You might be thinking this isn't a very precise way of selecting a point, and you are correct, but in many cases it is sufficient that the point selected is guaranteed to be on that edge or face. It is this point's coordinates that get used in the Placement dialog when the Selected points button is clicked. When you select an edge or face the entire edge or face is selected, but FreeCAD also remembers which point on that face or edge the mouse pointer was hovering over when that edge or face was selected. A point can be a vertex, but it can also be any point along an edge or on a face. Selected points button is used to populate the coordinates in the Center coordinates spinboxes and (when 2 or 3 points are selected) additionally to create a custom (user-defined) axis of rotation in the Rotation section. getParentGeoFeatureGroup ()) # return the GeoFeatureGroup, ex: Body or a Part. getGlobalPlacement ()) # return the GlobalPlacement print ( sel. To obtain the Part Placement use this code: PS: since version 0.17 introduce new object Part, this object have his placement, and the Placement object created in the Part object is incremented with the Part Placement. Enabling this checkbox is also useful when using the Selected points button as it can sometimes prevent undesired placement changes. Subsequent entries do change the orientation/location, but are applied from the object's current position. Ticking this box resets the dialogue input fields to zero, but does not change the object's orientation or location. The Apply incremental changes to object placement tick box is useful when translations/rotations are to be made relative the object's current position/attitude, rather than to the original position/attitude. In another example, placing a value in the Axial spinbox and clicking the Apply axial button in the Translation section translates (moves) the object along the axis defined in the Rotation section. For example, clicking the Selected points button in the Center section with 2 points selected in the 3d view results in not only populating the Center coordinate spinboxes with the coordinates of the midpoint between those 2 selected points, but it also creates a custom axis along the line defined by those 2 selected points in the Rotation section. The Rotation section adjusts the rotational angle(s) and the method of specifying those angles.īut while the elements within each section generally apply to the purpose of that section there are also some elements in one section that can affect elements in another section.The Center section adjusts the rotational axis to one that does not pass through the object's reference point.The Translation section adjusts the object's location in space.It is also used when we need to create a sketch on a "non standard" plane or change a sketch's orientation to a new plane. It is used to precisely rotate/translate objects. The Placement Dialog is invoked from the Edit menu. The property editor calls this value Position and the Placement task panel calls it Translation. Note that in scripts, Placement.Base is used to denote the Position component of a placement. Position = (x,y,z) is a Vector describing the point from which the object's geometry will be calculated (in effect, a "local origin" for the object). For example, in the y=x case (0.71,0.71,0) the value contained in the Axial spinbox gets applied in equal measure to the X and Y directions, but no movement happens in the Z direction. (One way to envision axial motion is to think of an airplane with a propeller spinning on its nose - the propeller spins about an axis of rotation while the plane moves along that same axis.) The values in the vector can be thought of as the relative amount of motion that will be applied in that direction. Note that it is also possible to translate (move) an object along this axis of rotation (axial motion) by entering the distance to move in the Axial: 0.0mm spinbox and clicking Apply axial. Entered as degrees, but stored internally as radians.Īxis = (ax,ay,az) is a vector describing an axis of rotation (See Note about axis of rotation). The first form of Placement fixes an object's location in space with a Position, and describes its orientation as a single rotation about an axis.Īngle = r is a scalar indicating the amount of rotation of the object about Axis. Similarly, if a rotation axis of (1,1,1) is specified, it may be normalized when stored in the quaternion and appear as (0.58, 0.58, 0.58) when browsing the object later. While there are several forms to specify a rotation, for instance with a rotation center, this is only used to affect the rotation computation and is not stored for later operations. The placement is stored internally as a position and a rotation (rotation axis and angle transformed into a quaternion).
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