Allows for custom `TerrainGenerator` without modifications of the `TerrainImporter` (#2487)

# Description

Currently, the `TerrainGenerator` class is hardcoded in the
`TerrainImporter`. This class resolves this issue and allows for custom
implementations.

## Type of change

- New feature (non-breaking change which adds functionality)

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

---------
Signed-off-by: Kelly Guo <kellyg@nvidia.com>
Signed-off-by: Kelly Guo <kellyguo123@hotmail.com>
Co-authored-by: Mayank Mittal <12863862+Mayankm96@users.noreply.github.com>
Co-authored-by: Kelly Guo <kellyg@nvidia.com>
Co-authored-by: Kelly Guo <kellyguo123@hotmail.com>

source/isaaclab/config/extension.toml

 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "0.40.3"
+version = "0.40.4"
 
 # Description
 title = "Isaac Lab framework for Robot Learning"

source/isaaclab/docs/CHANGELOG.rst

 Changelog
 ---------
 
+0.40.4 (2025-06-03)
+~~~~~~~~~~~~~~~~~~~
+
+Changed
+^^^^^^^
+
+* Removes the hardcoding to :class:`~isaaclab.terrains.terrain_generator.TerrainGenerator` in
+  :class:`~isaaclab.terrains.terrain_generator.TerrainImporter` and instead the ``class_type`` is used which is
+  passed in the ``TerrainGeneratorCfg``.
+
+
 0.40.3 (2025-03-20)
 ~~~~~~~~~~~~~~~~~~~
 

source/isaaclab/isaaclab/terrains/__init__.py

@@ -24,10 +24,10 @@ There are two main components in this package:
   * :meth:`TerrainImporter.import_usd`: spawn a prim as reference to input USD file.
 
 """
-
 from .height_field import *  # noqa: F401, F403
+from .sub_terrain_cfg import FlatPatchSamplingCfg, SubTerrainBaseCfg
 from .terrain_generator import TerrainGenerator
-from .terrain_generator_cfg import FlatPatchSamplingCfg, SubTerrainBaseCfg, TerrainGeneratorCfg
+from .terrain_generator_cfg import TerrainGeneratorCfg
 from .terrain_importer import TerrainImporter
 from .terrain_importer_cfg import TerrainImporterCfg
 from .trimesh import *  # noqa: F401, F403

source/isaaclab/isaaclab/terrains/height_field/hf_terrains_cfg.py

@@ -12,7 +12,7 @@ from dataclasses import MISSING
 
 from isaaclab.utils import configclass
 
-from ..terrain_generator_cfg import SubTerrainBaseCfg
+from ..sub_terrain_cfg import SubTerrainBaseCfg
 from . import hf_terrains
 
 

source/isaaclab/isaaclab/terrains/sub_terrain_cfg.py

+# Copyright (c) 2022-2025, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+
+from __future__ import annotations
+
+import numpy as np
+import trimesh
+from collections.abc import Callable
+from dataclasses import MISSING
+
+from isaaclab.utils import configclass
+
+
+@configclass
+class FlatPatchSamplingCfg:
+    """Configuration for sampling flat patches on the sub-terrain.
+
+    For a given sub-terrain, this configuration specifies how to sample flat patches on the terrain.
+    The sampled flat patches can be used for spawning robots, targets, etc.
+
+    Please check the function :meth:`~isaaclab.terrains.utils.find_flat_patches` for more details.
+    """
+
+    num_patches: int = MISSING
+    """Number of patches to sample."""
+
+    patch_radius: float | list[float] = MISSING
+    """Radius of the patches.
+
+    A list of radii can be provided to check for patches of different sizes. This is useful to deal with
+    cases where the terrain may have holes or obstacles in some areas.
+    """
+
+    x_range: tuple[float, float] = (-1e6, 1e6)
+    """The range of x-coordinates to sample from. Defaults to (-1e6, 1e6).
+
+    This range is internally clamped to the size of the terrain mesh.
+    """
+
+    y_range: tuple[float, float] = (-1e6, 1e6)
+    """The range of y-coordinates to sample from. Defaults to (-1e6, 1e6).
+
+    This range is internally clamped to the size of the terrain mesh.
+    """
+
+    z_range: tuple[float, float] = (-1e6, 1e6)
+    """Allowed range of z-coordinates for the sampled patch. Defaults to (-1e6, 1e6)."""
+
+    max_height_diff: float = MISSING
+    """Maximum allowed height difference between the highest and lowest points on the patch."""
+
+
+@configclass
+class SubTerrainBaseCfg:
+    """Base class for terrain configurations.
+
+    All the sub-terrain configurations must inherit from this class.
+
+    The :attr:`size` attribute is the size of the generated sub-terrain. Based on this, the terrain must
