Difference between revisions of "Sketcher CreateEllipseBy3Points"

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[[Image:Sketcher_EllipseExample1.png‎|thumb|none|500px|The sequence of clicks is indicated by yellow arrows with numbers. C is the center, a - major diameter, b - minor diameter, F1, F2 are foci.]]
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[[Image:Ellipse_3Point.png‎|thumb|none|500px|The sequence of clicks is indicated by red dots  with numbers. 1 is the periapsis, 2 is the apoapsis, 3 Defining point for minor diameter, green lines are major and minor diameters.]]
  
 
==Usage== <!--T:4-->
 
==Usage== <!--T:4-->
 
* Invoke the command by clicking a toolbar button, picking the menu item, or by using keyboard shortcut (needs to be assigned first in [[Interface Customization]]).
 
* Invoke the command by clicking a toolbar button, picking the menu item, or by using keyboard shortcut (needs to be assigned first in [[Interface Customization]]).
* First click in 3D view sets ellipse center. Second click sets the first radius and orientation of the ellipse. Third click sets the other radius (the distance from the line defined by first two clicks is the second radius).  
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* First click in 3D view sets a point that defines the crossing of the major diameter with the ellipse ( periapsis ). Second click in 3D view sets a point that defines the crossing of the major diameter with the ellipse opposite to the center point( apoapsis ). Third click sets a point on the ellipsis defining the minor radius.  
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* After the third click, the ellipse is created, together with a set of construction geometry aligned to it (major diameter, minor diameter, two foci). The construction geometry can be manually deleted if not needed, and recreated later. See [[Sketcher ConstrainInternalAlignment|Internal Alignment Constraint]] and [[Sketcher RestoreInternalAlignmentGeometry|Sketcher Show Hide Internal Geometry]].
 
* After the third click, the ellipse is created, together with a set of construction geometry aligned to it (major diameter, minor diameter, two foci). The construction geometry can be manually deleted if not needed, and recreated later. See [[Sketcher ConstrainInternalAlignment|Internal Alignment Constraint]] and [[Sketcher RestoreInternalAlignmentGeometry|Sketcher Show Hide Internal Geometry]].
 
* Pressing {{KEY|ESC}} or clicking the right mouse button cancels the function.
 
* Pressing {{KEY|ESC}} or clicking the right mouse button cancels the function.

Revision as of 10:33, 9 October 2018

Other languages:
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Under construction by HarryGeier


Sketcher CreateEllipse.svg Sketcher CreateEllipse

Menu location
Sketch → Sketcher geometries → Create ellipse by periapsis, apoapsis, minor radius
Workbenches
Sketcher, Part Design
Default shortcut
None
Introduced in version
-
See also
Sketcher Ellipse by center, Sketcher Circle, Sketcher Arc of Ellipse


Description

This tool draws an ellipse by picking three points: the Periapsis ( First crossing of longer diameter with ellipse), the Periapsis ( Second crossing of longer diameter with ellipse), one point on a side of the longer diameter defining the minor radius. When starting the tool, the mouse pointer changes to a white cross with a red ellipse icon. Besides are coordinates shown in real time.

The sequence of clicks is indicated by red dots with numbers. 1 is the periapsis, 2 is the apoapsis, 3 Defining point for minor diameter, green lines are major and minor diameters.

Usage

  • Invoke the command by clicking a toolbar button, picking the menu item, or by using keyboard shortcut (needs to be assigned first in Interface Customization).
  • First click in 3D view sets a point that defines the crossing of the major diameter with the ellipse ( periapsis ). Second click in 3D view sets a point that defines the crossing of the major diameter with the ellipse opposite to the center point( apoapsis ). Third click sets a point on the ellipsis defining the minor radius.
  • After the third click, the ellipse is created, together with a set of construction geometry aligned to it (major diameter, minor diameter, two foci). The construction geometry can be manually deleted if not needed, and recreated later. See Internal Alignment Constraint and Sketcher Show Hide Internal Geometry.
  • Pressing ESC or clicking the right mouse button cancels the function.

Peculiarities

  • Major and minor axes of ellipses are strict and cannot be swapped by resizing the ellipse. This is a consequence of the solver parametrization used (center (x,y), focus1 (x,y) and minor radius length (b)) and the same strict behavior of OpenCascade. The ellipse must be rotated to swap the axes.
  • Ellipse can function as a circle when its major and minor diameter lines are deleted, and one of the foci is constrained to coincide with the center. But radius constraint won't work on such a circle.
  • Moving the ellipse by edge is the same as moving ellipse's center.

Version

Introduced in FreeCAD v0.15.4309