Place window in a pitched roof object

[wearyhacker]

Hi,
Is there a reccomended way to place a window into a sloping face generated by the roof object?

I am struggling to consistently and accurately place windows into a sloping roof face. I have tried numerous different combinations of draft snaps and and working planes.
The best way I have come up with is to create a working plane for the roof face I am working with, turn off all the snaps.However with this method some mouse positions cause the window placement to rotate away from the roof plane and snap to a position parallel to one of the the global axis planes. This can be caused by a very small mouse movement.
Is there any way round this? It makes accurate placement difficult.

The follwoing are attempts to place a preset window in the interior face a of a sloping roof panel.

This is a mouse position that works

correct.png (5.92 KiB) Viewed 339 times

This is a mouse position that does not work.

vertical.png (4.82 KiB) Viewed 339 times

Thanks,

Roger

OS: Ubuntu 18.04 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.13528 (Git)
Build type: None
Branch: releases/FreeCAD-0-17
Hash: 5c3f7bf8ec51e2c7187789f7edba71a7aa82a88b
Python version: 2.7.15rc1
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedKingdom (en_GB)

[meme2704]

Selecting the side of the roof before selecting the window, it may be necessary to reposition it in X or Y

[wearyhacker]

Hi,
Thanks for the quick response. Sorry, I think my screenshots may have misled you. I have just realised that I must have deselected the face when taking the screen shot. It does not make any difference to the effect that I was trying to illustrate. I always select the face before I place a window, so that I ensure it is made a child of the correct object object. I also found that if I did not activate a working plane on the selected face then the window would be created at the correct orientation but placed with an origin on one of the global axes planes.
Roger

[wearyhacker]

Just for information here is what I get if I try the two different selections with no working plane set.

Screenshot from 2018-07-27 18-59-57.png (27.24 KiB) Viewed 325 times

I am just wondering if this is somehow related to how Freecad translates mouse positions into the 3d space. The usual way is to cast a ray from the camera position into the frustum passing through the near plane at a position defined by the mouse coordinates (translated). I wonder that if the ray intersects a global 3d coordinate frame before it intersects the roof plane then the window orientation/position gets mixed up. But that still does not explain why the orientation flip flops as you move the mouse cursor on the roof plane.

Roger