Importing SVG Drawings

SVG is the easiest way to get a 2D outline out of a drawing tool and into a script. You draw in Illustrator, Inkscape, Figma or a browser, save an SVG, and import it as OCCT wires or faces.

The importer does not support the whole SVG specification, and this page tells you where the edges are, so you can prepare a file that imports cleanly the first time.

What gets imported

Seven elements produce geometry:

path, rect, circle, ellipse, line, polyline, polygon

Nine more are recognised and deliberately skipped, because they hold definitions rather than drawings:

defs, symbol, clipPath, mask, marker, pattern, metadata, title, desc

Grouping elements such as g, a and switch are walked through, so geometry nested inside them comes across normally along with any transform they apply.

The import tells you what it could not use

The result carries a warnings array. Anything the importer met and could not turn into geometry is reported there, once per kind of element.

Read it. An SVG that imports as an empty scene is almost always explained by a single line in that array, and the alternative is guessing.

Two limitations worth knowing before you export

Reused symbols do not come across

The use element places a copy of something defined elsewhere in the document, usually inside defs. Since defs is skipped, a use element has nothing to point at, and contributes nothing.

This matters more than it sounds, because it is how most drawing tools export anything repeated: they define the shape once and place it twenty times. Such a file imports as an empty drawing.

What to do: in your drawing tool, expand, flatten or ungroup the repeated items before exporting, so each copy is written out as its own path.

Text is not geometry

text and tspan describe characters in a font, not outlines. Fonts are not available to the importer, so text cannot be turned into shapes.

What to do: convert text to paths or outlines before exporting. Every major drawing tool has this option, usually called "Convert to Outlines", "Object to Path" or "Create Outlines".

The same applies to image, which holds a raster picture, and foreignObject, which holds content that is not SVG at all. Neither has geometry to import.

Styling

Presentation attributes and inline style="..." are both read, and inherited down the tree the way you would expect.

An embedded <style> block with CSS selectors is not applied. Matching CSS selectors is a much larger job than reading attributes, and machine-generated SVG rarely uses them. If your file styles through a stylesheet, the import warns about it, and the fix is to export with presentation attributes instead - most tools have a setting for this.

Faces and holes

If you ask for faces rather than wires, the importer decides which outlines are holes inside other outlines, and which are separate shapes.

Two things decide it: whether one outline's centre lies inside another, and whether its area is genuinely smaller. Both are needed. The area comparison is what separates two circles drawn around the same centre, where the centre test alone cannot tell you which contains which.

Your drawing's own fill rule is respected, so a shape drawn with evenodd and one drawn with nonzero produce the hole arrangement you see in the drawing tool.

Arcs survive transforms

An arc inside a group that has been scaled, rotated or mirrored stays a true arc rather than being approximated. Mirroring reverses the direction the arc sweeps, which is handled, so a mirrored drawing does not come in with its curves bulging the wrong way.