Tests material binding inside stage in memory test (#4347)

# Description

Previously the stage in memory test did not check if material binding
worked correctly. During my debugging, I saw that the
`bind_visual_material` command was failing. This MR adds a fix for it
and makes the test check for mateiral binding as well.

Requires merging: #4337

## Type of change

- Bug fix (non-breaking change which fixes an issue)

## Checklist

- [x] I have read and understood the [contribution
guidelines](https://isaac-sim.github.io/IsaacLab/main/source/refs/contributing.html)
- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [ ] 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

Author: Mayankm96

source/isaaclab/isaaclab/sim/simulation_context.py

@@ -27,7 +27,7 @@
 from isaacsim.core.api.simulation_context import SimulationContext as _SimulationContext
 from isaacsim.core.simulation_manager import SimulationManager
 from isaacsim.core.utils.viewports import set_camera_view
-from pxr import Gf, PhysxSchema, Sdf, Usd, UsdPhysics
+from pxr import Gf, PhysxSchema, Sdf, Usd, UsdPhysics, UsdUtils
 
 import isaaclab.sim as sim_utils
 from isaaclab.utils.logger import configure_logging
@@ -146,6 +146,11 @@ def __init__(self, cfg: SimulationCfg | None = None):
             self._initial_stage = sim_utils.create_new_stage_in_memory()
         else:
             self._initial_stage = omni.usd.get_context().get_stage()
+        # cache stage if it is not already cached
+        stage_cache = UsdUtils.StageCache.Get()
+        stage_id = stage_cache.GetId(self._initial_stage).ToLongInt()
+        if stage_id < 0:
+            stage_cache.Insert(self._initial_stage)
 
         # acquire settings interface
         self.carb_settings = carb.settings.get_settings()

source/isaaclab/isaaclab/sim/utils/prims.py

@@ -206,6 +206,8 @@ def delete_prim(prim_path: str | Sequence[str], stage: Usd.Stage | None = None)
         prim_path = [prim_path]
     # get stage handle
     stage = get_current_stage() if stage is None else stage
+    # FIXME: We should not need to cache the stage here. It should
+    # happen at the creation of the stage.
     # the prim command looks for the stage ID in the stage cache
     # so we need to ensure the stage is cached
     stage_cache = UsdUtils.StageCache.Get()

source/isaaclab/test/sim/test_simulation_stage_in_memory.py

@@ -71,12 +71,35 @@ def test_stage_in_memory_with_shapes(sim):
                 sim_utils.ConeCfg(
                     radius=0.3,
                     height=0.6,
+                    visual_material=sim_utils.PreviewSurfaceCfg(diffuse_color=(0.0, 1.0, 0.0)),
+                    physics_material=sim_utils.RigidBodyMaterialCfg(
+                        friction_combine_mode="multiply",
+                        restitution_combine_mode="multiply",
+                        static_friction=1.0,
+                        dynamic_friction=1.0,
+                    ),
                 ),
-                sim_utils.CuboidCfg(
+                sim_utils.MeshCuboidCfg(
                     size=(0.3, 0.3, 0.3),
+                    visual_material=sim_utils.MdlFileCfg(
+                        mdl_path=f"{ISAACLAB_NUCLEUS_DIR}/Materials/TilesMarbleSpiderWhiteBrickBondHoned/TilesMarbleSpiderWhiteBrickBondHoned.mdl",
+                        project_uvw=True,
+                        texture_scale=(0.25, 0.25),
+                    ),
                 ),
                 sim_utils.SphereCfg(
                     radius=0.3,
+                    visual_material=sim_utils.MdlFileCfg(
+                        mdl_path=f"{ISAACLAB_NUCLEUS_DIR}/Materials/TilesMarbleSpiderWhiteBrickBondHoned/TilesMarbleSpiderWhiteBrickBondHoned.mdl",
+                        project_uvw=True,
+                        texture_scale=(0.25, 0.25),
+                    ),
+                    physics_material=sim_utils.RigidBodyMaterialCfg(
+                        friction_combine_mode="multiply",
+                        restitution_combine_mode="multiply",
+                        static_friction=1.0,
+                        dynamic_friction=1.0,
+                    ),
                 ),
             ],
             random_choice=True,