+    extend from :math:`(0, 0)` to :math:`(size[0], size[1])`.
+    """
+
+    function: Callable[[float, SubTerrainBaseCfg], tuple[list[trimesh.Trimesh], np.ndarray]] = MISSING
+    """Function to generate the terrain.
+
+    This function must take as input the terrain difficulty and the configuration parameters and
+    return a tuple with a list of ``trimesh`` mesh objects and the terrain origin.
+    """
+
+    proportion: float = 1.0
+    """Proportion of the terrain to generate. Defaults to 1.0.
+
+    This is used to generate a mix of terrains. The proportion corresponds to the probability of sampling
+    the particular terrain. For example, if there are two terrains, A and B, with proportions 0.3 and 0.7,
+    respectively, then the probability of sampling terrain A is 0.3 and the probability of sampling terrain B
+    is 0.7.
+    """
+
+    size: tuple[float, float] = (10.0, 10.0)
+    """The width (along x) and length (along y) of the terrain (in m). Defaults to (10.0, 10.0).
+
+    In case the :class:`~isaaclab.terrains.TerrainImporterCfg` is used, this parameter gets overridden by
+    :attr:`isaaclab.scene.TerrainImporterCfg.size` attribute.
+    """
+
+    flat_patch_sampling: dict[str, FlatPatchSamplingCfg] | None = None
+    """Dictionary of configurations for sampling flat patches on the sub-terrain. Defaults to None,
+    in which case no flat patch sampling is performed.
+
+    The keys correspond to the name of the flat patch sampling configuration and the values are the
+    corresponding configurations.
+    """

source/isaaclab/isaaclab/terrains/terrain_generator.py

@@ -8,10 +8,13 @@
 #
 # SPDX-License-Identifier: BSD-3-Clause
 
+from __future__ import annotations
+
 import numpy as np
 import os
 import torch
 import trimesh
+from typing import TYPE_CHECKING
 
 import omni.log
 
@@ -20,11 +23,13 @@ from isaaclab.utils.io import dump_yaml
 from isaaclab.utils.timer import Timer
 from isaaclab.utils.warp import convert_to_warp_mesh
 
-from .height_field import HfTerrainBaseCfg
-from .terrain_generator_cfg import FlatPatchSamplingCfg, SubTerrainBaseCfg, TerrainGeneratorCfg
 from .trimesh.utils import make_border
 from .utils import color_meshes_by_height, find_flat_patches
 
+if TYPE_CHECKING:
+    from .sub_terrain_cfg import FlatPatchSamplingCfg, SubTerrainBaseCfg
+    from .terrain_generator_cfg import TerrainGeneratorCfg
+
 
 class TerrainGenerator:
     r"""Terrain generator to handle different terrain generation functions.
@@ -113,6 +118,8 @@ class TerrainGenerator:
         self.device = device
 
         # set common values to all sub-terrains config
+        from .height_field import HfTerrainBaseCfg  # prevent circular import
+
         for sub_cfg in self.cfg.sub_terrains.values():
             # size of all terrains
             sub_cfg.size = self.cfg.size

source/isaaclab/isaaclab/terrains/terrain_generator_cfg.py

@@ -19,100 +19,25 @@ inherit from ``isaaclab.terrains.terrains_cfg.TerrainConfig`` and define the fol
 
 from __future__ import annotations
 
-import numpy as np
-import trimesh
-from collections.abc import Callable
 from dataclasses import MISSING
 from typing import Literal
 
 from isaaclab.utils import configclass
 
-
-@configclass
-class FlatPatchSamplingCfg:
-    """Configuration for sampling flat patches on the sub-terrain.
-
-    For a given sub-terrain, this configuration specifies how to sample flat patches on the terrain.
-    The sampled flat patches can be used for spawning robots, targets, etc.
-
-    Please check the function :meth:`~isaaclab.terrains.utils.find_flat_patches` for more details.
-    """
-
-    num_patches: int = MISSING
-    """Number of patches to sample."""
-
-    patch_radius: float | list[float] = MISSING
-    """Radius of the patches.
-
-    A list of radii can be provided to check for patches of different sizes. This is useful to deal with
-    cases where the terrain may have holes or obstacles in some areas.
-    """
-
-    x_range: tuple[float, float] = (-1e6, 1e6)
-    """The range of x-coordinates to sample from. Defaults to (-1e6, 1e6).
-
-    This range is internally clamped to the size of the terrain mesh.
-    """
-
-    y_range: tuple[float, float] = (-1e6, 1e6)
-    """The range of y-coordinates to sample from. Defaults to (-1e6, 1e6).
