Programatic Terrain selection

[Danfoa]

Define a terrain optional callback method defining the assets, bodies and geometries composing the ground.

We can define a suit of reference terrains, perlin, flat, ...., and enable the user to define its own. Something similar to what is done here:

gym-quadruped/gym_quadruped/utils/mujoco/terrain.py

Lines 26 to 94 in 78a016e

	def add_perlin_heightfield(
	asset: xml_et.Element,
	worldbody: xml_et.Element,
	position: List[float] = (0.0, 0.0, 0.0), # position
	euler_xyz: List[float] = (0.0, 0.0, 0.0), # attitude
	size: List[float] = (1.0, 1.0), # width and length of the generated field in meters
	max_height: float = 0.4, # Maximum height value of the heightfield in meters
	min_height: float = 0.001, # Minimum height value of the heightfield in meters
	image_width: int = 128, # height field image size
	img_height: int = 128,
	smooth: float = 100.0, # smooth scale
	perlin_octaves: int = 6, # perlin noise parameter
	perlin_persistence: float = 0.5,
	perlin_lacunarity: float = 2.0,
	output_hfield_image: str = "height_field.png") -> None:
	"""
	Adds a Perlin noise-based heightfield to the scene.
	Args:
	asset (xml_et.Element): The asset element of the XML.
	worldbody (xml_et.Element): The worldbody element of the XML.
	position (List[float]): Position of the heightfield [x, y, z].
	euler_xyz (List[float]): Euler angles for the heightfield orientation [roll, pitch, yaw].
	size (List[float]): Size of the heightfield [width, length].
	max_height (float): Maximum height of the heightfield in meters.
	min_height (float): Height in the negative direction of the z axis in meters.
	image_width (int): Width of the heightfield image.
	img_height (int): Height of the heightfield image.
	smooth (float): Smoothing scale for Perlin noise.
	perlin_octaves (int): Number of octaves for Perlin noise. Higher values add more detail.
	perlin_persistence (float): Persistence value for Perlin noise. Controls amplitude of octaves.
	perlin_lacunarity (float): Lacunarity value for Perlin noise. Controls frequency of octaves.
	output_hfield_image (str): Filename for the output heightfield image.
	Octaves, Persistence, and Lacunarity:
	- Octaves: Successive layers of Perlin noise added together for complexity and detail.
	- Persistence: Controls the amplitude decrease of higher octaves (e.g., 0.5 reduces amplitude by half).
	- Lacunarity: Controls the frequency increase of higher octaves (e.g., 2.0 doubles the frequency).
	"""
	# Ensure output directory exists
	output_path = Path(__file__).resolve().parent / f"assets"
	assert output_path.exists(), f"Output path {output_path.absolute().resolve()} does not exist."
	file_path = (output_path / output_hfield_image).with_suffix(".png")
	# Generating height field based on Perlin noise
	terrain_image = np.zeros((img_height, image_width), dtype=np.uint8)
	for y in range(image_width):
	for x in range(image_width):
	noise_value = noise.pnoise2(x / smooth, y / smooth,
	octaves=perlin_octaves,
	persistence=perlin_persistence,
	lacunarity=perlin_lacunarity)
	terrain_image[y, x] = int((noise_value + 1) / 2 * 255)
	cv2.imwrite(str(file_path.resolve()), terrain_image)
	hfield = xml_et.SubElement(asset, "hfield")
	hfield.attrib["name"] = "perlin_hfield"
	hfield.attrib["size"] = list_to_str([size[0] / 2.0, size[1] / 2.0, max_height, min_height])
	hfield.attrib["file"] = str(output_path.resolve())
	geo = xml_et.SubElement(worldbody, "geom")
	geo.attrib["type"] = "hfield"
	geo.attrib["hfield"] = "perlin_hfield"
	geo.attrib["pos"] = list_to_str(position)
	quat_xyzw = Rotation.from_euler("xyz", euler_xyz).as_quat(canonical=True)
	quat_wxyz = np.roll(quat_xyzw, 1)
	geo.attrib["quat"] = list_to_str(quat_wxyz)