Croquizador CrearElipsePor3Puntos

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{{GuiCommand/es Name=Sketcher CreateEllipseBy3Points Name/es=Croquizador CrearElipsePor3Puntos |MenuLocation=Croquis → Geometrías del Croquizador → Crear elipse por 3 puntos |Workbenches=Croquizador |Version=0.15 |SeeAlso=Croquizador Elipse por el Central, Croquizador Círculo, Croquizador Arco de Elipse }}

Descripción

Esta herramienta dibuja una elipse eligiendo tres puntos : (1) la periapsis (primer cruce del diámetro mayor con la elipse), (2) la apoapsis (segundo cruce del diámetro mayor con la elipse), (3) un punto en un lado del diámetro mayor (a) que define el radio menor (b). (c) es el centro resultante y (f) son los puntos focales.

Al iniciar la herramienta, el puntero del ratón cambia a una cruz blanca con un icono de elipse roja.

The sequence of clicks is indicated by yellow arrows with numbers. 1 is the periapsis, 2 is the apoapsis, 3 is the defining point for minor diameter, green lines are major and minor diameters. Blue lines are random construction lines just for illustration purpose.

Utilización

  • Press the Ellipse by 3 points button.
  • 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.