Part design sketch plane correct order: XY, YZ, ZX
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Part design sketch plane correct order: XY, YZ, ZX
Hi.
In my opinion, it is needed to modify one of the names of the planes (and its "orientation") one can select when making a sketch.
I think that instead of XY, XZ, YZ, the appropriate planes should be XY, YZ and ZX (in this order).
If i, j and k are unit vector along X, Y and Z axes respectively, vector algebra tell us that the following vector multiplications hold:
i x j = k, j x k = i and k x i = j
One of the effects of selecting XZ plane instead of the ZX is that the extrusions of the sketches on the former plane "grow" to the negative direction of the Y axis (by the way, i x k = - j ). Of course it can solved by inverting the extrusion sense, but it has not to be this way.
Regards
In my opinion, it is needed to modify one of the names of the planes (and its "orientation") one can select when making a sketch.
I think that instead of XY, XZ, YZ, the appropriate planes should be XY, YZ and ZX (in this order).
If i, j and k are unit vector along X, Y and Z axes respectively, vector algebra tell us that the following vector multiplications hold:
i x j = k, j x k = i and k x i = j
One of the effects of selecting XZ plane instead of the ZX is that the extrusions of the sketches on the former plane "grow" to the negative direction of the Y axis (by the way, i x k = - j ). Of course it can solved by inverting the extrusion sense, but it has not to be this way.
Regards
I have uploaded many FreeCAD video tutorials to my YouTube channel
Re: Part design sketch plane correct order: XY, YZ, ZX
That sounds sensible, and I frequently wondered why I had to reverse some directions of attached sketches. This might clarify things. From a systematic view it would be a change from alphabetic order to cyclic order.
However, I am not sure if this is compatible with current models. I am a big friend of clear basics, but if this was changed internally we need a migration concept as well.
However, I am not sure if this is compatible with current models. I am a big friend of clear basics, but if this was changed internally we need a migration concept as well.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
Re: Part design sketch plane correct order: XY, YZ, ZX
The common mnemonic is the right-hand rule: https://en.wikipedia.org/wiki/Right-hand_rule.
Why? It's just a matter of user interface, isn't it?
Extrusion based on sketch built according to the XZ plan is right.
Last edited by Opus on Tue Sep 11, 2018 6:19 am, edited 1 time in total.
- DeepSOIC
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Re: Part design sketch plane correct order: XY, YZ, ZX
current names are consistent with the way sketch axes are mapped to body/model axes.
XY: H_axis = X, V_axis = Y
XZ: H_axis = X, V_axis = Z
YZ: H_axis = Y, V_axis = Z
Now if we change to ZX, the sketch would end up in a very unnatural orientation. Renaming them just for sake of math doesn't help, IMO.
XY: H_axis = X, V_axis = Y
XZ: H_axis = X, V_axis = Z
YZ: H_axis = Y, V_axis = Z
Now if we change to ZX, the sketch would end up in a very unnatural orientation. Renaming them just for sake of math doesn't help, IMO.
Re: Part design sketch plane correct order: XY, YZ, ZX
I agree...
But I think this way FreeCAD would gain (a little of) math robutness...
I have uploaded many FreeCAD video tutorials to my YouTube channel
Re: Part design sketch plane correct order: XY, YZ, ZX
How about adding the third axis...?DeepSOIC wrote: ↑Mon Sep 10, 2018 8:39 am current names are consistent with the way sketch axes are mapped to body/model axes.
XY: H_axis = X, V_axis = Y
XZ: H_axis = X, V_axis = Z
YZ: H_axis = Y, V_axis = Z
Now if we change to ZX, the sketch would end up in a very unnatural orientation. Renaming them just for sake of math doesn't help, IMO.
XY: H_axis = X, V_axis = Y, Axis pointing to us Z
XZ: H_axis = X, V_axis = Z, Axis pointing to us -Y
YZ: H_axis = Y, V_axis = Z, Axis pointing to us X
XZ: H_axis = Z, V_axis = X, Axis pointing to us Y
But beyond the viewpoint of the sketches, the effect of extruding a sketch on XZ to -Y is inconsistent with the "other" extrusions modes and it seems to me inconvenient when designing.
I have uploaded many FreeCAD video tutorials to my YouTube channel
- DeepSOIC
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- Joined: Fri Aug 29, 2014 12:45 am
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Re: Part design sketch plane correct order: XY, YZ, ZX
I agree, but your proposal replaces this minor inconvenience with a major inconvenience. We can switch XZ to (-X)Z to get rid of both inconveniences, at a cost of another minor inconvenience.
Re: Part design sketch plane correct order: XY, YZ, ZX
Are you referring to the work of recoding or to any other mayor inconvenience?
I have uploaded many FreeCAD video tutorials to my YouTube channel
Re: Part design sketch plane correct order: XY, YZ, ZX
Well... "very unnatural orientation"... It is question of opinions (in my opinion )
I have to put on a balance "unnatural orientation" and and "extruding to a negative axis orientation"...
It would be good to have the option of choosing which of these "schemes" one want to use.
Last edited by jruiz on Mon Sep 10, 2018 10:55 am, edited 1 time in total.
I have uploaded many FreeCAD video tutorials to my YouTube channel