## Part design sketch plane correct order: XY, YZ, ZX

Have some feature requests, feedback, cool stuff to share, or want to know where FreeCAD is going? This is the place.
Forum rules
GeneFC
Posts: 1002
Joined: Sat Mar 19, 2016 3:36 pm
Location: Punta Gorda, FL

### Re: Part design sketch plane correct order: XY, YZ, ZX

jruiz wrote:
Fri Sep 14, 2018 11:54 am
sometimes what is called "common sense" by a group of persons is not exactly "common sense" for other people...
+1

I often say, "Common sense is one of the rarest things in the universe."

Gene
bill
Posts: 358
Joined: Fri Jan 09, 2015 9:25 pm

### Re: Part design sketch plane correct order: XY, YZ, ZX

Even considering your math proof, it is simply well accepted in all cad (I have seen/used quite a few), engineering, manufacturing, etc. environments I have ever been exposed; not just CAD. You will naturally find exceptions.

However, it is the NORM!
norm.png (14.85 KiB) Viewed 202 times
If included as an option, please make it an INVISIBLE OPTION; not to confuse and clutter the other 99.9_ percent; especially beginners.
chrisb
Posts: 15213
Joined: Tue Mar 17, 2015 9:14 am

### Re: Part design sketch plane correct order: XY, YZ, ZX

I had always thought this was THE NORM . The result would be the same.
jruiz
Posts: 43
Joined: Tue Oct 28, 2014 1:07 pm

### Re: Part design sketch plane correct order: XY, YZ, ZX

bill wrote:
Fri Sep 14, 2018 3:17 pm
...If included as an option, please make it an INVISIBLE OPTION; not to confuse and clutter the other 99.9_ percent; especially beginners.
It is very common in physics and mathematics to choose the first octant (X (+), Y (+), Z (+)) to study problem solutions. By the way, physics and mathematics are quite long-lived.
My hypothesis is the following:
I imagine that what could have happened with the CAD softwares was that the pioneers in this development, decided to choose to use the fourth octant (X (+), Y (-), Z (+)), of the eight in which Space is divided (some reason they would have to do it this way). After this, the users of these programs adapted to this scheme instead of continuing to use the old habit inherited from physics and mathematics. After some years of staying in this scheme, it is not surprising that some of these users defend this scheme as if it were the only and natural way to work without leaving space for any other option.

Regards
Jee-Bee
Posts: 1766
Joined: Tue Jun 16, 2015 10:32 am
Location: Netherlands

### Re: Part design sketch plane correct order: XY, YZ, ZX

Mathematics and physics have conventions. Engineering have conventions too. A lot of times they are related. But both have different working methods for also a lot of circumstances.

If you want a mathematical approach. I think you have to do it you're self because the (core) developers have other priorities.

Only tip I can give... what happens when another user with normal engineering configuration opens a file created by you....
jruiz
Posts: 43
Joined: Tue Oct 28, 2014 1:07 pm

### Re: Part design sketch plane correct order: XY, YZ, ZX

I propose that you do a little mental exercise with the help of another person who knows about Cartesian coordinate system but with no notions about any CAD software:
1.- Choose mentally any object, for example a car.
2.- Associate names up, down, left, right, forward and backward to the portions of the selected object as deemed appropriate.
3.- Place the object inside a rectangular parallelepiped of a suitable size so that the object barely fits.
4.- Finally, place the positive semi-axes + X, + Y and + Z coinciding with the axes in
where three edges of the parallelepiped rest.
5.- Repeat the exercise with other people.

DeepSOIC
Posts: 6527
Joined: Fri Aug 29, 2014 12:45 am
Location: Saint-Petersburg, Russia

### Re: Part design sketch plane correct order: XY, YZ, ZX

jruiz wrote:
Fri Sep 14, 2018 9:55 pm
I propose that you do a little mental exercise with the help of another person who knows about Cartesian coordinate system but with no notions about any CAD software
Let me try to convince myself I know nothing about CAD for a moment. Of course, it's not going to be perfect, but here's how I feel about it:
Inkedview from car_LI.jpg (163.15 KiB) Viewed 169 times
That is, Z is up (that's for sure!), X is to the right, Y is forward. For X,Y, I would choose them like that, because if I draw a coordinate axes on a sheet of paper and put the sheet onto the dashboard, that's how they orient.

I spent quite a bit of thinking when choosing placement marker for Lattice workbench. It was obvious that the straightforward indicator "axis cross with color-coded axes" is very difficult to interpret. It takes effort to recall, which color is which, and the orientation of the whole thing is often not quite clear by just looking at it, I have to give it a spin to pick up the actual 3d placement.
So eventually I arrived to a paperplane shape, because it's easy to remember which axis is which, and easy to quickly get a clue of how it's oriented.

The choice "X axis is direction of flight" was quite natural, but I think I even looked up conventions in aviation, just to be sure I won't have to remap them later when complaints from experts arise.

I think, it is quite important to stick to a fixed convention, at least because of this. Having a switchable convention for my paperplanes is simply not portable.
Jee-Bee
Posts: 1766
Joined: Tue Jun 16, 2015 10:32 am
Location: Netherlands

### Re: Part design sketch plane correct order: XY, YZ, ZX

I'm happy you choose rider perspective that's good. X axis is to the front; Y axis is think to the left and Z axis is to the top.
This all seen from rear axle since this is a stable point within every car. A car is basically lean down to the front compared to the ground and different per car... so not a option

@DeepSoic why didn't you make the same choose as your folded paper planes. Basically its the same situation.
Posts: 5331
Joined: Tue Jan 07, 2014 11:10 am
Contact:

### Re: Part design sketch plane correct order: XY, YZ, ZX

What abut the right hand rule for cnc milling?
Jee-Bee
Posts: 1766
Joined: Tue Jun 16, 2015 10:32 am
Location: Netherlands

### Re: Part design sketch plane correct order: XY, YZ, ZX

Even if you turn hand it still holds
It is easy to turn your hand so that x is horizontal; y is vertical and z is depth. that is fine but not following the CNC norm/ convention ...