[Question] Does Terrain Generator support adjusting terrain mesh during training process?

[yufengsjtu]

Does Terrain Generator support adjusting terrain mesh during training process?

Hi, I would like to ask if the terrain generator in Isaac Lab supports adjusting the terrain during the training process? I noticed that the terrain mesh is currently pre-loaded during the preparation phase before training begins. Is it possible to quickly adjust the mesh through warp mesh? Or through other computationally efficient methods?

[RandomOakForest]

Thank you for posting this. Currently, Isaac Lab does not support real-time adjustment of terrain meshes during the training process. A couple of workarounds to consider are:

• Pre-generate variants: Create multiple terrain configurations offline and switch them between episodes.

• Use height fields: Apply runtime height-field modifications via PhysX APIs (outside TerrainGenerator), though this may require custom integration.

[Ashutosh781]

Hello @RandomOakForest, thank you for your tips.

• Use height fields: Apply runtime height-field modifications via PhysX APIs (outside TerrainGenerator), though this may require custom integration.

Could you elaborate more on this part on how to use height fields via PhysX API to adjust the terrain?

[RandomOakForest]

Thanks for following up. I'll move this post to our Discussions section for follow up. Here is a preliminary overview on using height fields via PhysX.

Runtime Height-Field Modifications via PhysX APIs

While Isaac Lab's TerrainGenerator doesn't support real-time mesh adjustments, PhysX provides direct APIs for dynamic height-field modifications that can be integrated into training workflows. Below are key methods with implementation references:

1. modifySamples() API

Purpose: Replace rectangular sub-regions of height-field data at runtime.
Implementation (based on PhysX 5.3.1): ¹²

// Pseudo-code for height-field updates
PxHeightField* hf = ...; // Existing height-field object
PxHeightFieldSample newSamples[] = ...; // New height data

PxHeightFieldDesc subfieldDesc;
subfieldDesc.samples.data = newSamples;
subfieldDesc.nbRows = 10; // Sub-region height
subfieldDesc.nbColumns = 10; // Sub-region width

// Apply modifications
hf->modifySamples(
    startCol, // Starting column index
    startRow, // Starting row index
    subfieldDesc,
    false // shrinkBounds
);

// Update collision shapes
PxShape* hfShape = ...; // Terrain collision shape
hfShape->setGeometry(PxHeightFieldGeometry(hf)); // Force geometry update

Key Notes:

• Requires recomputing collision geometry via setGeometry() after modification ²¹.
• Samples must respect the original height quantization range ¹.

2. Height-Field Regeneration Workflow

For large-scale terrain changes:

1. Regenerate Height Data:

# Isaac Lab: Regenerate subset of terrain  
from isaaclab.terrains.height_field import HfTerrainBaseCfg, pyramid_sloped_terrain  

new_cfg = HfTerrainBaseCfg(  
    size=(20.0, 20.0),  
    slope_range=(0.3, 0.7) # Adjusted parameters  
)  
new_heightfield = pyramid_sloped_terrain(difficulty=0.8, cfg=new_cfg)  

2. Update PhysX Assets:
   • Convert new_heightfield to PhysX PxHeightField format.
   • Apply via modifySamples() or full reinitialization.

3. Performance-Optimized Workflow

Scenario: Frequent small updates (e.g., deformations under robot feet).
Approach:

• Sub-region Focus: Modify only affected tiles (e.g., 10x10 samples).
• GPU Acceleration: Use CUDA kernels for parallel height updates.
• Incremental Bounds Update: Set shrinkBounds=False in modifySamples() to avoid full recomputation ¹.

Summary: PhysX enables efficient height-field updates via modifySamples() and setGeometry(), but requires custom integration outside Isaac Lab's TerrainGenerator. Prioritize small sub-region updates and GPU parallelism for training-compatible performance.

Footnotes

1. https://nvidia-omniverse.github.io/PhysX/physx/5.3.1/_api_build/class_px_height_field.html ↩ ↩² ↩³ ↩⁴

2. https://docs.nvidia.com/gameworks/content/gameworkslibrary/physx/guide/Manual/Geometry.html ↩ ↩²