Feature preview v0.16

[mozman]

This is a small preview of some features of the next version of ezdxf v0.16.

The focus of this new version was on improving the Path class and unify the methods to work with paths. The first improvement was to replace the different Path.from<Entity> methods by a simple make_path() function to create Path objects from many DXF types.

Next step was to add the reverse direction to create DXF entities from Path objects and helper functions to add them in a single step to a layout.

The new disassemble module creates graphic primitives from most DXF entities. These extra abstraction was chosen to represent linear entities like LINE, POLYLINE, SPLINES and mesh entities like MESH, POLYMESH and POLYFACE in a unified data structure. The new bbox module use this primitives to calculate bounding boxes for many entities in an easy way.

This are all low level features and do not sound very exciting in the first place, but in combination this creates advanced tools like creating HATCH entities from arbitrary DXF entities (complete source code).

Create some DXF entities:

msp = doc.modelspace()
attribs = { 'layer': 'FORMS'}

# Create DXF primitives:
msp.add_circle((2, 3), radius=2, dxfattribs=attribs)

# Ellipse with hole:
msp.add_ellipse((5, 0), major_axis=(3, 1), ratio=0.5, dxfattribs=attribs)
msp.add_circle((5, 0), radius=1.5, dxfattribs=attribs)

# Rectangle with a hole
rect = translate(box(3, 2), (3, 6))
msp.add_lwpolyline(rect, close=True, dxfattribs=attribs)
hole = translate(box(2, 1), (3.4, 6.4))
msp.add_lwpolyline(hole, close=True, dxfattribs=attribs)

Create HATCH entities form these DXF entities:

# Convert entities to primitives
primitives = disassemble.to_primitives(msp)

# Collect paths from primitives:
paths = [p.path for p in primitives if p.path]

# Render this paths as HATCH entities
path.render_hatches(msp, paths, dxfattribs={'layer': 'HATCHES', 'color': 2})

These hatches have only polygon paths, it is not possible to create edge paths by this method. This also prevents associative hatches, because the hatch has no corresponding source DXF entities.

This features are in beta stage but already merged into the master branch, so everyone can use it and send bug reports.

[mozman]

Added SPLINE edge support to Path() to HATCH conversion:

Which allows much smoother curve edges with less data:

[mozman]

The new text2path add-on provide some tools to convert text strings and text based DXF entities into outer- and inner Path objects.

These are SPLINE and POLYLINE entities created from text strings:

The letter "g" shows in detail the lossless Bèzier- into cubic B-spline curve conversion:

These are HATCH entities created from text strings displayed in TrueView (AutoCAD):

Text rendering depends on the font rendering engine used by the backend. The text2pathadd-on allows a direct comparison of the Matplotlib rendering (white HATCHES) and the TrueView text rendering (red text) The results are very accurate for short pieces of text:

Unfortunately, BricsCAD sometimes has problems rendering hatches with inner boundary paths as closed SPLINE edges:

It seems to depend on the position of the letters. I am assuming that it is a floating point precision problem. Here are some randomly placed "o" in BricsCAD:

Fortunately, the Matplotlib and PyQt backends work correctly.

cad_viewer.py (PyQt):

draw_cad.py (matplotlib):