Rotated Views Curiousity

[rich61]

This isn't a bug, just a curiosity.

I have a mounting plate for other parts that is angled on the transom of a boat. I made the model in the orientation that it is used. However I want to View position and dimension it differently, as though it is fixtured on the milling table at an angle.

It was padded the DrawnView which is the application orientation. CW_2 is the fixtured orientation. I labeled Side A and Side B. The rotations are by using the CW and CCW arrows in the 'cube'. Notice from the hidden lines, while the plate is angled, the hole is horizontal. For the milling hole positions, I need to make horizontal dimensions where the machine spindle enters Surface A. I can use cosmetic lines to locate the center of the hole and place a TechDraw vertex at the intersection, and then show my horizontal dimensions.

I was just wondering how the vertex placement works. I was surprised TechDraw Vertices didn't stay on one side or the other, and also that they don't appear on the AsDrawnView.

DrawnView shows no TechDraw vertices
CW_2 shows vertices on Side B
CCW_2 shows vertices on Side A

TechDrawRotatedViews.png (77.93 KiB) Viewed 568 times

Code: Select all

OS: Ubuntu 22.04.2 LTS (ubuntu:GNOME/ubuntu)
Word size of FreeCAD: 64-bit
Version: 0.21.0.32926 (Git) AppImage
Build type: Release
Branch: master
Hash: 78bdc3499647dcce97fc893b08a7b323b8067038
Python 3.11.3, Qt 5.15.8, Coin 4.0.0, Vtk 9.2.2, OCC 7.7.0
Locale: English/United States (en_US)
Installed mods: 
  * Assembly3 1.0.3

[bensay]

I am not sure, if I am decoding your steps correctly. To me, it sounds like you tried adding cosmetic geometry on one view and then expected the cosmetic geometry also to show up on the other views - and you are asking why this isn't happening.

All the views are 2D representations that are drawn from 2D data. The 2D data are produced from the 3D shape. When you are adding cosmetic geometry, you are essentially more 2D data to the view. This cosmetic data is not ported backwards to the 3D shape. The cosmetic data itself is also 2D; this means that there is no data on how the cosmetic geometry would be equivalently positioned in 3D even if we wanted to port it back to the 3D shape such that it could show up on the other views as well.

Any point in the TechDraw view is only known in 2D projected locations. A point is stored as (x; y) referencing the paper. Making a cosmetic line between two points are then (x; y) -> (x; y). There is no 3rd dimensional data that can be ported back to the 3D shape and used when projecting the other views. Hence, 2D cosmetic geometry is limited to be on a single view on how TechDraw graphics are internally designed.

Was this what you were asking for? Please attach your file if not.

[chrisb]

Selecting a face before creating a TechDraw view aligns the view to that face.
In case it is rotated along the viewing axis, look at this topic: viewtopic.php?t=76897#p668649.

[chrisb]

It took a bit of searching: here is another method to align views. It can help with tricky cases, but requires a bit of work.

[rich61]

First, Chris, selecting the surface: Yes I do that all the time. However all these views are on edge. So that isn't an issue. They are all orthogonal to the view.

See the view below, with some dimensions. If I zero my milling machine spindle at the top left edge of the plate edge of the drawing, then the position to bore the large hole is 4.787". If I zero the spindle at the lower left edge of the plate, then the position is 4.891 on my digital readout. Keep in mind that the plate is depicted as being fixtured at the angle, and the mill table moves horizontally, so I need a horizontal dimension not an aligned dimension, so that I pierce the surface A at the correct point.

In this updated view, I did use the cosmetic system to draw a line between two parallels where the parallels are the hidden lines of the large hole. Then I used the cosmetic system to create a vertex at the intersection of that hole center-line, and the surface of the plate. And I dimension from that.

you tried adding cosmetic geometry on one view and then expected the cosmetic geometry also to show up on the other views

No, that isn't what I was expecting. I was expecting that TechDraw vertices would always be on the same side regardless of my rotated views. The vertices in the previous drawings were all created by TechDraw automatically, I didn't add them.

Again, this isn't a bug or a problem for me, as you see below I can get the dimensions that I need for the milling setup.

CW_2.png (11.09 KiB) Viewed 518 times

Chris, I just now see you added another reference to align views which I'll look at. But that isn't the issue I was curious about. I was initially thinking that the pattern of vertices automatically created by TechDraw would be a good visual indicator of which side is which. It isn't but not a big deal.