// volume_stl.java   compile  javac -cp . read_stl.java
//                   compile  javac -cp . volume_stl.java
//                   execute  java  -cp . volume_stl  xxx.stl

public class volume_stl
{
  Boolean debug = false;
  int num_tri;
  double stl[][] = new double[20000][12];
  //           x1,y1,z1 x2,y2,z2 x3,y3,z3 nx,ny,nz
  //           0  1  2  3  4  5  6  7  8  9  10 11 

    
  public volume_stl(String filein)
  {
    int num_ptv[] = new int[1];
    int pt = 0;
    double xmin, xmax, ymin, ymax, zmin, zmax;
    double size = 1.0;     // make z positive 
    double area, avgz, vol, dvol, minz, znorm, tarea;
    double offs;


    System.out.println("volume_stl reading file "+filein);
    new read_stl(filein, stl, num_ptv);
    num_tri = num_ptv[0];
    System.out.println("num_tri= "+num_tri);
    xmin = stl[0][0];
    xmax = stl[0][0];
    ymin = stl[0][1];
    ymax = stl[0][1];
    zmin = stl[0][2];
    zmax = stl[0][2];
    for(int i=0; i<num_tri; i++)
    {
      pt = 0;
      for(int j=0; j<3; j++)
      {
	xmin = Math.min(xmin, stl[i][pt]);   // x1 x2 x3 j
	xmax = Math.max(xmax, stl[i][pt]);
	ymin = Math.min(ymin, stl[i][pt+1]); // y1 y2 y3 j
	ymax = Math.max(ymax, stl[i][pt+1]);
	zmin = Math.min(zmin, stl[i][pt+2]); // z1 z2 z3 j
	zmax = Math.max(zmax, stl[i][pt+2]);
        pt = pt+3;
      }
    }
    System.out.println("xmin="+xmin+", xmax="+xmax);
    System.out.println("ymin="+ymin+", ymax="+ymax);
    System.out.println("zmin="+zmin+", zmax="+zmax);
    System.out.println("[0] nx="+stl[0][9]+", ny="+stl[0][10]+", nz="+stl[0][11]);
    System.out.println("[n-1] nx="+stl[num_tri-1][9]+", ny="+stl[num_tri-1][10]+", nz="+stl[num_tri-1][11]);
    System.out.println(" ");
    System.out.println("compute volume and area ");

    vol = 0.0; // total volume 
    tarea = 0.0; // total area 

    if(zmin<0.0)
    {
      for(int j=0; j<num_tri; j++)
      {
        stl[j][2] = stl[j][2]-zmin; // z's must be positive 
        stl[j][5] = stl[j][5]-zmin; // z's must be positive 
        stl[j][8] = stl[j][8]-zmin; // z's must be positive
      }
    }

    for(int i=0; i<num_tri; i++)
    {
      avgz = (stl[i][2] + stl[i][5] + stl[i][8])/3.0;
      area = tri_area(i);
      znorm  = stl[i][11];
      tarea = tarea + area;
      dvol = area * znorm * avgz;
      vol = vol + dvol;
    }
    System.out.println("final total area ="+tarea+", total volume ="+Math.abs(vol));

    System.out.println(" ");
    System.out.println("volume_stl finished");
  }

  double tri_area(int i)
  {
    double d12, d23, d31, s;
    d12 = Math.sqrt((stl[i][0]-stl[i][3])*(stl[i][0]-stl[i][3])+  // x1 - x2
		    (stl[i][1]-stl[i][4])*(stl[i][1]-stl[i][4])+  // y1 - y2
		    (stl[i][2]-stl[i][5])*(stl[i][2]-stl[i][5])); // z1 - z2
    d23 = Math.sqrt((stl[i][3]-stl[i][6])*(stl[i][3]-stl[i][6])+  // x2 - x3
		    (stl[i][4]-stl[i][7])*(stl[i][4]-stl[i][7])+  // y2 - y3
		    (stl[i][5]-stl[i][8])*(stl[i][5]-stl[i][8])); // z2 - z3
    d31 = Math.sqrt((stl[i][6]-stl[i][0])*(stl[i][6]-stl[i][0])+  // x3 - x1
		    (stl[i][7]-stl[i][1])*(stl[i][7]-stl[i][1])+  // y3 - y1
		    (stl[i][8]-stl[i][2])*(stl[i][8]-stl[i][2])); // z3 - z1

    s = (d12+d23+d31)/2.0;
    return Math.sqrt(s*(s-d12)*(s-d23)*(s-d31));
  } // end area of triangle

  public static void main (String[] args)
  {
    new volume_stl(args[0]);
  }
} // end volume_stl.java