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Description

This macro rotates the current view to point perpendicularly at a selected face of an existing object.

Usage

1. Select a face on an object
2. Run the macro

Script

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Macro_Align_View_to_Face.FCMacro

# -*- coding: utf-8 -*-
# Set the current view perpendicular to the selected line
# Place la vue perpendiculairement a la line selectionnee
# 2013 Jonathan Wiedemann,
# 2016 Werner Mayer, 
# 2022 tchernomax, https://forum.freecad.org/viewtopic.php?p=630019#p630019
# 2023 FreeCutter, modifications towards linked objects like in workbench Assembly 4 , https://forum.freecad.org/viewtopic.php?p=718516#p718516
#
__title__   = "Align_View_to_Face"
__author__  = "Jonathan Wiedemann (Rockn)"
__url__     = "https://www.freecad.org"
__Wiki__    = "https://wiki.freecad.org/Macro_Align_View_to_Face"
__version__ = "3.1"
__date__    = "2023/11/12"  #YYYY/MM/DD

from pivy import coin

import FreeCAD as app
import FreeCADGui as gui

def pointAt(normal, up):
    z = normal
    y = up
    x = y.cross(z)
    y = z.cross(x)
   
    rot = App.Matrix()
    rot.A11 = x.x
    rot.A21 = x.y
    rot.A31 = x.z
   
    rot.A12 = y.x
    rot.A22 = y.y
    rot.A32 = y.z
   
    rot.A13 = z.x
    rot.A23 = z.y
    rot.A33 = z.z

    return App.Placement(rot).Rotation

def get_selection_and_turn_view():
	doc = app.activeDocument()
	if doc is None:
		app.Console.PrintWarning('Align_view_to_face: No file open, nothing to do\n')
		return
	
	selection = gui.Selection.getSelectionEx('', 0) # Returns a vector of selection objects
	
	if not selection:
		app.Console.PrintWarning('Align_view_to_face: Nothing selected, nothing to do\n')
		return
	
	cam = FreeCADGui.ActiveDocument.ActiveView.getCameraNode()
	
	''' used to understand the 'getSelection' results
	for selection_object in selection:
		object_ = selection_object.Object
		sub_fullpaths = selection_object.SubElementNames
		if not sub_fullpaths:
			# An object is selected, not a face, edge, vertex.
			print(object_.Name)
		for sub_fullpath in sub_fullpaths:
			# One or more subelements are selected.
			print(object_.Name, sub_fullpath)
	'''
	
	sel = selection[0]
	face = sel.SubObjects[0]
	if face.Area == 0:			# trying to avoid errors due to wrong selected objects
		app.Console.PrintWarning('Align_view_to_face: Please select a face - not an edge or vertex\n')
		return
	dir = face.normalAt(0,0)
	
	if dir.z == 1 :
	    rot = pointAt(dir, App.Vector(0.0,1.0,0.0))
	elif dir.z == -1 :
	    rot = pointAt(dir, App.Vector(0.0,1.0,0.0))
	else :
	    rot = pointAt(dir, App.Vector(0.0,0.0,1.0))
	
	cam.orientation.setValue(rot.Q)
	gui.SendMsgToActiveView("ViewSelection")
	app.Console.PrintWarning('Align_view_to_face: Done\n')

if __name__ == '__main__':
	get_selection_and_turn_view()