Simulation Assets

Simulation Assets#

Simulation assets in EmbodiChain are configured using Python dataclasses. This approach provides a structured and type-safe way to define properties for physics, materials and objects in the simulation environment.

Visual Materials#

Configuration#

The VisualMaterialCfg class defines the visual appearance of objects using Physically Based Rendering (PBR) properties.

Parameter	Type	Default	Description
`uid`	`str`	`"default_mat"`	Unique identifier for the material.
`base_color`	`list`	`[0.5, 0.5, 0.5, 1.0]`	Base color/diffuse color (RGBA).
`metallic`	`float`	`0.0`	Metallic factor (0.0 = dielectric, 1.0 = metallic).
`roughness`	`float`	`0.5`	Surface roughness (0.0 = smooth, 1.0 = rough).
`emissive`	`list`	`[0.0, 0.0, 0.0]`	Emissive color (RGB).
`emissive_intensity`	`float`	`1.0`	Emissive intensity multiplier.
`base_color_texture`	`str`	`None`	Path to base color texture map.
`metallic_texture`	`str`	`None`	Path to metallic map.
`roughness_texture`	`str`	`None`	Path to roughness map.
`normal_texture`	`str`	`None`	Path to normal map.
`ao_texture`	`str`	`None`	Path to ambient occlusion map.
`ior`	`float`	`1.5`	Index of refraction for ray tracing materials.

Visual Material and Visual Material Instance#

A visual material is defined using the VisualMaterialCfg class. It is actually a material template that can be used to create multiple instances with different parameters.

A visual material instance is created from a visual material using the method create_instance(). User can set different properties for each instance. For details API usage, please refer to the VisualMaterialInst documentation.

For batch simualtion scenarios, when user set a material to a object (eg, a rigid object with num_envs instances), the material instance will be created for each simulation instance automatically.

Code#

# Create a visual material with base color white and low roughness.
mat: VisualMaterial = sim.create_visual_material(
    cfg=VisualMaterialCfg(
        base_color=[1.0, 1.0, 1.0, 1.0],
        roughness=0.05,
    )
)

# Set the material to a rigid object.
object: RigidObject
object.set_visual_material(mat)

# Get all material instances created for this object in the simulation. If `num_envs` is N, there will be N instances.
mat_inst: List[VisualMaterialInst] = object.get_visual_material_inst()

# We can then modify the properties of each material instance separately.
mat_inst[0].set_base_color([1.0, 0.0, 0.0, 1.0])  

Objects#

All objects inherit from ObjectBaseCfg, which provides common properties.

Base Properties

Parameter	Type	Default	Description
`uid`	`str`	`None`	Unique identifier.
`init_pos`	`tuple`	`(0.0, 0.0, 0.0)`	Position of the root in simulation world frame.
`init_rot`	`tuple`	`(0.0, 0.0, 0.0)`	Euler angles (in degrees) of the root.
`init_local_pose`	`np.ndarray`	`None`	4x4 transformation matrix (overrides `init_pos` and `init_rot`).

Rigid Object#

Configured via RigidObjectCfg.

Parameter	Type	Default	Description
`shape`	`ShapeCfg`	`ShapeCfg()`	Shape configuration (e.g., Mesh, Box).
`attrs`	`RigidBodyAttributesCfg`	`RigidBodyAttributesCfg()`	Physical attributes.
`body_type`	`Literal`	`"dynamic"`	“dynamic”, “kinematic”, or “static”.
`max_convex_hull_num`	`int`	`1`	Max convex hulls for decomposition (CoACD).
`body_scale`	`tuple`	`(1.0, 1.0, 1.0)`	Scale of the rigid body.

Rigid Body Attributes#

The RigidBodyAttributesCfg class defines physical properties for rigid bodies.

Parameter	Type	Default	Description
`mass`	`float`	`1.0`	Mass in kg. Set to 0 to use density.
`density`	`float`	`1000.0`	Density in kg/m^3.
`angular_damping`	`float`	`0.7`	Angular damping coefficient.
`linear_damping`	`float`	`0.7`	Linear damping coefficient.
`max_depenetration_velocity`	`float`	`10.0`	Maximum depenetration velocity.
`sleep_threshold`	`float`	`0.001`	Threshold below which the body can go to sleep.
`enable_ccd`	`bool`	`False`	Enable continuous collision detection.
`contact_offset`	`float`	`0.002`	Contact offset for collision detection.
`rest_offset`	`float`	`0.001`	Rest offset for collision detection.
`enable_collision`	`bool`	`True`	Enable collision for the rigid body.
`restitution`	`float`	`0.0`	Restitution (bounciness) coefficient.
`dynamic_friction`	`float`	`0.5`	Dynamic friction coefficient.
`static_friction`	`float`	`0.5`	Static friction coefficient.

For Rigid Object tutorial, please refer to the Create Scene tutorial.

Rigid Object Groups#

RigidObjectGroupCfg allows initializing multiple rigid objects, potentially from a folder.

Lights#

Configured via LightCfg.

Parameter	Type	Default	Description
`light_type`	`Literal`	`"point"`	Type of light (currently only “point”).
`color`	`tuple`	`(1.0, 1.0, 1.0)`	RGB color.
`intensity`	`float`	`50.0`	Intensity in watts/m^2.
`radius`	`float`	`1e2`	Falloff radius.