Lines and dimensions

Defined in src/dd_dimlines.scad.

line

line(length, width = DIM_LINE_WIDTH, height = DIM_LINE_HEIGHT, left_arrow = false, right_arrow = false,
     vert = false, color = DEF_LINE_COLOR)

Draws a straight line from the origin along +X, with an optional arrowhead at either end.

Parameter	Meaning
length	Total length, arrowheads included
width	Line width
height	Z thickness
left_arrow	Arrowhead at the origin end
right_arrow	Arrowhead at the far end
vert	Draw along +Y instead of +X
color	Line colour

The line starts at the origin and is centred on its axis across its width. That makes a line easy to place by its start point, and lets two lines meet at a corner without a half-width correction.

An arrowhead is 4 line widths across.

include <DraftSCAD/dimdraft.scad>

line(length = 2);
translate([ 0, -0.3, 0 ]) line(length = 2, left_arrow = true);
translate([ 0, -0.6, 0 ]) line(length = 2, right_arrow = true);
translate([ 0, -0.9, 0 ]) line(length = 2, left_arrow = true, right_arrow = true);
translate([ 2.5, -0.9, 0 ]) line(length = 0.9, vert = true);

arrow

arrow(arr_points, arr_length, height, color = DEF_LINE_COLOR)

Draws one arrowhead with its tip at the origin, pointing toward −X. line() uses it; you rarely need it directly.

Parameter	Meaning
arr_points	Width across the barbs, and the distance from tip to barbs
arr_length	Distance from the tip to the notch at the back of the head
height	Z thickness

dimensions

dimensions(length, line_width = DIM_LINE_WIDTH, line_height = DIM_LINE_HEIGHT, loc = DIM_CENTER,
           color = DEF_LINE_COLOR, text_color = DEF_TEXT_COLOR)

Draws a dimension line from the origin along +X, length long, labelled with length.

Parameter	Meaning
length	The distance to dimension, and the label
loc	Where the label goes; see below

loc	Result
DIM_CENTER	Arrows point outward to both ends, with the label in a gap in the middle
DIM_LEFT	One unbroken line with an arrow at each end, label to the left
DIM_RIGHT	One unbroken line with an arrow at each end, label to the right
DIM_OUTSIDE	Two arrows outside the distance pointing inward, label between them

Use DIM_LEFT, DIM_RIGHT or DIM_OUTSIDE when the distance is too short to hold the label.

If you do not, the module handles it. A DIM_CENTER dimension with no room for its label and two arrows is drawn in the DIM_OUTSIDE form. If the label does not fit between the arrows either, it goes to the right of them.

include <DraftSCAD/dimdraft.scad>

length = 2.5;

// two vertical lines to mark the distance being dimensioned
line(length = 2.2, vert = true);
translate([ length, 0, 0 ]) line(length = 2.2, vert = true);

locs = [ DIM_CENTER, DIM_LEFT, DIM_RIGHT, DIM_OUTSIDE ];
for (i = [0:3])
    translate([ 0, 0.3 + 0.5 * i, 0 ]) dimensions(length, loc = locs[i]);

Things to know:

• The label is always str(length). There is no way to add a prefix, a tolerance or units, or to set the precision.
• A dimension is always horizontal. For a vertical one, wrap it in rotate([ 0, 0, 90 ]); the label rotates with it.
• The module does not draw extension lines. Draw those with line().
• The room a label needs comes from dd_text_units(), an estimate that is exact for numbers in the default font.

dd_text_units

dd_text_units(text)

A function. It estimates the width of a string in font units, at OpenSCAD’s default text size of 10. Multiply by DIM_FONTSCALE for the width as drawn.

It counts 7.724 for every character except a period or a space, which count 3.859. Those are the advances of the digits, the period and the space in the default font, so the result is exact for a number: dd_text_units("3.53") is 27.031. It is only approximate for letters, which vary in width, and for any other font.

The library estimates the width and does not call textmetrics(), so it needs nothing newer than OpenSCAD 2021.01.

leader_line

leader_line(angle, radius, angle_length, horz_length, direction = DIM_RIGHT, line_width = DIM_LINE_WIDTH,
            line_height = DIM_LINE_HEIGHT, text = "", do_circle = false, color = DEF_LINE_COLOR,
            text_color = DEF_TEXT_COLOR)

Draws an arrow pointing at the origin from a given angle, a horizontal shoulder, and a label.

Parameter	Meaning
angle	Direction of the angled segment, in degrees from +X
radius	Distance from the origin to the arrow tip
angle_length	Length of the angled segment
horz_length	Length of the horizontal shoulder
direction	DIM_RIGHT or DIM_LEFT: which way the shoulder and label extend
text	The label; leave it out to draw the line alone
do_circle	Draw a circle around the label, for a balloon number

Translate to the centre of the feature first. To point at the rim of a hole, pass the hole’s radius as radius. To point at a spot, pass radius = 0.

include <DraftSCAD/dimdraft.scad>

radius = 0.5;
circle_center(radius);

leader_line(angle = 30, radius = radius, angle_length = 0.75, horz_length = 0.5, text = "to the right");
leader_line(angle = 150, radius = radius, angle_length = 0.75, horz_length = 0.5, direction = DIM_LEFT,
            text = "to the left");
leader_line(angle = -45, radius = radius, angle_length = 1, horz_length = 0.25, text = "1", do_circle = true);

The circle is centred on the label and its edge meets the end of the shoulder line. Its size comes from dd_text_units(), so it fits a number; a label of letters may sit off-centre in it.

circle_center

circle_center(radius, size = DIM_HOLE_CENTER, line_width = DIM_LINE_WIDTH, line_height = DIM_LINE_HEIGHT,
              color = "grey")

Marks the centre of a circle at the origin: a cross at the centre, and a short tick across the circle on each axis.

Parameter	Meaning
radius	Radius of the circle being marked
size	Length of each mark

include <DraftSCAD/dimdraft.scad>

radius = 0.5;

difference()
{
    cube([ 2, 2, 1 ], center = true);
    cylinder(h = 2, r = radius, center = true, $fn = 100);
}

// drawn just above the top face
translate([ 0, 0, 0.5 ]) circle_center(radius);

The module does not draw centre lines across the part. Add those with line() if you want them.