Convert SVG to OBJ

Each shape becomes its own object

A drawing is usually several things — a logo mark and its lettering, a row of parts on a sheet, the pieces of a sign. Each drawing element becomes a separate named object in the OBJ, using the id from the SVG where it has one, so you can move them independently the moment the file opens.

A shape and its holes stay together, because they are one object with a hole in it rather than two objects. A word drawn as a single path stays one object too, even though it is twenty-six separate loops — that is what the person who drew it meant by putting them in one element.

A drawing with a very large number of separate shapes — a traced photograph, say — is merged into one object instead. A list of nine hundred entries is not a list anybody can use.

The mesh is properly built

Extruding an outline naively gives you a pile of loose triangles that do not know they are neighbours. This one is welded first, so points that sit in the same place become one point, and then the normals are rebuilt from the geometry with a thirty degree crease angle — the same threshold Blender uses.

The practical effect is that the flat faces stay flat and the extruded edge stays sharp, while a curved edge shades smoothly round the curve. You can select an edge loop, bevel it, or subdivide it, and nothing falls apart.

Curves become straight lines, finely

Nothing in an OBJ is curved. A Bézier in your SVG becomes a series of straight segments, and how many depends on how much the curve actually bends and how large the drawing is. The tolerance is set from the size of the whole drawing, so a small rounded corner and a large circle come out equally smooth.

If you want fewer triangles, simplify the paths in your drawing program before converting. If you want more, scale the drawing up — the flattening follows the size.

Units and which way is up

OBJ records no units, and modelling programs usually treat one unit as one metre. Your drawing is read in millimetres, so leave the output unit at millimetres if you want the numbers to match the drawing, or set it to metres if you are about to drop the model into a scene built at real-world scale.

The extruded shape lies in the XY plane with its thickness going up Z, which is how a flat thing sits in a CAD program or a slicer. Blender and most modelling programs want Y up instead, so set the output up-axis to Y and the model arrives standing the way that program expects.