The sampling points generated by flat_patch_sampling are highly unevenly distributed

[DrPengZhe]

I am using flat_patch_sampling to collect obstacle-free points as initial positions for my robots. However, when visualizing these points in yellow, I found that their distribution across the map is extremely uneven—some areas contain a large number of points, while others have very few. This uneven distribution undermines my goal of having robots spawn randomly and uniformly across the terrain. Since I am using only a single sub-terrain, I am not sure what is causing the issue. Below is the code I used to generate the terrain. Any help or insight would be greatly appreciated!

        terrain_cfg = TerrainImporterCfg(
            num_envs=self.num_envs,
            prim_path="/World/defaultGroundPlane",
            terrain_type="generator",
            terrain_generator=TerrainGeneratorCfg(
                seed=0,
                curriculum=False,
                size=(75.0, 75.0),
                border_width=5.0,
                num_rows=1,
                num_cols=1,
                horizontal_scale=0.1,
                vertical_scale=0.1, 
                use_cache=False,
                sub_terrains={
                    "obstacles": HfDiscreteObstaclesTerrainCfg(
                        obstacle_height_mode="fixed",   # The mode to use for the obstacle height:   choice   fixed
                        size=(75.0, 75.0),
                        horizontal_scale=0.1,
                        vertical_scale=0.1,  # 1.0   0.1
                        border_width=0.0,
                        num_obstacles=50,
                        obstacle_width_range=(1.0, 2.0),
                        obstacle_height_range=(10.0, 10.0), 
                        platform_width=0.1, 
                        flat_patch_sampling={
                            "target": FlatPatchSamplingCfg(
                                num_patches=20000,
                                patch_radius=0.8,  
                                max_height_diff=0.)
                        },
                    )
                },
            ),
        )
        terrain: TerrainImporter = terrain_cfg.class_type(terrain_cfg)
        self.valid_positions: torch.Tensor = terrain.flat_patches['target']   # [num_rows, num_cols, num_patches, 3]

[DrPengZhe]

And I also set patch_radius = 0.8, but some sampled points still appear inside obstacles. From the visualization, you can clearly see yellow points located on top of obstacles. I tried adjusting this value to 0.9, 1.0, and so on, but none of these settings solved the issue. Unfortunately, I am unable to inspect the internal implementation of the flat_patch_sampling function to understand how its sampling logic works. This problem has been troubling me for quite a while.