StepKernel.cpp

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#include "StepKernel.h"
#include <iostream>
#include <fstream>
#include <chrono>
#include <sstream>
#include <map>
#include <functional>
#include <iomanip> // put_time
#include <cctype>

static std::string to_lower_copy(std::string str)
{
	for (auto &c : str)
		c = static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
	return str;
}

StepKernel::StepKernel()
{

}

StepKernel::~StepKernel()
{
}

StepKernel::EdgeCurve* StepKernel::create_edge_curve(StepKernel::Vertex * vert1, StepKernel::Vertex * vert2,bool dir)
{
	// curve 1
	auto line_point1 = new Point(entities, vert1->point->x, vert1->point->y, vert1->point->z);
	double vx = vert2->point->x - vert1->point->x;
	double vy = vert2->point->y - vert1->point->y;
	double vz = vert2->point->z - vert1->point->z;
	double dist = sqrt(vx * vx + vy * vy + vz * vz);
	vx = vx / dist;
	vy = vy / dist;
	vz = vz / dist;

	auto line_dir1 = new Direction(entities, vx, vy, vz);
	auto line_vector1 = new Vector(entities, line_dir1, 1.0);
	auto line1 = new Line(entities, line_point1, line_vector1);
	return new EdgeCurve(entities, vert1, vert2, line1, dir);
}

void StepKernel::build_tri_body(std::vector<double> tris,double tol, int &merged_edge_cnt, bool merge_planar)
{
	if (merge_planar)
	{
		build_tri_body_merged(tris, tol, merged_edge_cnt);
		return;
	}

	auto point = new Point(entities, 0.0, 0.0, 0.0);
	auto dir_1 = new Direction(entities, 0.0, 0.0, 1.0);
	auto dir_2 = new Direction(entities, 1.0, 0.0, 0.0);

	auto base_csys = new Csys3D(entities, dir_1, dir_2, point);
	std::vector<Face*> faces;
	std::map<std::tuple<double, double, double, double, double, double>, EdgeCurve*> edge_map;

	// vertices are shared between triangles: edge curves are reused by the
	// neighboring triangle, so without sharing the edges of a loop would
	// reference different vertex entities at the same location and the
	// resulting topology is rejected by strict readers
	std::map<std::tuple<double, double, double>, Vertex*> vertex_map;
	auto get_vertex = [&](const double *p) -> Vertex*
	{
		auto key = std::make_tuple(p[0], p[1], p[2]);
		auto it = vertex_map.find(key);
		if (it != vertex_map.end())
			return it->second;
		auto vert_point = new Point(entities, p[0], p[1], p[2]);
		auto vert = new Vertex(entities, vert_point);
		vertex_map[key] = vert;
		return vert;
	};

	for (std::size_t i = 0; i < tris.size() / 9; i++)
	{
		double p0[3] = { tris[i * 9 + 0],tris[i * 9 + 1] ,tris[i * 9 + 2] };
		double p1[3] = { tris[i * 9 + 3],tris[i * 9 + 4] ,tris[i * 9 + 5] };
		double p2[3] = { tris[i * 9 + 6],tris[i * 9 + 7] ,tris[i * 9 + 8] };

		double d0[3] = { 1,0,0 };
		d0[0] = p1[0] - p0[0];
		d0[1] = p1[1] - p0[1];
		d0[2] = p1[2] - p0[2];
		double dist0 = sqrt(d0[0] * d0[0] + d0[1] * d0[1] + d0[2] * d0[2]);
		if (dist0 < tol)
			continue;
		d0[0] = d0[0] / dist0;
		d0[1] = d0[1] / dist0;
		d0[2] = d0[2] / dist0;

		double d1[3] = { 1,0,0 };
		d1[0] = p2[0] - p0[0];
		d1[1] = p2[1] - p0[1];
		d1[2] = p2[2] - p0[2];
		double dist1 = sqrt(d1[0] * d1[0] + d1[1] * d1[1] + d1[2] * d1[2]);
		if (dist1 < tol)
			continue;
		d1[0] = d1[0] / dist1;
		d1[1] = d1[1] / dist1;
		d1[2] = d1[2] / dist1;

