"description"

[ "description", "label", [x1, y1], [x2, y2], gap, startgap ]

Label with a leader line, e.g. a friction coefficient pointing at a rough surface.

• "label" text, typeset in MathJax math mode (e.g. "\\mu_0=0.3"; spaces become small math spaces, as in all meclib labels)
• [x1, y1] start point of the line, e.g. on the surface
• [x2, y2] center of the label
• gap (optional, default 4) space in pixels between the end of the line and the label's bounding box
• startgap (optional, default 0) space in pixels between [x1, y1] and the start of the line

The line runs from the start point towards the label center and stops gap pixels before the label, so it never touches the text. Its end point is computed from the label's size: first estimated from the TeX source, then measured once MathJax has typeset the label. If the label covers the whole distance, no line is drawn.

[
  ["grid", "", "", -1, 9, -1, 6, 50],
  ["wall", "", [0, 1], [8, 1], -45],
  ["description", "\\mu_0=0.3", [1, 1], [2, 2.5]],
  ["description", "\\mu", [3, 1], [3, 2.5]],
  ["description", "\\mu=\\frac{1}{2}", [7, 1], [6.5, 3.5]],
  ["description", "\\text{rough}", [2, 4], [4, 4.5], 4, 6],
  ["point", "P", [2, 4]]
]

The object is not interactive and has no state. The test scene tests/scenes/obj_description.json contains this example.