## Shapes: Planes |

A plane shape is an infinite plane surface, defined by specifying a point on the plane and the maximum slope angle and direction of the plane.

The slope angle is the angle of elevation of the line of maximum slope, relative to the $xy$-plane of the connection axes; the slope direction is the direction of the line of maximum upwards slope, again relative to the $xy$-plane of the connection axes. For example, if the plane were **fixed** relative to the global coordinate system, then a slope angle of 0° would represent a horizontal plane, whereas a slope angle 90° would represent a vertical plane. Similarly, a slope angle of 30° and a slope direction of 90° indicate that the plane slopes upwards in the positive $y$-direction at 30° to the $xy$-plane of the connection axes.

The *inside* of a plane is on the negative $z$ side (i.e. below, for a fixed or anchored plane) if the slope angle is in the range -90° to +90°, and on the positive $z$ side (i.e. above for a fixed or anchored plane) otherwise.

The remaining plane data, including its position, are common to all geometric shapes and are described under the shape data and drawing topics.