From FreeCAD Documentation

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**Projection**: specifies the direction of the projection as a vector. For example, (0,0,1) is a projection looking through the Z axis, which would be projected on the XY plane; (1,0,0) is a projection looking through the X axis, which would be projected on the YZ plane; (0,1,0) is a projection looking through the Y axis, which would be projected on the XZ plane. The values can also be negative, in which case the direction of projection is inverted.
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**Projection Mode**: it can be "Solid", "Individual Faces", "Cutlines", and "Cutfaces".
- The default projection is "Solid", which projects the entire selected shape.
- If only some faces of the base object are selected, the "Individual Faces" mode will project only those faces.
- If the selected object is an Arch SectionPlane, the "Cutlines" mode will project only the edges being cut by the section plane.
- If the selected object is an Arch SectionPlane, the "Cutfaces" mode will display the cut areas of solids as faces.

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**In Place**: if it is True, together with "Cutlines" or "Cutfaces" modes, the resulting projection will appear co-planar with the Arch SectionPlane. introduced in version 0.17
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**HiddenLines**: if it is True it will show the hidden lines of the projection.
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**Tessellation**: if it is True it will perform tessellation of ellipses and splines, that is, it will represent curves with very fine line segments.

*Note:* this may be computationally intensive if DATA**Segment Length** is very small.

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**Segment Length**: specifies the size in millimeters of linear segments if DATA**Tessellation** is True.

*Note:* set a larger value first, and then change it to a smaller value to get better resolution.

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**Visible Only**: if it is True the projection will be recomputed only if it is visible.