		// now cross
		// cross to get the thrid direction for the beam csys
		double d2[3] = { d0[1] * d1[2] - d0[2] * d1[1], d0[2] * d1[0] - d0[0] * d1[2], d0[0] * d1[1] - d0[1] * d1[0] };
		double dist2 = sqrt(d2[0] * d2[0] + d2[1] * d2[1] + d2[2] * d2[2]);
		if (dist2 < tol)
			continue;
		d2[0] = d2[0] / dist2;
		d2[1] = d2[1] / dist2;
		d2[2] = d2[2] / dist2;

		// correct the m direction
		double d1_cor[3] = { d2[1] * d0[2] - d2[2] * d0[1], d2[2] * d0[0] - d2[0] * d0[2], d2[0] * d0[1] - d2[1] * d0[0] };
		double d1_cor_len = sqrt(d1_cor[0] * d1_cor[0] + d1_cor[1] * d1_cor[1] + d1_cor[2] * d1_cor[2]);
		d1[0] = d1_cor[0] / d1_cor_len;
		d1[1] = d1_cor[1] / d1_cor_len;
		d1[2] = d1_cor[2] / d1_cor_len;


		// build the face
		// the 3 vertex locations
		auto vert1 = get_vertex(p0);
		auto vert2 = get_vertex(p1);
		auto vert3 = get_vertex(p2);

		EdgeCurve* edge_curve1 = 0;
		bool edge1_dir = true;
		get_edge_from_map(p0, p1, edge_map, vert1, vert2, edge_curve1, edge1_dir, merged_edge_cnt);

		EdgeCurve* edge_curve2 = 0;
		bool edge2_dir = true;
		get_edge_from_map(p1, p2, edge_map, vert2, vert3, edge_curve2, edge2_dir, merged_edge_cnt);

		EdgeCurve* edge_curve3 = 0;
		bool edge3_dir = true;
		get_edge_from_map(p2, p0, edge_map, vert3, vert1, edge_curve3, edge3_dir, merged_edge_cnt);

		std::vector<OrientedEdge*> oriented_edges;
		oriented_edges.push_back(new OrientedEdge(entities, edge_curve1, edge1_dir));
		oriented_edges.push_back(new OrientedEdge(entities, edge_curve2, edge2_dir));
		oriented_edges.push_back(new OrientedEdge(entities, edge_curve3, edge3_dir));

		// create the plane
		auto plane_point = new Point(entities, p0[0], p0[1], p0[2]);
		auto plane_dir_1 = new Direction(entities, d2[0], d2[1], d2[2]);
		auto plane_dir_2 = new Direction(entities, d0[0], d0[1], d0[2]);
		auto plane_csys = new Csys3D(entities, plane_dir_1, plane_dir_2, plane_point);
		auto plane = new Plane(entities, plane_csys);

		// build the faces

		auto edge_loop = new EdgeLoop(entities, oriented_edges);
		std::vector<FaceBound*> face_bounds;
		face_bounds.push_back(new FaceBound(entities, edge_loop, true));
		faces.push_back(new Face(entities, face_bounds, plane, true));
	}

	// build the model
	auto open_shell = new Shell(entities, faces);
	std::vector<Shell*> shells;
	shells.push_back(open_shell);
	auto shell_model = new ShellModel(entities, shells);
	auto manifold_shape = new ManifoldShape(entities, base_csys, shell_model);
}

void StepKernel::build_tri_body_merged(std::vector<double> tris, double tol, int &merged_edge_cnt)
{
	typedef std::tuple<double, double, double> PointKey;
	typedef std::tuple<double, double, double, double, double, double> EdgeKey;

