Orientation of Y axis in Technical Drawings?

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yorik
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Re: Orientation of Y axis in Technical Drawings?

Postby yorik » Wed Jan 15, 2014 3:20 pm

Draft Dimensions are not based on Part... And they shouldn't, I think. Maybe we could modify that error message to tell something meaninful when someones tries to use it with Draft dims?
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Re: Orientation of Y axis in Technical Drawings?

Postby jmaustpc » Wed Jan 15, 2014 3:37 pm

yorik wrote:Draft Dimensions are not based on Part... And they shouldn't, I think. Maybe we could modify that error message to tell something meaninful when someones tries to use it with Draft dims?


At least it would be a good short term fix, a big help actually. :)

I forgot about the Draft insert tool once, I spent many months thinking dimensions was broken until Norm posted something with dimensions and had to ask him how he did it. When he told me, I realised I had previously known this but had then forgotten.

So in summary ... a reminder in the error message would solve the problem for me. :)
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Re: Orientation of Y axis in Technical Drawings?

Postby mrlukeparry » Wed Jan 15, 2014 7:18 pm

Thanks everyone for the extensive feedback and discussion!

I will implement the Drawing Page with the Y-axis pointing upwards from the bottom left.

In the end this isn't really a huge problem because it's only really used for the absolute position of views. Using QGraphicsView we get SVG for free, so I believe the coordinates will be transformed automatically if we wanted SVG for output.

In the case of units - my method before uses FreeCAD Units . If I read correctly, you can explicitly set the units used within QGraphicsView so we shouldn't have to worry about resolution independence.

jriegel wrote:Selection mean you can select lines points and so on in the drawing view (SVG elements).

Associativity mean you can add a "DatumFeature" to a selected line and points. This feature knows the "names" of the 2D SVG element they belong to and can be updated after a regeneration of the drawing view ( if the elements still exists).

That was the original plan, never got the time to do it...


Hopefully that is what I will achieve in the end - just not using SVG for the GUI.

TBH I wish we had someone implement a robust method for HLR - Hidden Line Removal so we could do the projection ourselves and have associativity with every edge and vertex of a part.

yorik wrote:One related thing I've been scratching my head with since a little time, one of the most-asked questions we hear here is certainly "how do I put dimensions on my drawing?". It is already possible, draft dimensions work fairly well now, but the problem is obviously that you must use the Draft tool instead of the normal Drawing tool to place them on the drawing sheet, which is far from obvious. But we absolutely can't make the Drawing module depend on something from the Draft module. So what could be a good solution to that? Any idea?


On this matter, I think we need to look at a more unified approach to 'dimensions' within FreeCAD. These might be 'strong' - lengths of edges in sketches or pads or 'weak' dimensions such as Annotations.

Eventually I would hope we can get the Drawing module to find automatically 'useful' datum dimensions within sketches aswell as with user made annotations. Similarly what would be useful is if we could collect all dimensions so that they could be referenced in equations (a bit like Pro/E Creo) or be used with optimisation problems. Perhaps maybe worthwhile discussing in another topic?
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yorik
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Re: Orientation of Y axis in Technical Drawings?

Postby yorik » Wed Jan 15, 2014 7:49 pm

That would work well for dimensionning a single object, but for ex. in architecture, where you need to dimension across many, many objects, there is no easy way to make it automatic...

But of course you are right, your work on dimensionning is the way to go. Draft dims are just a temporary placeholder! Anyway, yeah, that's certainly a subject for another topic :)
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Re: Orientation of Y axis in Technical Drawings?

Postby jriegel » Wed Jan 15, 2014 10:15 pm

+1
Stop whining - start coding!
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Re: Orientation of Y axis in Technical Drawings?

Postby ulrich1a » Wed Jan 15, 2014 11:16 pm

yorik wrote:Anyway, yeah, that's certainly a subject for another topic

I started one: viewtopic.php?f=10&t=5399#p43279

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Re: Orientation of Y axis in Technical Drawings?

Postby kwahoo » Thu Jan 16, 2014 4:44 pm

Hi,

I'm late, sorry - just my 2 cents. IMO QT approach is caused 30 years computer GUI legacy. I'm very happy that Luke is going to fix the coordinate system. CS's are very inconsistent:
- QT or Windows GDI is Y+ downwards, X+ rightwards, OpenGL is Y+ upwards
- OpenGL uses right-handed XYZ CS in 3D, Direct3D uses left-handed CS

Now imagine a app what can use OpenGL, Direct3D and software (GDI) rendering. It must be headache;)

Fortunately all CAD systems seems consistent. I cannot see fundamental differences between FreeCAD, Pro/E and Solidworks. Except this damn Drawing Workbench with Y+ downwards:)