-
-    This range is internally clamped to the size of the terrain mesh.
-    """
-
-    z_range: tuple[float, float] = (-1e6, 1e6)
-    """Allowed range of z-coordinates for the sampled patch. Defaults to (-1e6, 1e6)."""
-
-    max_height_diff: float = MISSING
-    """Maximum allowed height difference between the highest and lowest points on the patch."""
+from .sub_terrain_cfg import SubTerrainBaseCfg
+from .terrain_generator import TerrainGenerator
 
 
 @configclass
-class SubTerrainBaseCfg:
-    """Base class for terrain configurations.
-
-    All the sub-terrain configurations must inherit from this class.
-
-    The :attr:`size` attribute is the size of the generated sub-terrain. Based on this, the terrain must
-    extend from :math:`(0, 0)` to :math:`(size[0], size[1])`.
-    """
-
-    function: Callable[[float, SubTerrainBaseCfg], tuple[list[trimesh.Trimesh], np.ndarray]] = MISSING
-    """Function to generate the terrain.
-
-    This function must take as input the terrain difficulty and the configuration parameters and
-    return a tuple with a list of ``trimesh`` mesh objects and the terrain origin.
-    """
-
-    proportion: float = 1.0
-    """Proportion of the terrain to generate. Defaults to 1.0.
-
-    This is used to generate a mix of terrains. The proportion corresponds to the probability of sampling
-    the particular terrain. For example, if there are two terrains, A and B, with proportions 0.3 and 0.7,
-    respectively, then the probability of sampling terrain A is 0.3 and the probability of sampling terrain B
-    is 0.7.
-    """
-
-    size: tuple[float, float] = (10.0, 10.0)
-    """The width (along x) and length (along y) of the terrain (in m). Defaults to (10.0, 10.0).
-
-    In case the :class:`~isaaclab.terrains.TerrainImporterCfg` is used, this parameter gets overridden by
-    :attr:`isaaclab.scene.TerrainImporterCfg.size` attribute.
-    """
+class TerrainGeneratorCfg:
+    """Configuration for the terrain generator."""
 
-    flat_patch_sampling: dict[str, FlatPatchSamplingCfg] | None = None
-    """Dictionary of configurations for sampling flat patches on the sub-terrain. Defaults to None,
-    in which case no flat patch sampling is performed.
+    class_type: type = TerrainGenerator
+    """The class to use for the terrain generator.
 
-    The keys correspond to the name of the flat patch sampling configuration and the values are the
-    corresponding configurations.
+    Defaults to :class:`isaaclab.terrains.terrain_generator.TerrainGenerator`.
     """
 
-
-@configclass
-class TerrainGeneratorCfg:
-    """Configuration for the terrain generator."""
-
     seed: int | None = None
     """The seed for the random number generator. Defaults to None, in which case the seed from the
     current NumPy's random state is used.

source/isaaclab/isaaclab/terrains/terrain_importer.py

@@ -21,7 +21,6 @@ import isaaclab.sim as sim_utils
 from isaaclab.markers import VisualizationMarkers
 from isaaclab.markers.config import FRAME_MARKER_CFG
 
-from .terrain_generator import TerrainGenerator
 from .utils import create_prim_from_mesh
 
 if TYPE_CHECKING:
@@ -89,7 +88,9 @@ class TerrainImporter:
             if self.cfg.terrain_generator is None:
                 raise ValueError("Input terrain type is 'generator' but no value provided for 'terrain_generator'.")
             # generate the terrain
-            terrain_generator = TerrainGenerator(cfg=self.cfg.terrain_generator, device=self.device)
+            terrain_generator = self.cfg.terrain_generator.class_type(
+                cfg=self.cfg.terrain_generator, device=self.device
+            )
             self.import_mesh("terrain", terrain_generator.terrain_mesh)
             # configure the terrain origins based on the terrain generator
             self.configure_env_origins(terrain_generator.terrain_origins)

source/isaaclab/isaaclab/terrains/trimesh/mesh_terrains_cfg.py

@@ -15,7 +15,7 @@ import isaaclab.terrains.trimesh.mesh_terrains as mesh_terrains
 import isaaclab.terrains.trimesh.utils as mesh_utils_terrains
 from isaaclab.utils import configclass
 
-from ..terrain_generator_cfg import SubTerrainBaseCfg
+from ..sub_terrain_cfg import SubTerrainBaseCfg
 
 """
 Different trimesh terrain configurations.