	// gather valid triangles and their unit normals (computed from winding,
	// matching the non-merged path)
	std::vector<std::size_t> tri_ids;      // index into tris/9
	std::vector<double> tri_normals;       // 3 per entry in tri_ids
	for (std::size_t i = 0; i < tris.size() / 9; i++)
	{
		const double *p0 = &tris[i * 9 + 0];
		const double *p1 = &tris[i * 9 + 3];
		const double *p2 = &tris[i * 9 + 6];
		double v0[3] = { p1[0] - p0[0], p1[1] - p0[1], p1[2] - p0[2] };
		double v1[3] = { p2[0] - p0[0], p2[1] - p0[1], p2[2] - p0[2] };
		double dist0 = sqrt(v0[0] * v0[0] + v0[1] * v0[1] + v0[2] * v0[2]);
		double dist1 = sqrt(v1[0] * v1[0] + v1[1] * v1[1] + v1[2] * v1[2]);
		if (dist0 < tol || dist1 < tol)
			continue;
		double n[3] = { v0[1] * v1[2] - v0[2] * v1[1], v0[2] * v1[0] - v0[0] * v1[2], v0[0] * v1[1] - v0[1] * v1[0] };
		double nlen = sqrt(n[0] * n[0] + n[1] * n[1] + n[2] * n[2]);
		if (nlen / (dist0 * dist1) < tol) // degenerate/collinear triangle
			continue;
		tri_ids.push_back(i);
		tri_normals.push_back(n[0] / nlen);
		tri_normals.push_back(n[1] / nlen);
		tri_normals.push_back(n[2] / nlen);
	}
	std::size_t tri_cnt = tri_ids.size();

	// map each directed edge to the triangle that owns it; with consistent
	// STL winding a manifold interior edge appears once in each direction
	std::map<EdgeKey, std::size_t> directed_edge_tri;
	auto vert_of = [&tris](std::size_t tri_id, int corner) -> const double* {
		return &tris[tri_id * 9 + corner * 3];
	};
	auto make_edge_key = [](const double *a, const double *b) {
		return std::make_tuple(a[0], a[1], a[2], b[0], b[1], b[2]);
	};
	for (std::size_t t = 0; t < tri_cnt; t++)
		for (int c = 0; c < 3; c++)
			directed_edge_tri[make_edge_key(vert_of(tri_ids[t], c), vert_of(tri_ids[t], (c + 1) % 3))] = t;

	// union-find: merge triangles that share an edge and have parallel
	// normals; requiring adjacency keeps disjoint coplanar patches separate
	std::vector<std::size_t> parent(tri_cnt);
	for (std::size_t t = 0; t < tri_cnt; t++)
		parent[t] = t;
	std::function<std::size_t(std::size_t)> find_root = [&](std::size_t t) -> std::size_t {
		while (parent[t] != t)
		{
			parent[t] = parent[parent[t]];
			t = parent[t];
		}
		return t;
	};

	const double angular_tol = 1.0e-9; // on 1 - dot(n1,n2)
	for (std::size_t t = 0; t < tri_cnt; t++)
	{
		for (int c = 0; c < 3; c++)
		{
			auto rev_key = make_edge_key(vert_of(tri_ids[t], (c + 1) % 3), vert_of(tri_ids[t], c));
			auto it = directed_edge_tri.find(rev_key);
			if (it == directed_edge_tri.end())
				continue;
			std::size_t o = it->second;
			double dot = tri_normals[t * 3 + 0] * tri_normals[o * 3 + 0] +
				tri_normals[t * 3 + 1] * tri_normals[o * 3 + 1] +
				tri_normals[t * 3 + 2] * tri_normals[o * 3 + 2];
			if (dot < 1.0 - angular_tol)
				continue;
			std::size_t rt = find_root(t), ro = find_root(o);
			if (rt != ro)
				parent[rt] = ro;
		}
	}

	// bucket triangles by group root
	std::map<std::size_t, std::vector<std::size_t>> groups;
	for (std::size_t t = 0; t < tri_cnt; t++)
		groups[find_root(t)].push_back(t);

	auto point = new Point(entities, 0.0, 0.0, 0.0);
	auto dir_1 = new Direction(entities, 0.0, 0.0, 1.0);
	auto dir_2 = new Direction(entities, 1.0, 0.0, 0.0);
	auto base_csys = new Csys3D(entities, dir_1, dir_2, point);

