fix terrains, change slope_threshold in every subterrain for correct terrain generation.

source/robot_lab/robot_lab/tasks/go2/mdp/terrains.py

@@ -3,16 +3,40 @@ from __future__ import annotations
 import numpy as np
 
 import isaaclab.terrains as terrain_gen
+from isaaclab.terrains.terrain_generator import TerrainGenerator
 from isaaclab.utils import configclass
 from isaaclab.terrains.height_field import hf_terrains
 from isaaclab.terrains.height_field.utils import height_field_to_mesh
 
 
+class PerSubTerrainSlopeThresholdGenerator(TerrainGenerator):
+    """Terrain generator that lets each height-field sub-terrain override slope_threshold."""
+
+    def _get_terrain_mesh(self, difficulty, cfg):
+        override = getattr(cfg, "slope_threshold_override", None)
+        if override is None:
+            return super()._get_terrain_mesh(difficulty, cfg)
+
+        original_slope_threshold = getattr(cfg, "slope_threshold", None)
+        cfg.slope_threshold = override
+        try:
+            return super()._get_terrain_mesh(difficulty, cfg)
+        finally:
+            cfg.slope_threshold = original_slope_threshold
+
+
+def with_slope_threshold(sub_terrain_cfg, slope_threshold: float | None):
+    """Attach a per-sub-terrain slope-threshold override to a terrain config."""
+    sub_terrain_cfg.slope_threshold_override = slope_threshold
+    return sub_terrain_cfg
+
+
 # -----------------------------------------------------------------------------
 # Default RobotLab terrain setup
 # -----------------------------------------------------------------------------
 
 DEFAULT_TERRAIN_CFG = terrain_gen.TerrainGeneratorCfg(
+    class_type=PerSubTerrainSlopeThresholdGenerator,
     size=(8.0, 8.0),
     border_width=25.0,
     num_rows=10,
@@ -107,50 +131,72 @@ class RoughSlopeTerrainCfg(terrain_gen.HfPyramidSlopedTerrainCfg):
 
 
 TERRAIN_CFG = terrain_gen.TerrainGeneratorCfg(
+    class_type=PerSubTerrainSlopeThresholdGenerator,
     size=(8.0, 8.0),
     border_width=25.0,
     num_rows=10,
     num_cols=20,
     horizontal_scale=0.1,
     vertical_scale=0.005,
-    slope_threshold=2.0,
+    # slope correction = 0.75 ~ 36.9 degrees by default, 
+    # but recommended to set for each terrain type separately using with_slope_threshold
+    slope_threshold=0.75,  
     use_cache=False,
     sub_terrains={
-        "wave": WaveTerrainCfg(
+        "wave": with_slope_threshold(
+            WaveTerrainCfg(
                 proportion=0.05,
                 border_width=0.5,
             ),
-        "slope_up": terrain_gen.HfInvertedPyramidSlopedTerrainCfg(
+            10.0, # effectively disable slope correction for wave terrain
+        ),
+        "slope_up": with_slope_threshold(
+            terrain_gen.HfInvertedPyramidSlopedTerrainCfg(
                 proportion=0.10,
                 slope_range=(0.1, 0.568),
                 platform_width=3.0,
                 border_width=0.5,
             ),
-        "slope_down": terrain_gen.HfPyramidSlopedTerrainCfg(
+            10.0, # effectively disable slope correction for slope_up terrain
+        ),
+        "slope_down": with_slope_threshold(
+            terrain_gen.HfPyramidSlopedTerrainCfg(
                 proportion=0.10,
                 slope_range=(0.1, 0.568),
                 platform_width=3.0,
                 border_width=0.5,
             ),
-        "rough_slope": RoughSlopeTerrainCfg(
+            10.0, # effectively disable slope correction for slope_down terrain
+        ),
+        "rough_slope": with_slope_threshold(
+            RoughSlopeTerrainCfg(
                 proportion=0.05,
                 border_width=0.5,
             ),
-        "stairs_up": terrain_gen.HfInvertedPyramidStairsTerrainCfg(
+            10.0, # effectively disable slope correction for rough_slope terrain
+        ),
+        "stairs_up": with_slope_threshold(
+            terrain_gen.HfInvertedPyramidStairsTerrainCfg(
                 proportion=0.25,
                 step_height_range=(0.05, 0.257),
                 step_width=0.31,
                 platform_width=3.0,
                 border_width=0.5,
             ),
-        "stairs_down": terrain_gen.HfPyramidStairsTerrainCfg(
+            0.25, # enable slope correction for rough_slope terrain by 14.0 degrees, which is recommended for stairs terrain
+        ),
+        "stairs_down": with_slope_threshold(
+            terrain_gen.HfPyramidStairsTerrainCfg(
                 proportion=0.10,
                 step_height_range=(0.05, 0.257),
                 step_width=0.31,
                 platform_width=3.0,
                 border_width=0.5,
             ),
-        "obstacles": terrain_gen.HfDiscreteObstaclesTerrainCfg(
+            0.25, # enable slope correction for rough_slope terrain by 14.0 degrees, which is recommended for stairs terrain
+        ),
+        "obstacles": with_slope_threshold(
+            terrain_gen.HfDiscreteObstaclesTerrainCfg(
                 proportion=0.20,
                 obstacle_width_range=(1.0, 2.0),
                 obstacle_height_range=(0.05, 0.275),
@@ -158,7 +204,10 @@ TERRAIN_CFG = terrain_gen.TerrainGeneratorCfg(
                 platform_width=3.0,
                 border_width=0.5,
             ),
-        "stepping_stones": terrain_gen.HfSteppingStonesTerrainCfg(
+            0.25, # enable slope correction for rough_slope terrain by 14.0 degrees
+        ),
+        "stepping_stones": with_slope_threshold(
+            terrain_gen.HfSteppingStonesTerrainCfg(
                 proportion=0.0,
                 stone_height_max=0.0,
                 stone_width_range=(0.075, 1.575),
@@ -167,6 +216,8 @@ TERRAIN_CFG = terrain_gen.TerrainGeneratorCfg(
                 platform_width=4.0,
                 border_width=0.5,
             ),
+            0.25, # enable slope correction for rough_slope terrain by 14.0 degrees
+        ),
         "gap": terrain_gen.MeshGapTerrainCfg(
             proportion=0.0,
             gap_width_range=(0.0, 0.9),