diff --git a/internal/mapfmt/toseg.go b/internal/mapfmt/toseg.go
new file mode 100644
index 0000000..708f873
--- /dev/null
+++ b/internal/mapfmt/toseg.go
@@ -0,0 +1,18 @@
+package mapfmt
+
+import "bspviz/internal/geom" // anpassen
+
+func LinedefsToSegs(verts []Vertex, lines []Linedef) []geom.Seg {
+	segs := make([]geom.Seg, 0, len(lines))
+	for _, L := range lines {
+		a := verts[L.V1]
+		b := verts[L.V2]
+		A := geom.V(float64(a.X), float64(a.Y))
+		B := geom.V(float64(b.X), float64(b.Y))
+		if geom.Len(geom.Sub(B, A)) < 1e-9 {
+			continue // degenerat
+		}
+		segs = append(segs, geom.Seg{A: A, B: B})
+	}
+	return segs
+}