	// shared topology across all faces
	std::map<PointKey, Vertex*> vertex_map;
	std::map<EdgeKey, EdgeCurve*> edge_map;
	auto get_vertex = [&](const double *p) -> Vertex* {
		auto key = std::make_tuple(p[0], p[1], p[2]);
		auto it = vertex_map.find(key);
		if (it != vertex_map.end())
			return it->second;
		auto pt = new Point(entities, p[0], p[1], p[2]);
		auto v = new Vertex(entities, pt);
		vertex_map[key] = v;
		return v;
	};

	std::vector<Face*> faces;
	int dropped_loops = 0;
	for (auto &grp : groups)
	{
		const std::vector<std::size_t> &members = grp.second;

		// boundary = directed edges whose reverse is not owned by this group
		std::map<PointKey, std::vector<std::pair<const double*, const double*>>> loop_start; // start vertex -> outgoing directed edges
		std::size_t boundary_cnt = 0;
		for (auto t : members)
		{
			for (int c = 0; c < 3; c++)
			{
				const double *a = vert_of(tri_ids[t], c);
				const double *b = vert_of(tri_ids[t], (c + 1) % 3);
				auto it = directed_edge_tri.find(make_edge_key(b, a));
				if (it != directed_edge_tri.end() && find_root(it->second) == grp.first)
					continue; // interior edge of this planar patch
				loop_start[std::make_tuple(a[0], a[1], a[2])].push_back(std::make_pair(a, b));
				boundary_cnt++;
			}
		}

		// chain directed boundary edges into closed loops; winding is
		// inherited from the triangles so holes stay clockwise
		std::vector<std::vector<std::pair<const double*, const double*>>> loops;
		while (boundary_cnt > 0)
		{
			// find any remaining edge to start a loop
			std::pair<const double*, const double*> start(0, 0);
			for (auto &kv : loop_start)
			{
				if (!kv.second.empty())
				{
					start = kv.second.back();
					kv.second.pop_back();
					boundary_cnt--;
					break;
				}
			}
			if (!start.first)
				break;
			std::vector<std::pair<const double*, const double*>> loop;
			loop.push_back(start);
			bool closed = false;
			while (true)
			{
				const double *tail = loop.back().second;
				if (tail[0] == start.first[0] && tail[1] == start.first[1] && tail[2] == start.first[2])
				{
					closed = true;
					break;
				}
				auto it = loop_start.find(std::make_tuple(tail[0], tail[1], tail[2]));
				if (it == loop_start.end() || it->second.empty())
					break; // open chain: non-manifold or inconsistent winding
				loop.push_back(it->second.back());
				it->second.pop_back();
				boundary_cnt--;
			}
			if (closed && loop.size() >= 3)
				loops.push_back(loop);
			else
				dropped_loops++;
		}
		if (loops.empty())
			continue;

		// plane csys from the group normal and the first boundary edge
		std::size_t t0 = members[0];
		const double *n = &tri_normals[t0 * 3];
		const double *l0a = loops[0][0].first;
		const double *l0b = loops[0][0].second;
		double ref[3] = { l0b[0] - l0a[0], l0b[1] - l0a[1], l0b[2] - l0a[2] };
		// Orthonormalize ref against the normal (matches the non-merged path's csys construction)
		double dotnr = ref[0] * n[0] + ref[1] * n[1] + ref[2] * n[2];
		ref[0] -= dotnr * n[0];
		ref[1] -= dotnr * n[1];
		ref[2] -= dotnr * n[2];
		double ref_len = sqrt(ref[0] * ref[0] + ref[1] * ref[1] + ref[2] * ref[2]);
		if (ref_len < tol)
		{
			// Fallback: pick any direction orthogonal to the normal
			double tmp[3] = { 0.0, 0.0, 1.0 };
			if (fabs(n[2]) > 0.9)
			{
				tmp[0] = 0.0; tmp[1] = 1.0; tmp[2] = 0.0;
			}
			ref[0] = tmp[1] * n[2] - tmp[2] * n[1];
			ref[1] = tmp[2] * n[0] - tmp[0] * n[2];
			ref[2] = tmp[0] * n[1] - tmp[1] * n[0];
			ref_len = sqrt(ref[0] * ref[0] + ref[1] * ref[1] + ref[2] * ref[2]);
		}
		auto plane_point = new Point(entities, l0a[0], l0a[1], l0a[2]);
		auto plane_dir_1 = new Direction(entities, n[0], n[1], n[2]);
		auto plane_dir_2 = new Direction(entities, ref[0] / ref_len, ref[1] / ref_len, ref[2] / ref_len);
		auto plane_csys = new Csys3D(entities, plane_dir_1, plane_dir_2, plane_point);
		auto plane = new Plane(entities, plane_csys);

