Projecting Points - Drawing Module

Having started on dimensioning support I stumbled across quite an obvious problem, how would I do point to point  Dimensioning. Obviously I could extrapolate the points from the edges and use these, but any changes in the Base FreeCAD model and your dimensions would very easily mess-up. 

I started thinking about this last night and indeed to support such dimensioning modes with parametric relations, the points would have to be projected from the base FreeCAD model. I hit a brick wall trying to figure this out last night, but suddenly it came to me this morning. Sleep is a powerful thing. 

All I had to do is use the Projector algorithm to project points from project curves and then check if these can be referenced to the original object by checking if the topology exactly matches. 

The result is the above, all the points are recognised from the original object and now means we can in theory reference these. It is slightly dumb at the minute, because it projects points from all the edges (even if they are hidden). However, it should be trivial to fix this. 

Obviously in the GUI, the points will be hidden until an appropriate tool is used but is a step in the right direction indeed!

Easter break officially begins today and hopefully will have a helper who can assist me on the Drawing Module too *fingers crossed. 

Drawing Module: A Sneak Peak!

Having some time off this weekend, I have spent a bit of time further working on the experimental Drawing Module: I won't post the details of how I've got to where I am but I thought I would provide to you lucky guys a sneak peak at what I have currently achieved:

The left is the Drawing Module using QGraphicsView elements and the test model is on the right, although I am trying to work out why the projection isn't correct - maybe it's first angle projection? Also the edges that don't match up are arc of ellipses that aren't correct but that should be trivial to fix.

The point is I have manage to correctly project edges and rebuild nearly all the edge references from the original model, I found that on some occasions because a curve is broken up, the references can be lost but these are nearly always in 3D views, which would be difficult to dimension. It also supports edge selection and moving this projected view around the canvas despite there being no template.

The next step will be to tidy up the code and implement full interactivity and integration with FreeCAD's App::Property system, so that it can take advantage of the undo/redo framework.

 One of the frustrating things is not having anti-aliasing support in the opensource ATI drivers.

The Drawing Module: Part 2

As previously discussed the Drawing Module does it's job and produces the drawing our users require, but has its limitations. Now having some a little spare time every now and then in the evening, it seemed a nice little job in the mean time to experiment to see if we could improve this. How I envisage the Drawing Module to work is similar to what I've experienced in the past but relatively similar to its current behaviour.

Planned Workflow:

This is just an idea of the workflow I had in mind for using the Drawing Module.

1. Create Part/Assembly
2. Opens Drawing workbench
3. Creates Page Feature
4. Select template document and page properties (inherit data from FreeCAD document)
5. Select Part and create view (2D or 3D Projection, Section)
6. Add dimensions (attempt to import any sketcher dimensions - will require name framework)
7. Manipulate view features directly (move, 
8. Orthographic Projections can be created by dragging a projection in direction.
9. Provide a Measure tool for edges
10. Add Annotations to drawing
11. Provide a BOM or List of Parts

A note on page templates:

Currently the template would be kept as SVG so that this can be edited. I still don't know if these could be generalised so that it can be exported to another format but I don't think it would make much sense. However ideally it should be very easy to manipulate any 'placeholders' . This is not an immediate issue but I would speculate that the template placeholders would have a special edit mode to prevent any accidental changes by the user.

Below are the first jobs that need achieving for experimenting with a few ideas.

First Job: Low level shape storage

By unifying and abstracting the resultant shapes that are projected by Brep_HLR there is no restriction how these can be later represented. This means if the projected shape is a circle, we store the center point coordinates and its radius. This is extended to points, ellipses, b-spline form.

These can later be converted very easily into any other format whether .SVG, .DXF, Html Canvas or perhaps even Librecad may produce their own representation - who knows? 

It also allows us to represent this graphically in any way we want. Every time our part feature changes, this geometry is recalculated and can be then used in the user interface as needed.

Second Job: Building References

Looking more deeper into the projection code. Their algorithm seems to work by projecting all the edges and faces onto a projection plane, quite similar to an OpenGL projector. Then the algorithm sorts through all the edges and compares these with each project face to check if they are hidden.

Each edge and face is mapped from the original TopoDS_Shape and an index is built. By extracting these we can build up better integration so the drawing can have more interaction. I.e. we can extract edge lengths or update the projection without losing our annotations.

Third Job: Graphically Interface for Drawing

This could be done in SVG or using any other method. I prefer the use of QGraphicsView simply because it provides a framework for building up interactivity at a lower level which I don't think can be achieved in a web interface and should hopefully improve performance too. It would have been interesting to have used QML or QtQuick, but there are no objects available for drawing arbitrary shapes till Qt 5 and is more appropriate for dynamic interfaces. 

Conclusion:

Obviously there is more stuff that definitely needs considering, but this is at the moment an experiment to see what is feasible. In summary, what I am attempted is building a lower level data structure for storing geometry and reference data that can be exported and manipulated easily in any format. Then integrating this into QGraphicsView. 

Overtime I will report on my progress for what I have currently achieved in my spare time.