# Pose and orientation

A **pose** is a position and an orientation together: where the tool is and which way it points. Six numbers:
x, y, z in millimetres and three angles in degrees, `[x, y, z, Rx, Ry, Rz]`, in the frame you name, the WRF
unless you say TRF.

## Position

The tool centre point's coordinates in the frame. For the standard pneumatic gripper the TCP is between the
finger tips; for a selected tool in the API it is the tool's registered point, moved by any offset you set.

## Orientation

Three angles describe how the tool frame is rotated relative to the reference frame. There are many conventions;
PAROL6's software uses **roll, pitch and yaw as rotations about X, Y and Z**, which is what the commander shows
as Rx, Ry, Rz and what the API's `pose()` returns and its motion commands take. The API's `set_tcp_transform()`
takes its angles as intrinsic XYZ rotations, `Rx · Ry · Rz`; its collision shapes take extrinsic XYZ in radians.
When a pose from one program goes into another, check the convention before trusting the numbers.

The same position can be reached with many orientations, and the orientation is what a program usually gets
wrong first: a few degrees off puts a finger into the table. The Python API examples on this site use
`[90, 0, 90]`, the orientation the tool has after homing: horizontal, pointing forward, away from the base. A
tool pointing down at the table has other angles; jog it there and read them.

![The same position with two orientations](https://docs.source-robotics.com/PAROL-docs/1.1/assets/orientations.webp){ width="650" }

## Reading a pose from the robot

Jog to where you want to be and read the pose: the commander's position display, or `rbt.pose()`. That is how
poses are taught. A taught pose contains the tool's transform: taught with one tool, it is wrong for another.

## Rotating about several axes

A rotation about X followed by one about Y is not the same as Y then X, and three angles at once are hard to
predict. Rotate about one axis per command when you can, especially in the tool frame:

```
MoveCartRelTRF(0, 0, 0, 0, 45, 0)
MoveCartRelTRF(0, 0, 0, 0, 0, 45)
```