		std::vector<FaceBound*> face_bounds;
		for (auto &loop : loops)
		{
			std::vector<OrientedEdge*> oriented_edges;
			for (auto &de : loop)
			{
				double a[3] = { de.first[0], de.first[1], de.first[2] };
				double b[3] = { de.second[0], de.second[1], de.second[2] };
				EdgeCurve *edge_curve = 0;
				bool edge_dir = true;
				get_edge_from_map(a, b, edge_map, get_vertex(de.first), get_vertex(de.second), edge_curve, edge_dir, merged_edge_cnt);
				oriented_edges.push_back(new OrientedEdge(entities, edge_curve, edge_dir));
			}
			face_bounds.push_back(new FaceBound(entities, new EdgeLoop(entities, oriented_edges), true));
		}
		faces.push_back(new Face(entities, face_bounds, plane, true));
	}

	if (dropped_loops)
		std::cout << "Warning: dropped " << dropped_loops << " open boundary chains (non-manifold or inconsistent winding)\n";
	std::cout << "Merged " << tri_cnt << " triangles into " << faces.size() << " planar faces\n";

	// build the model
	auto open_shell = new Shell(entities, faces);
	std::vector<Shell*> shells;
	shells.push_back(open_shell);
	auto shell_model = new ShellModel(entities, shells);
	auto manifold_shape = new ManifoldShape(entities, base_csys, shell_model);
}

void StepKernel::get_edge_from_map(
	double  p0[3],
	double  p1[3],
	std::map<std::tuple<double, double, double, double, double, double>, StepKernel::EdgeCurve *> &edge_map,
	StepKernel::Vertex * vert1,
	StepKernel::Vertex * vert2,
	EdgeCurve *& edge_curve,
	bool &edge_dir,
	int &merge_cnt)
{
	edge_curve = 0;
	edge_dir = true;
	auto edge_tuple1_f = std::make_tuple(p0[0], p0[1], p0[2], p1[0], p1[1], p1[2]);
	auto edge_tuple1_r = std::make_tuple(p1[0], p1[1], p1[2], p0[0], p0[1], p0[2]);
	if (edge_map.count(edge_tuple1_f))
	{
		edge_curve = edge_map[edge_tuple1_f];
		edge_dir = true;
		merge_cnt++;
	}
	else if (edge_map.count(edge_tuple1_r))
	{
		edge_curve = edge_map[edge_tuple1_r];
		edge_dir = false;
		merge_cnt++;
	}
	if (!edge_curve)
	{
		edge_curve = create_edge_curve(vert1, vert2, true);
		edge_map[edge_tuple1_f] = edge_curve;
	}
}

void StepKernel::write_step(std::string file_name, const std::string &unit, const std::string &schema)
{
	std::time_t tt = std ::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
	struct std::tm * ptm = std::localtime(&tt);
	std::stringstream iso_time;
	iso_time << std::put_time(ptm, "%FT%T");

	std::ofstream stp_file;
	stp_file.open(file_name);
	if (!stp_file)
		return;

	// up to 15 significant digits so double precision coordinates survive a
	// round trip (the stream default of 6 truncates them)
	stp_file << std::setprecision(15);

	// normalize the unit token; unknown tokens fall back to millimetres
	std::string u = to_lower_copy(unit);
	bool is_inch = (u == "in" || u == "inch" || u == "inches");
	std::string si_prefix = ".MILLI."; // SI_UNIT prefix for mm/cm/m
	if (u == "m" || u == "metre" || u == "meter")
		si_prefix = "$";
	else if (u == "cm" || u == "centimetre" || u == "centimeter")
		si_prefix = ".CENTI.";
	else if (!is_inch && !(u == "mm" || u == "millimetre" || u == "millimeter"))
		std::cout << "Unknown unit '" << unit << "', defaulting to mm\n";

