Implementation:CARLA simulator Carla ActorAttribute

Knowledge Sources	CARLA
Domains	Actor System, RPC Serialization
Last Updated	2026-02-15 05:00 GMT

Overview

ActorAttribute and ActorAttributeValue are RPC-serializable classes that represent configurable attributes and their values for CARLA actor blueprints.

Description

Defined in the carla::rpc namespace, this file provides two classes:

ActorAttribute represents a full attribute definition including: a string id, an ActorAttributeType (defaulting to Int), a value string, a list of recommended_values, a flag is_modifiable (default true), and restrict_to_recommended (default false). When compiled in UE4 context, it can be constructed from FActorAttribute or FActorVariation types.

ActorAttributeValue is a lightweight version containing only id, type, and value, used when transmitting the selected attribute values rather than the full definition. It can be constructed from an ActorAttribute and supports UE4 conversion to/from FActorAttribute.

Both classes use MSGPACK_DEFINE_ARRAY for serialization.

Usage

Use ActorAttribute when querying available actor blueprints and their configurable parameters. Use ActorAttributeValue when setting specific attribute values during actor spawning.

Code Reference

Source Location

Repository: CARLA
File: LibCarla/source/carla/rpc/ActorAttribute.h

Signature

namespace carla {
namespace rpc {

  class ActorAttribute {
  public:
    ActorAttribute() = default;

    std::string id;
    ActorAttributeType type = ActorAttributeType::Int;
    std::string value;
    std::vector<std::string> recommended_values;
    bool is_modifiable = true;
    bool restrict_to_recommended = false;

    MSGPACK_DEFINE_ARRAY(id, type, value, recommended_values,
                         is_modifiable, restrict_to_recommended);
  };

  class ActorAttributeValue {
  public:
    ActorAttributeValue() = default;
    ActorAttributeValue(const ActorAttribute &attribute);

    std::string id;
    ActorAttributeType type = ActorAttributeType::Int;
    std::string value;

    MSGPACK_DEFINE_ARRAY(id, type, value);
  };

} // namespace rpc
} // namespace carla

Import

#include "carla/rpc/ActorAttribute.h"

I/O Contract

Field	Type	Default	Description
id	`std::string`	empty	Attribute identifier name
type	`ActorAttributeType`	Int	Data type (Int, Float, String, Bool, etc.)
value	`std::string`	empty	Current value as string
recommended_values	`std::vector<std::string>`	empty	List of suggested/allowed values
is_modifiable	`bool`	true	Whether the attribute can be changed by the user
restrict_to_recommended	`bool`	false	Whether value must be from recommended_values

Usage Examples

#include "carla/rpc/ActorAttribute.h"

// Query blueprint attributes
for (const auto &attr : definition.attributes) {
    if (attr.id == "color" && attr.is_modifiable) {
        // Choose from recommended values
        for (const auto &val : attr.recommended_values) {
            // e.g., "255,0,0"
        }
    }
}

Related Pages

Page Connections

Double-click a node to navigate. Hold to expand connections.

Principle

Implementation

Heuristic

Environment