draw.Drawing

Methods

⌂ draw.Drawing

Method Reference: draw.Drawing.plot

draw.Drawing: plot (D)
draw.Drawing: plot (HAX, D)
draw.Drawing: plot (…, Name, Value)
draw.Drawing: H = plot (…)

Draw a draw.Drawing into a figure, to look at it.

draw.Drawing.plot (D) renders the drawing into the current axes at equal aspect ratio, honouring each entity’s layer, line type and colour.

draw.Drawing.plot (HAX, D) draws into the axes HAX instead of the current ones, as every plotting function in Octave accepts an axes handle ahead of its data. The 'Axes' pair below does the same thing and is equivalent.

H = draw.Drawing.plot (…) returns a column of graphics handles, one per object created, so that a caller can restyle or delete them.

Name/Value pairs

NameDefaultMeaning
'Axes'gcaaxes to draw into
'LineWidth'0.5width of every line, in points
'FontSize'8size of text, in points
'Layers'allcell array of layer names to draw
'Arc'64segments per full turn when sampling curves
'Hatch''lines''lines' to fill a hatch, 'boundary' for its outline alone
'Linetypes''true''true' to draw the real dash patterns, 'approximate' for the figure’s own four styles
'LTScale'1multiplies the dash lengths
'Margin'0.05blank space kept between the geometry and the axes, as a fraction of the drawing’s larger side; 0 fits the axes tight to the geometry
'FontScale'[]points per model unit; when given, each string is sized from its own entity height instead of from 'FontSize'
'DimScale'1multiplies the dimension ornament, which is a model dimension: a drawing meant for 1:50 wants 50 here, as it does in entities

Source Code: draw.Drawing

Why the axes do not fit tight

Auto-scaled limits stop exactly at the extreme coordinate, so an outline lying on it is drawn along the frame and reads as part of the axes rather than as geometry — which is the common case, not a corner one: a plate is usually dimensioned from its own edges. Both axes are therefore padded by the same absolute amount, which keeps the equal aspect ratio the drawing depends on, and that amount is 'Margin' times the larger of the two spans.

What you see is what gets written

The drawing is lowered through draw.Drawing.entities — the same conversion the DXF backend uses — and the result of that is what is plotted. A figure therefore shows the entities the file will contain, not a more flattering rendering of them. In particular a hatch appears as its boundary alone, because that is what the file will carry; the second output of draw.Drawing.entities says so explicitly.

The alternative, rendering from the drawing model directly, would let the screen show something the recipient never receives. For a package whose output is meant to be manufactured, that is the wrong way round.

Line types are drawn properly, not approximated

A figure offers four line styles and this package defines seven line types, so setting linestyle would collapse three of them onto their neighbours — CENTER, DASHDOT and PHANTOM would all come out dash-dot, and a phantom line would be indistinguishable from a centre line.

Instead each run of geometry is cut into its dashes and the pieces are drawn, so all seven patterns render as themselves. Dash lengths are in the units of the drawing, multiplied by 'LTScale', which is the model-space convention CAD uses. A drawing spanning tens of millimetres therefore needs no adjustment; one spanning metres wants an 'LTScale' to match.

The cost is one graphics object per dash. Set 'Linetypes' to 'approximate' on a large drawing to fall back on the figure’s four styles and one object per entity.

Text is not to scale by default. A figure sets font size in points, which does not track the data units the drawing is in, so text cannot both sit at the right size and stay there when the axes are zoomed. It is drawn at a fixed point size, positioned correctly.

That is right for a screen and wrong for a sheet, where a string must come out at the height the model gives it. Pass 'FontScale', in points per model unit, and each string is sized from its own entity height instead: at a plot scale of 1:S that factor is 72 / (25.4 * S), which is what draw.Drawing.print supplies. For a rendering where text is to scale by construction, use draw.Drawing.tikz.

See also: draw.Drawing, draw.Drawing.entities, draw.Drawing.tikz, dxf.write

Source Code: draw.Drawing

plot renders a drawing at equal aspect, honouring layer, line type and colour. It plots what entities produces, which is what the file backends write, so a figure shows what the recipient will get.

 D = draw.Drawing ('plate');
 D.Layer = 'OUTLINE';
 D = D.polyline ([0, 0; 80, 0; 80, 50; 0, 50], true);
 D = D.circle ([20, 25], 8).circle ([60, 25], 8);
 D.Layer = 'AXES';
 D.Linetype = 'CENTER';
 D.Colour = 'red';
 D = D.centremark ();
 D = D.line ([-8, 25], [88, 25]);
 plot (D);
 title ('a plate, its bores, and their centre lines');
plotted figure

All seven line types render as themselves, because each run is cut into its dashes rather than handed to one of the four styles a figure offers.

 D = draw.Drawing ();
 y = 0;
 for lt = draw.linetype ()
   D.Linetype = lt{1};
   D = D.line ([0, y], [70, y]);
   D.Linetype = 'CONTINUOUS';
   D = D.text ([74, y - 1], lt{1}, 2.5);
   y -= 8;
 endfor
 plot (D);
 title ('CENTER, DASHDOT and PHANTOM stay distinguishable');
plotted figure

An axes handle may lead, as for any plotting function, and Layers draws only what was asked for --- useful for checking one layer at a time.

 D = draw.Drawing ();
 D.Layer = 'PART';   D = D.circle ([0, 0], 20);
 D.Layer = 'DIMS';   D = D.diam ([0, 0], 20);
 figure ();
 subplot (1, 2, 1);
 plot (gca (), D);
 title ('both layers');
 subplot (1, 2, 2);
 plot (gca (), D, 'Layers', {'PART'});
 title ('the part alone');
plotted figure