	// default to AP203 unless the schema token requests 214
	std::string s = to_lower_copy(schema);
	bool ap214 = (s == "214" || s == "ap214");

	std::string author = "slugdev";
	std::string org = "org";

	// header info
	stp_file << "ISO-10303-21;\n";
	stp_file << "HEADER;\n";
	stp_file << "FILE_DESCRIPTION(('" << (ap214 ? "STEP AP214" : "STEP AP203") << "'),'2;1');\n";
	stp_file << "FILE_NAME('" << file_name << "','" << iso_time.str() << "',('" << author << "'),('" << org << "'),' ','stltostp',' ');\n";
	if (ap214)
		stp_file << "FILE_SCHEMA(('AUTOMOTIVE_DESIGN { 1 0 10303 214 1 1 1 1 }'));\n";
	else
		stp_file << "FILE_SCHEMA(('CONFIG_CONTROL_DESIGN'));\n";
	stp_file << "ENDSEC;\n";

	// data section
	stp_file << "DATA;\n";

	// entity ids may be non-contiguous after read_step, so start after the
	// largest id in use
	int next_id = 0;
	for (auto e : entities)
		next_id = std::max(next_id, e->id);
	next_id++;

	// declare the length unit of the model: an SI unit for mm/cm/m or a
	// conversion based unit for inches (ISO 10303-21 complex instances)
	int length_unit_id = 0;
	if (is_inch)
	{
		int si_mm_id = next_id++;
		int dim_exp_id = next_id++;
		int measure_id = next_id++;
		length_unit_id = next_id++;
		stp_file << "#" << si_mm_id << " = ( LENGTH_UNIT() NAMED_UNIT(*) SI_UNIT(.MILLI.,.METRE.) );\n";
		stp_file << "#" << dim_exp_id << " = DIMENSIONAL_EXPONENTS(1.,0.,0.,0.,0.,0.,0.);\n";
		stp_file << "#" << measure_id << " = MEASURE_WITH_UNIT(LENGTH_MEASURE(25.4),#" << si_mm_id << ");\n";
		stp_file << "#" << length_unit_id << " = ( CONVERSION_BASED_UNIT('INCH',#" << measure_id << ") LENGTH_UNIT() NAMED_UNIT(#" << dim_exp_id << ") );\n";
	}
	else
	{
		length_unit_id = next_id++;
		stp_file << "#" << length_unit_id << " = ( LENGTH_UNIT() NAMED_UNIT(*) SI_UNIT(" << si_prefix << ",.METRE.) );\n";
	}
	int angle_unit_id = next_id++;
	int solid_angle_unit_id = next_id++;
	int uncertainty_id = next_id++;
	int context_id = next_id++;
	stp_file << "#" << angle_unit_id << " = ( NAMED_UNIT(*) PLANE_ANGLE_UNIT() SI_UNIT($,.RADIAN.) );\n";
	stp_file << "#" << solid_angle_unit_id << " = ( NAMED_UNIT(*) SI_UNIT($,.STERADIAN.) SOLID_ANGLE_UNIT() );\n";
	stp_file << "#" << uncertainty_id << " = UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(1.0E-7),#" << length_unit_id
		<< ",'distance_accuracy_value','Maximum model space distance between geometric entities at asserted connectivities');\n";
	stp_file << "#" << context_id << " = ( GEOMETRIC_REPRESENTATION_CONTEXT(3) GLOBAL_UNCERTAINTY_ASSIGNED_CONTEXT((#" << uncertainty_id
		<< ")) GLOBAL_UNIT_ASSIGNED_CONTEXT((#" << length_unit_id << ",#" << angle_unit_id << ",#" << solid_angle_unit_id
		<< ")) REPRESENTATION_CONTEXT('Context #1','3D Context') );\n";

