// dat_to_stl.java   read  .dat file  3D, write  .stl file
//                         .dat needs all surface as triangles, tri_split

import java.io.*;
import java.util.*;
import java.text.*;

// needs  datread.java

// solid rect  sample  .stl  format
//   facet normal 0.0 0.0 -1.0
//     outer loop
//       vertex 1.0 1.0 1.0
//       vertex 5.0 4.0 1.0
//       vertex 1.0 4.0 1.0
//     endloop
//   endfacet
//   facet normal 0.0 0.0 -1.0
//     outer loop
//       vertex 1.0 1.0 1.0
//       vertex 5.0 1.0 1.0
//       vertex 5.0 4.0 1.0
//    endloop
//   endfacet
//...
// endsolid

public class dat_to_stl
{
  boolean debug = true;
  String solid = "solid";
  String facet = "facet";
  String normal = "normal";
  String outer = "outer";
  String loop = "loop";
  String vertex = "vertex";
  String endloop = "endloop";
  String endfacet = "endfacet";
  String endsolid = "endsolid";
  int pts, pt, k;
  int dpts[] = new int[20]; // needs poly_split for more than 3
  datread DR; // = new datread(filename); // defines data structures
  int num_points = 0; // set from datread
  int num_polys = 0; // set from datread
  double nx, ny, nz; // normal
  double x[] = new double[20];
  double y[] = new double[20];
  double z[] = new double[20];
    
  dat_to_stl(String filein, String fileout) // callable
  {
    System.out.println("datread.java reading "+filein);
    DR = new datread(filein); // defines data structures
    num_points = DR.num_points;
    num_polys = DR.num_polys;
    System.out.println("num_points="+num_points+
		       ", num_polys="+num_polys);
      
    try
    {
      BufferedWriter out = new BufferedWriter(new FileWriter(fileout));
      PrintWriter fout = new PrintWriter(out);
      
      fout.println("solid "+fileout);
      System.out.println("print polygons");
      k = 0; // polygons
      for(int i=0; i<DR.num_polys; i++)
      {
        pts = DR.data_polys[k++];
        System.out.print(+pts); // no cr
	for(int j=0; j<pts; j++)
	{
	  pt = DR.data_polys[k++];
	  System.out.print(" "+ pt);
	  dpts[j] = pt-1;
	  x[j] = DR.data_points[dpts[j]].x ;
	  y[j] = DR.data_points[dpts[j]].y ;
	  z[j] = DR.data_points[dpts[j]].z ;
	} // end j  pts
	System.out.println(" ");
	normal(x, y, z); // only uses first 3
        for(int j=0; j<pts-2; j++)  // first used as last
	{
	  if(pts>3 && j==pts-3)
	  {
	      System.out.println("vert "+(dpts[j+0]+1)+
				     " "+(dpts[j+1]+1)+
				     " "+(dpts[0]+1));
	  }
	  else
	  {
	      System.out.println("vert "+(dpts[j+0]+1)+
				     " "+(dpts[j+1]+1)+
				     " "+(dpts[j+2]+1));
	  }
          if(pts>3 && j==pts-3)
          {
            System.out.println("xyz "+x[j+0]+" "+y[j+0]+" "+z[j+0]);
            System.out.println("xyz "+x[j+1]+" "+y[j+1]+" "+z[j+1]);
            System.out.println("xyz "+x[0]  +" "+y[0]+  " "+z[0]);
	  }
	  else
	  {
            System.out.println("xyz "+x[j+0]+" "+y[j+0]+" "+z[j+0]);
            System.out.println("xyz "+x[j+1]+" "+y[j+1]+" "+z[j+1]);
            System.out.println("xyz "+x[j+2]+" "+y[j+2]+" "+z[j+2]);
	  }
	  if(pts>3 && j==pts-3)
	  {
	    System.out.println("normal x="+nx+", y="+ny+", z="+nz);
            fout.println("  facet normal "+nx+" "+ny+" "+nz+" ");
            fout.println("    outer loop");
            fout.println("      vertex "+x[j+0]+" "+y[j+0]+" "+z[j+0]+" ");
            fout.println("      vertex "+x[j+1]+" "+y[j+1]+" "+z[j+1]+" ");
            fout.println("      vertex "+x[0]+" "  +y[0]+" "  +z[0]+" ");
            fout.println("    endloop ");
            fout.println("  endfacet ");
	  }
	  else
	  {
	    System.out.println("normal x="+nx+", y="+ny+", z="+nz);
            fout.println("  facet normal "+nx+" "+ny+" "+nz+" ");
            fout.println("    outer loop");
            fout.println("      vertex "+x[j+0]+" "+y[j+0]+" "+z[j+0]+" ");
            fout.println("      vertex "+x[j+1]+" "+y[j+1]+" "+z[j+1]+" ");
            fout.println("      vertex "+x[j+2]+" "+y[j+2]+" "+z[j+2]+" ");
            fout.println("    endloop ");
            fout.println("  endfacet ");
	  }

        } // end j  pts
      } // end i  num_polys
      fout.println("endsolid");
      out.close();
    } // end try
    catch(IOException exception)
    {
      System.out.println("dat_to_stl.java "+exception);
    }
    System.out.println("dat_to_stl.java wrote "+fileout);
  } // end dat_to_stl

  void normal(double x[], double y[], double z[]) // of triangle
  {
    double ax, ay, az, bx, by, bz, ss; // nx, ny, nz global

    ax = x[2] - x[0];
    ay = y[2] - y[0];
    az = z[2] - z[0];
    bx = x[1] - x[0];
    by = y[1] - y[0];
    bz = z[1] - z[0];
    nx = ay*bz-az*by;
    ny = az*bx-ax*bz;
    nz = ax*by-ay*bx;
    ss = Math.sqrt(nx*nx+ny*ny+nz*nz);
    nx = nx / ss;
    ny = ny / ss;
    nz = nz / ss;
  } // end normal
    
  public static void main (String[] args)
  {
    new dat_to_stl(args[0],args[1]); // .dat  .stl
  }
} // end class dat_to_stl