public function writeStl($ps_stl)
{
// truncate file
if (@file_put_contents($ps_stl, "") === false) {
return false;
// probably permission error
}
if (sizeof($this->opa_faces) < 1 || sizeof($this->opa_vertices) < 1) {
return false;
// invalid ply or not parsed yet
}
$vo_handle = @fopen($ps_stl, "w");
fwrite($vo_handle, "solid collectiveaccess_generated_stl\n");
foreach ($this->opa_faces as $vs_face) {
// calculate normal (the 'right hand rule')
// have to unpack from strings first
$pa_unpack = unpack("I*", $vs_face);
$p1 = array_values(unpack("f*", $this->opa_vertices[$pa_unpack[1]]));
$p2 = array_values(unpack("f*", $this->opa_vertices[$pa_unpack[2]]));
$p3 = array_values(unpack("f*", $this->opa_vertices[$pa_unpack[3]]));
$u = PlyToStl::vec_sub($p2, $p1);
$w = PlyToStl::vec_sub($p3, $p1);
$n = PlyToStl::vec_crossprod($u, $w);
// add triangle
fprintf($vo_handle, "facet normal %f %f %f\n", $n[0], $n[1], $n[2]);
fwrite($vo_handle, " outer loop\n");
fprintf($vo_handle, " vertex %f %f %f\n", $p1[0], $p1[1], $p1[2]);
fprintf($vo_handle, " vertex %f %f %f\n", $p2[0], $p2[1], $p2[2]);
fprintf($vo_handle, " vertex %f %f %f\n", $p3[0], $p3[1], $p3[2]);
fwrite($vo_handle, " endloop\n");
fwrite($vo_handle, "endfacet\n");
}
file_put_contents($ps_stl, "endsolid collectiveaccess_generated_stl\n", FILE_APPEND);
return true;
}