	// attach the unit context to the shape representation(s) so importers
	// interpret the coordinates in the requested unit
	for (auto e : entities)
		if (auto shape = dynamic_cast<ManifoldShape*>(e))
			shape->context_id = context_id;

	for (auto e : entities)
		e->serialize(stp_file);

	stp_file << "ENDSEC;\n";
	stp_file << "END-ISO-10303-21;\n";
	stp_file.close();
}

std::string StepKernel::read_line(std::ifstream &stp_file, bool skip_all_space)
{
	std::string line_str;
	bool leading_space = true;
	while (stp_file)
	{
		char get_char = ' ';
		stp_file.get(get_char);
		if (get_char == ';')
			break;

		if (get_char == '\n' || get_char == '\r' || get_char == '\t')
			continue;

		if (leading_space && (get_char == ' ' || get_char == '\t'))
			continue;
		if (!skip_all_space)
			leading_space = false;
		line_str.push_back(get_char);
	}
	return line_str;
}

void StepKernel::read_step(std::string file_name)
{
	std::ifstream stp_file;
	stp_file.open(file_name);
	if (!stp_file)
		return;

	// read the first line to get the iso stuff
	std::string iso_line = read_line(stp_file, true);

	bool data_section = false;
	std::vector<Entity*> ents;
	std::map<int,Entity*> ent_map;
	std::vector<std::string> args;
	while (stp_file)
	{
		std::string cur_str = read_line(stp_file, false);
		if (cur_str == "DATA")
		{
			data_section = true;
			continue;
		}
		if (!data_section)
			continue;

		if (cur_str == "ENDSEC")
		{
			data_section = false;
			break;
		}
		// parse the id
		int id = -1;
		if (cur_str.size() > 0 && cur_str[0] == '#' && cur_str.find('='))
		{
			auto equal_pos = cur_str.find('=');
			auto paren_pos = cur_str.find('(');
			auto id_str = cur_str.substr(1, equal_pos - 1);
			id = std::atoi(id_str.c_str());
			auto func_start = cur_str.find_first_not_of("\t ", equal_pos+1);
			auto func_end = cur_str.find_first_of("\t (", equal_pos + 1);
			auto func_name = cur_str.substr(func_start, func_end - func_start);

			// now parse the args
			auto arg_end = cur_str.find_last_of(')');
			auto arg_str = cur_str.substr(func_end + 1, arg_end - func_end - 1);
			Entity* ent = 0;
			if (func_name == "CARTESIAN_POINT")
				ent = new Point(entities);
			else if (func_name == "DIRECTION")
				ent = new Direction(entities);
			else if (func_name == "AXIS2_PLACEMENT_3D")
				ent = new Csys3D(entities);
			else if (func_name == "PLANE")
				ent = new Plane(entities);
			else if (func_name == "EDGE_LOOP")
				ent = new EdgeLoop(entities);
			else if (func_name == "FACE_BOUND")
				ent = new FaceBound(entities);
			else if (func_name == "FACE_OUTER_BOUND")
				ent = new FaceBound(entities);
			else if (func_name == "ADVANCED_FACE")
				ent = new Face(entities);
			else if (func_name == "FACE_SURFACE")
				ent = new Face(entities);
			else if (func_name == "OPEN_SHELL")
				ent = new Shell(entities);
			else if (func_name == "CLOSED_SHELL")
				ent = new Shell(entities);
			else if (func_name == "SHELL_BASED_SURFACE_MODEL")
				ent = new ShellModel(entities);
			else if (func_name == "MANIFOLD_SURFACE_SHAPE_REPRESENTATION")
				ent = new ManifoldShape(entities);
			else if (func_name == "VERTEX_POINT")
				ent = new Vertex(entities);
			else if (func_name == "SURFACE_CURVE")
				ent = new SurfaceCurve(entities);
			else if (func_name == "EDGE_CURVE")
				ent = new EdgeCurve(entities);
			else if (func_name == "ORIENTED_EDGE")
				ent = new OrientedEdge(entities);
			else if (func_name == "VECTOR")
				 ent = new Vector(entities);
			else if (func_name == "LINE")
				 ent = new Line(entities);

			if (ent)
			{
				ent->id = id;
				ent_map[id] = ent;
				ents.push_back(ent);
				args.push_back(arg_str);
			}
		}
		std::cout << cur_str << "\n";
	}
	// processes all the arguments
	for (int i = 0; i < ents.size(); i++)
	{
		ents[i]->parse_args(ent_map,args[i]);
	}
	stp_file.close();
}