.. _isaac_sim_conventions:


========================
Conventions Reference
========================

This section provides a reference for the units, representations, and coordinate conventions used within |isaac-sim|.

.. _isaac_sim_conventions_default_units:

Default Units
========================

========================  ============================  =====================================================================
Measurement               Units                         Notes
========================  ============================  =====================================================================
Length	                  Meter 
Mass	                  Kilogram 
Time	                  Seconds
Physics Time-Step         Seconds                        Configurable by User. Default is 1/60. 
Force	                  Newton
Frequency                 Hertz
Linear Drive Stiffness    :math:`kg/s^2`
Angular Drive Stiffness   :math:`(kg*m^2)/(s^2*angle)`
Linear Drive Damping      :math:`kg/s`
Angular Drive Damping     :math:`(kg*m^2)/(s*angle)`
Diagonal of Inetria       :math:`(kg*m^2)`
========================  ============================  =====================================================================

.. _isaac_sim_conventions_default_rotation_rep:

Default Rotation Representations
================================

Quaternions
-----------
================  ================
API               Representation  
================  ================
Isaac Sim Core    (QW, QX, QY, QZ)  
USD               (QW, QX, QY, QZ)  
PhysX             (QX, QY, QZ, QW) 
Dynamic Control   (QX, QY, QZ, QW)  
================  ================

Angles
-----------
================  ================
API               Representation  
================  ================
Isaac Sim Core    Radians  
USD               Degrees 
PhysX             Radians 
Dynamic Control   Radians  
================  ================

Matrix Order
-------------
================  ================
API               Representation  
================  ================
Isaac Sim Core    Row Major  
USD               Row Major 
================  ================

World Axes
================================

|isaac-sim| follows the right-handed coordinate conventions.

.. image:: /content/images/isaac_conventions_world_frame.png
    :align: center

========================  ================  ==========================================
Direction                 Axis              Notes
========================  ================  ==========================================
Up  	                  +Z 
Forward                   +X
========================  ================  ==========================================

Default Camera Axes
================================

.. image:: /content/images/isaac_conventions_camera_frame.png
    :align: center

========================  ================  ==========================================
Direction                 Axis              Notes
========================  ================  ==========================================
Up  	                  +Y 
Forward                   -Z
========================  ================  ==========================================

.. note:: **Isaac Sim to ROS Conversion**: To convert from Isaac Sim Camera Coordinates to ROS Camera Coordinates, rotate 180 degrees about the X-Axis.


Image Frames (Synthetic Data)
================================

========================  ================  
Coordinate                Corner          
========================  ================
(0,0)  	                  Top Left
========================  ================