[0]:6.1f} | "
f"{box2_state.position[0]:6.1f} | "
f"{box2_state.velocity[0]:6.1f}"
)
await provider.destroy_simulation(sim.sim_id)
print("\n ✓ Simulation cleaned up")
except Exception as e:
print(f"\n❌ Error: {e}")
service_url = os.environ.get("RAPIER_SERVICE_URL", "https://rapier.chukai.io")
print(f"\nCannot connect to Rapier service at {service_url}")
print("Using public service: https://rapier.chukai.io (default)")
print("For local service: export RAPIER_SERVICE_URL=http://localhost:9000")
async def example_stacking_boxes():
"""Simulate a tower of boxes under gravity."""
print("\n" + "=" * 70)
print("EXAMPLE 3: Stacking Boxes (Tower Stability)")
print("=" * 70)
provider = get_provider("rapier")
try:
print("\n1️⃣ Creating simulation world...")
config = SimulationConfig(
gravity=[0, -9.81, 0],
dimensions=3,
dt=0.016,
)
sim = await provider.create_simulation(config)
print(f" ✓ Created simulation: {sim.sim_id}")
# Add ground
print("\n2️⃣ Adding ground...")
ground = RigidBodyDefinition(
id="ground",
kind=BodyType.STATIC,
shape=ShapeType.BOX,
size=[20.0, 0.1, 20.0],
position=[0.0, 0.0, 0.0],
)
await provider.add_body(sim.sim_id, ground)
print(" ✓ Ground added")
# Stack 5 boxes
print("\n3️⃣ Stacking 5 boxes vertically...")
box_height = 1.0
for i in range(5):
box = RigidBodyDefinition(
id=f"box_{i}",
kind=BodyType.DYNAMIC,
shape=ShapeType.BOX,
size=[1.0, box_height, 1.0],
mass=2.0,
position=[0.0, 0.5 + i * box_height, 0.0],
friction=0.5,
restitution=0.1, # Low bounce
)
await provider.add_body(sim.sim_id, box)
print(" ✓ 5 boxes stacked (2kg each)")
# Let physics settle
print("\n4️⃣ Letting tower settle for 5 seconds...")
for i in range(5):
await provider.step_simulation(sim.sim_id, steps=60) # 1 second
state = await provider.get_simulation_state(sim.sim_id)
# Check top box height
top_box = next(b for b in state.bodies if b.id == "box_4")
print(f" t={state.time:.1f}s: Top box height = {top_box.position[1]:.3f}m")
await provider.destroy_simulation(sim.sim_id)
print("\n ✓ Simulation cleaned up")
except Exception as e:
print(f"\n❌ Error: {e}")
service_url = os.environ.get("RAPIER_SERVICE_URL", "https://rapier.chukai.io")
print(f"\nCannot connect to Rapier service at {service_url}")
print("Using public service: https://rapier.chukai.io (default)")
print("For local service: export RAPIER_SERVICE_URL=http://localhost:9000")
async def main():
"""Run all Rapier simulation examples."""
print("=" * 70)
print("RAPIER PHYSICS SIMULATION EXAMPLES")
print("=" * 70)
service_url = os.environ.get("RAPIER_SERVICE_URL", "https://rapier.chukai.io")
print(f"\nThese examples use the Rapier service at: {service_url}")
print("(Public service available, or set RAPIER_SERVICE_URL for local testing)")
print("\nIf you want to run examples without external services,")
print("use examples 00-04 which use the built-in analytic provider.")
try:
# Test connection first
provider = get_provider("rapier")
# This will fail if service isn't running
test_config = SimulationConfig(gravity=[0, -9.81, 0], dimensions=3)
await provider.create_simulation(test_config)
print("\n✓ Rapier service is running! Proceeding with examples...\n")
except Exception as e:
print(f"\n❌ Cannot connect to Rapier service: {e}")
print("\nPossible solutions:")
print(" 1. Check your internet connection (public service at https://rapier.chukai.io)")
print(" 2. Run analytic examples instead (00-04)")
print(" 3. Run local Rapier service: export RAPIER_SERVICE_URL=http://localhost:9000")
return
# Run examples
await example_bouncing_ball()
await example_collision_simulation()
await example_stacking_boxes()
print("\n" + "=" * 70)
print("All examples completed successfully!")
print("=" * 70)
if __name__ == "__main__":
asyncio.run(main())
