About High-Fidelity Water Surface and Beaufort Scale Simulation Setup

[CooolWindS]

Hi @Abanesjo ,
First of all, thank you for developing and maintaining the ATRON project. It has been very helpful for our current research and development work, especially in understanding how ship and UAV-related simulation environments can be constructed in Isaac Sim.

I would like to ask a question regarding the High-Fidelity Simulation part of the project. In the project description, I noticed that high-fidelity water surface environments and Beaufort Scale-based sea state settings are mentioned. However, I could not find detailed instructions, configuration steps, or examples in the current repository explaining how to use or reproduce these features.

Since I have limited experience in building high-fidelity water surfaces, vessel motion, and sea state simulation environments in Isaac Sim, I would like to ask whether the current project already provides any documentation, examples, or configuration files for the High-Fidelity Simulation or Beaufort Scale environment settings.

If these resources are not currently available, may I ask whether there are any plans to update the repository with related documentation or examples in the future? Also, if convenient, I would greatly appreciate any brief guidance on which part of the project, configuration files, or external references I should look into first.

I appreciate your time and look forward to your reply.
Thank you!

[Abanesjo]

Hi, you can check the USD file in the releases for the lake world

https://github.com/RISC-NYUAD/ATRON/releases/tag/v1

For performance reasons the sensor publishing to ROS2 is disabled by default. If you want to enable it, you can activate the ActionGraph prim at /USV/Graph/Sensors

The buoyance seems to be broken on isaac sim 6.0 currently, but it works fine on isaac sim 5.1.

If you want to modify the beaufort scale / waves, it's a bit more involved. You can edit the script nodes under /USV/Graph/buoyancy. The Action graph looks like

There are four script node blocks, one acting on four different corners of the boat to generate sinusoidal waves. The script looks like below. You can edit N, k_min/k_max, a_min/a_max.

import math
import numpy as np

WATER_DENSITY = 1000.0
GRAVITY = 9.8
WAVES = []

def setup(db):
    global WAVES
    if WAVES:
        return

    rng = np.random.RandomState(1234)
    N = 6
    k_min, k_max = 0.2, 1.0
    a_min, a_max = 0.01, 0.05

    for _ in range(N):
        k = rng.uniform(k_min, k_max)
        theta = rng.uniform(0.0, 2.0 * math.pi)
        omega = math.sqrt(GRAVITY * k)
        phi = rng.uniform(0.0, 2.0 * math.pi)
        a = rng.uniform(a_min, a_max)
        ax = k * math.cos(theta)
        ay = k * math.sin(theta)
        WAVES.append((a, ax, ay, omega, phi))

def wave_height(x, y, t):
    h = 0.0
    for a, ax, ay, omega, phi in WAVES:
        phase = ax * x + ay * y - omega * t + phi
        h += a * math.cos(phase)
    return h

def compute(db):
    area = db.inputs.area
    height = db.inputs.height

    pos = db.inputs.position   # [x, y, z]
    x, y, z = pos[0], pos[1], pos[2]
    t = db.inputs.time

    eta = wave_height(x, y, t)
    z_rel = z - eta

    submerged_height = calculate_submerged_height(z_rel, height)
    submerged_volume = area * submerged_height
    buoyancy_force = WATER_DENSITY * submerged_volume * GRAVITY

    db.outputs.x_force = 0.0
    db.outputs.y_force = 0.0
    db.outputs.z_force = buoyancy_force
    db.outputs.buoyancy_force = [0.0, 0.0, buoyancy_force]

def calculate_submerged_height(z_rel, height):
    c = height / 2.0
    if z_rel >= c:
        return 0.0
    elif z_rel <= -c:
        return height
    else:
        return c - z_rel

N affects the number of wave components, k affects the wavelength, a affects the wave amplitude.