Importing STL files shows all sorts of artifacts

Importing the HeartGears2-3.stl file from here: https://www.thingiverse.com/thing:243278/files using this code, has lots of artifacts, and holes in the outputed stl file. ```go package main import ( "github.com/hschendel/stl" "github.com/soypat/sdf/helpers/sdfexp" "github.com/soypat/sdf/render" ) func main() { solid, err := stl.ReadFile("HeartGears2-3.stl") if err != nil { panic(err) } tris := make([]render.Triangle3, len(solid.Triangles)) for i, t := range solid.Triangles { for k := 0; k < 3; k++ { tris[i][k].X = float64(t.Vertices[k][0]) tris[i][k].Y = float64(t.Vertices[k][1]) tris[i][k].Z = float64(t.Vertices[k][2]) } } object, err := sdfexp.ImportModel(tris, 0) if err != nil { panic(err) } err = render.CreateSTL("out.stl", render.NewOctreeRenderer(object, 500)) if err != nil { panic(err) } } ```