25. OpenPLX for AGX Dynamics¶

OpenPLX is a high-level modeling language designed to work seamlessly with AGX Dynamics. It provides a structured approach to defining physics simulations, allowing users to create and configure rigid bodies, constraints, motors, friction models, and more in a human-readable format.

By leveraging AGX Dynamics, OpenPLX enables the simulation of complex mechanical systems, vehicles, robotics, and deformable terrains with minimal effort.

This page explains how OpenPLX interacts with AGX Dynamics and provides a structured way to define physics simulations. For a complete overview of OpenPLX Syntax and Bundles, consult the OpenPLX Documentation.

25.1. How OpenPLX Works with AGX Dynamics¶

OpenPLX acts as an interface layer for AGX Dynamics, converting structured OpenPLX definitions into AGX simulation components. When you load an OpenPLX file, it is transformed into an AGX Dynamics simulation tree, allowing for efficient physics-based interactions.

This means:

OpenPLX describes the physics setup and the scene.
The AGX Dynamics engine executes the simulation.
Users can interact with the scene through OpenPLX files.
Python controllers interact by sending or receiving OpenPLX signals.

25.2. Simulating an OpenPLX File in AGX Viewer¶

To simulate an .openplx file with AGX Dynamics, pass it to agxViewer like you would with an .agx file:

agxViewer myModel.openplx

25.3. Importing an AGX File in OpenPLX¶

AGX .agx files contain pre-defined physics models. OpenPLX supports seamless integration of AGX models into simulation systems.

The AGX Model describes the basic physics setup, including rigid bodies, constraints, collision geometries and visuals.
OpenPLX imports the AGX model and augments it with additional components, such as tracks and a drivetrain.
OpenPLX describes the complete simulation scene.
Controller scripts (python/C++) connects the OpenPLX model to the desired control systems.
The AGX Dynamics engine executes the simulation.

25.3.1. Syntax for Importing an AGX File¶

To import an .agx file into OpenPLX, use the following OpenPLX syntax:

import @"model.agx" as AGXModel

Scene is Physics3D.System:
  my_model is AGXModel

The imported AGX model (AGXModel) can now be referenced within OpenPLX.

To load the OpenPLX scene and view the AGX model, use:

agxViewer scene.openplx -p

25.3.2. Viewing an AGX File as an OpenPLX Model¶

You can open an AGX file to find the components you need to reference using the anytoopenplx command:

python -m agxPythonModules.openplx.anytoopenplx model.agx > model_reference.openplx

Use this file to identify signals and components to reference when augmenting your model with additional OpenPLX components.

Note

At the moment, the models generated OpenPLX file will duplicate the content of the agx file, creating a conflict when running the simulation. To accomodate this, change the file extension of the new .openplx file to .txt, or place it outside the root folder of your OpenPLX bundle.

25.4. OpenPLX Tutorials¶

Explore the OpenPLX Tutorials to get started with OpenPLX for AGX Dynamics.

25.5. AGX Annotations¶

Table 25.1 AGX Parameters¶
Annotation	Description	Type
agx_relaxation_time	Directly set the AGX Dampling. Applies to: `Physics3D.Interactions.Mate`	Real
agx_solve_type	Set the AGX Solve type for a constraint. Applies to `Physics3D.Interactions.Mate` Accepted values `"DIRECT" \| "DIRECT_AND_ITERATIVE" \| "ITERATIVE"`	String
agx_friction_solve_type	Sets the AGX Solve type for the fricion model. Applies to `Physics.Interactions.Dissipation.DefaultDissipation` Accepted values `"SPLIT" \| "DIRECT" \| "DIRECT_AND_ITERATIVE" \| "ITERATIVE"`	String
agx_approximate_cone_friction	Enables AGX approximate cone friction.	Bool
agx_terrain_material	Sets an AGX terrain material preset. Applies to `Terrain.TerrainMaterial`	String
agx_actuator_internal_inertia	Sets the internal inertia of the input shaft of a agxPowerLine::RotationalActuator or the internal mass of the input rod of a agxPowerLine::TranslationalActuator. Applies to `DriveTrain.HingeActuator` and `DriveTrain.PrismaticActuator`	Real
agx_observer_frame	Maps a `Physics3D.Charges.MateConnector` to a agx::ObserverFrame. Applies to `Physics3D.Charges.MateConnector`	Bool
agx_debug_render_frame	Renders the axes of a `Physics3D.Charges.MateConnector`, also maps it to a agx::ObserverFrame. Applies to `Physics3D.Charges.MateConnector`	Bool

25.6. AGX Track Annotations¶

The following annotations can be applied to a Vehicles.Tracks.System to set AGX internal track properties.

Table 25.2 AGX Track Annotations¶
Annotation	Description	Type
agx_track_node_wheel_overlap	setTransformNodesToWheelsOverlap	Real
agx_track_on_initialize_merge_nodes_to_wheels	setEnableOnInitializeMergeNodesToWheels	Bool
agx_track_on_initialize_transform_nodes_to_wheels	setEnableOnInitializeTransformNodesToWheels	Bool
agx_track_hinge_range_lower, agx_track_hinge_range_upper	setHingeRangeRange	Real
agx_track_hinge_compliance	setHingeCompliance	Real
agx_track_hinge_relaxation_time	setHingeDamping	Real
agx_track_stabilizing_friction_parameter	setStabilizingHingeFrictionParameter	Real
agx_track_min_stabilizing_normal_force	setMinStabilizingHingeNormalForce	Real
agx_track_node_wheel_merge_threshold	setNodesToWheelsMergeThreshold	Real
agx_track_node_wheel_split_threshold	setNodesToWheelsSplitThreshold	Real
agx_track_num_nodes_in_average_direction	setNumNodesIncludedInAverageDirection	Int
agx_set_enable_merge	setEnableMerge	Bool
agx_set_contact_reduction	setContactReduction Accepts: `"NONE" \| "MINIMAL" \| "MODERATE" \| "AGGRESSIVE"`	String
agx_set_enable_lock_to_reach_merge_condition	setEnableLockToReachMergeCondition	Bool
agx_set_lock_to_reach_merge_condition_compliance	setLockToReachMergeConditionCompliance	Real
agx_set_lock_to_reach_merge_condition_relaxation_time	setLockToReachMergeConditionDamping	Real
agx_set_num_nodes_per_merge_segment	setNumNodesPerMergeSegment	Int

25.7. AGX Plugin Annotations¶

When importing a .agx file there are a few annotations that change the import behavior.

Table 25.3 AGX Plugin Annotations¶
Annotation	Description	Type
discard_rigid_body_positions	Discards all position information for rigid bodies if set to `true`, allowing SNAP to reposition them.	Bool
regenerate_shape_uuids	Setting this to `true` will create new UUIDs for all AGX shapes. This is useful when importing the same `.agx` file twice.	Bool
material_naming_rule	Controls how imported materials will be named. This can be necessary to avoid collisions since materials are always put in a global scope. Accepted values `"UUID"` sets the material `unique_name` to the AGX UUID. `"OPENPLX_NAME"` sets the material `unique_name` to the OpenPLX name. `"AGX_NAME"` (default) sets the material `unique_name` to the AGX name. If UUIDs are not unique, try `"OPENPLX_NAME"` together with a namespace to generate unique names.	String