Enable collision aggregation in IsaacGym environments with humanoid a…

[OAHC2022]

Fixes #108

[tesslerc]

Sorry it took a bit to reach.
This looks good overall, but I think it needs a better way to access which objects are assigned to which env.

See below:

            for env_id in range(self.num_envs):
                env_ptr = self._gym.create_env(self._sim, lower, upper, num_per_row)
                
                # Aggregate bodies helps improve memory when using objects in IsaacGym
                # calculate the max aggregate body and shape counts for the humanoid robot
                max_agg_bodies = self._gym.get_asset_rigid_body_count(humanoid_asset)
                max_agg_shapes = self._gym.get_asset_rigid_shape_count(humanoid_asset)

                # Fetch the scene associated with this env
                scene = self.scene_lib.scenes[env_id]
                for obj in scene.objects:
                    # Iterate over all objects in the scene, obtain the IsaacGym asset and extract info
                    object_asset = self._object_assets[obj.first_instance_id]
                    max_agg_bodies += self._gym.get_asset_rigid_body_count(object_asset)
                    max_agg_shapes += self._gym.get_asset_rigid_shape_count(object_asset)

                # aggregate body and shapes to save memory
                self._gym.begin_aggregate(env_ptr, max_agg_bodies, max_agg_shapes, True)
                self._build_env(env_id, env_ptr, humanoid_asset, visualization_markers)
                self._gym.end_aggregate(env_ptr)
                self._envs.append(env_ptr)
                progress.update(task, advance=1)