Adds ability to set platform height independent of object height for terrain (#2695)

# Description
Allow to set platform height independent of the object height.

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## 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

Credit: @fjenelten-bdai

---------
Signed-off-by: James Tigue <166445701+jtigue-bdai@users.noreply.github.com>
Signed-off-by: Kelly Guo <kellyg@nvidia.com>
Co-authored-by: Kelly Guo <kellyg@nvidia.com>

source/isaaclab/config/extension.toml

 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "0.40.14"
+version = "0.40.15"
 
 # Description
 title = "Isaac Lab framework for Robot Learning"

source/isaaclab/docs/CHANGELOG.rst

 Changelog
 ---------
 
+0.40.15 (2025-07-08)
+~~~~~~~~~~~~~~~~~~~~
+
+Added
+^^^^^
+
+* Added ability to set platform height independent of object height for trimesh terrains.
+
+
 0.40.14 (2025-07-01)
 ~~~~~~~~~~~~~~~~~~~~
 
@@ -37,6 +46,7 @@ Changed
 Added
 ^^^^^
 
+
 * Added unit test for :func:`~isaaclab.utils.math.quat_inv`.
 
 Fixed

source/isaaclab/isaaclab/terrains/trimesh/mesh_terrains.py

@@ -773,6 +773,7 @@ def repeated_objects_terrain(
     # -- common parameters
     num_objects = cp_0.num_objects + int(difficulty * (cp_1.num_objects - cp_0.num_objects))
     height = cp_0.height + difficulty * (cp_1.height - cp_0.height)
+    platform_height = cfg.platform_height if cfg.platform_height >= 0.0 else height
     # -- object specific parameters
     # note: SIM114 requires duplicated logical blocks under a single body.
     if isinstance(cfg, MeshRepeatedBoxesTerrainCfg):
@@ -808,7 +809,7 @@ def repeated_objects_terrain(
     # initialize list of meshes
     meshes_list = list()
     # compute quantities
-    origin = np.asarray((0.5 * cfg.size[0], 0.5 * cfg.size[1], 0.5 * height))
+    origin = np.asarray((0.5 * cfg.size[0], 0.5 * cfg.size[1], 0.5 * platform_height))
     platform_corners = np.asarray([
         [origin[0] - cfg.platform_width / 2, origin[1] - cfg.platform_width / 2],
         [origin[0] + cfg.platform_width / 2, origin[1] + cfg.platform_width / 2],
@@ -851,8 +852,8 @@ def repeated_objects_terrain(
     ground_plane = make_plane(cfg.size, height=0.0, center_zero=False)
     meshes_list.append(ground_plane)
     # generate a platform in the middle
-    dim = (cfg.platform_width, cfg.platform_width, 0.5 * height)
-    pos = (0.5 * cfg.size[0], 0.5 * cfg.size[1], 0.25 * height)
+    dim = (cfg.platform_width, cfg.platform_width, 0.5 * platform_height)
+    pos = (0.5 * cfg.size[0], 0.5 * cfg.size[1], 0.25 * platform_height)
     platform = trimesh.creation.box(dim, trimesh.transformations.translation_matrix(pos))
     meshes_list.append(platform)
 

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

@@ -42,6 +42,10 @@ class MeshPyramidStairsTerrainCfg(SubTerrainBaseCfg):
     """The width of the steps (in m)."""
     platform_width: float = 1.0
     """The width of the square platform at the center of the terrain. Defaults to 1.0."""
+    platform_height: float = -1.0
+    """The height of the platform.  Defaults to -1.0.
+
+    If the value is negative, the height is the same as the object height."""
     holes: bool = False
     """If True, the terrain will have holes in the steps. Defaults to False.