Example code for writing dxf files with arcs, circles, and ellipses

Processing Development
1

I have seen a few questions about writing dxf files that contain arcs or circles. The processing dxf library treats these by breaking them down to lines which generates excessively long files. I recently ran across an old forum post where circles were generated but not arcs and the code was incomplete. I went back through the dxf documentation and found the needed information for creating arcs in dxf. Below is a modification of the example code from the old post, extending it to show how to create lines and arcs as well as circles. Page 86 of the autodesk dxf reference document discusses the format for ellipses, which I am sure can be treated in the same way. Points are discussed on page 123.
EDIT: Code for drawing an ellipse tacked on at the end.
This code does not use the dxf library and works in P2D.

String[] expDxf = {"0", "SECTION", "2","ENTITIES","0"};
 String fileName = "file2.dxf";
 
 float[] x = {10, 20, 30};
 float[] y = {10, 50, 100};
 float theta = 30;    // beginning of arc in degrees
 float phi = 160;     // end of arc

 float rad = 40;     // radius
 String layer = "0";

void dxfLine(float x0, float y0, float x1, float y1){
  int oldLen = expDxf.length;
  int newLen = (expDxf.length+16);
  expDxf = expand(expDxf, newLen );
   expDxf [oldLen] = "LINE";
  expDxf [oldLen+1] = "8";  // layer name
  expDxf [oldLen+2] = layer;
  expDxf [oldLen+3] = "10";   // x position of start
  expDxf [oldLen+4] = str(x0);
  expDxf [oldLen+5] = "20";   // y position of start
  expDxf [oldLen+6] = str(y0);
  expDxf [oldLen+7] = "30";   // z position of start
  expDxf [oldLen+8] = "0.0";   // z value is zero
    expDxf [oldLen+9] = "11";   // x position of end
  expDxf [oldLen+10] = str(x1);
  expDxf [oldLen+11] = "21";   // y position of end
  expDxf [oldLen+12] = str(y1);
  expDxf [oldLen+13] = "31";   // z position of end
  expDxf [oldLen+14] = "0.0";   // z value is zero
  expDxf [oldLen+15] = "0";
}


void dxfCircle(float x, float y, float rad){ // , String layer) {
  int oldLen = expDxf.length;
  int newLen = (expDxf.length+12);
  expDxf = expand(expDxf, newLen );
  expDxf [oldLen] = "CIRCLE";
  expDxf [oldLen+1] = "8";  // layer name
  expDxf [oldLen+2] = "0";
  expDxf [oldLen+3] = "10";   // x position of center
  expDxf [oldLen+4] = str(x);
  expDxf [oldLen+5] = "20";   // y position of center
  expDxf [oldLen+6] = str(y);
  expDxf [oldLen+7] = "30";   // z position of center
  expDxf [oldLen+8] = "0.0";
  expDxf [oldLen+9] = "40";     // radius
  expDxf [oldLen+10] = str(rad);
  expDxf [oldLen+11] = "0";
}

// note: theta and phi are the starting and ending angles of the arc

void dxfArc(float x, float y, float rad, float theta, float phi){
    int oldLen = expDxf.length;
  int newLen = (expDxf.length+16);
  expDxf = expand(expDxf, newLen );
  expDxf [oldLen] = "ARC";
  expDxf [oldLen+1] = "8";  // layer name
  expDxf [oldLen+2] = layer;
  expDxf [oldLen+3] = "10";   // x position of center
  expDxf [oldLen+4] = str(x);
  expDxf [oldLen+5] = "20";   // y position of center
  expDxf [oldLen+6] = str(y);
  expDxf [oldLen+7] = "30";   // z position of center
  expDxf [oldLen+8] = "0.0";
  expDxf [oldLen+9] = "40";     // radius
  expDxf [oldLen+10] = str(rad);
  expDxf [oldLen+11] = "50";     // sstarting angle
  expDxf [oldLen+12] = str(theta);
  expDxf [oldLen+13] = "51";     // endng angle
  expDxf [oldLen+14] = str(phi);
  expDxf [oldLen+15] = "0";
}

void dxfEnd() {
  expDxf = expand(expDxf, expDxf.length+3 );
  expDxf[expDxf.length-3] = "ENDSEC";
  expDxf[expDxf.length-2] = "0";
  expDxf[expDxf.length-1] = "EOF" ;
  saveStrings(fileName, expDxf);
}

void setup(){
size(100,100);
noLoop();
dxfLine(x[0],y[0],x[1],y[1]);
dxfCircle(x[0],y[0],rad);
dxfArc(x[1],y[1],rad*2,theta, phi);
dxfEnd();
}

EDIT: ok, here is a method for generating an ellipse:

////// x and y define the center of the ellipse, 
/////   endX and endY define the end of major axis, 
/////   ratio is the ratio of minor to major axis length
void dxfEllipse(float x, float y, float endX, float endY, float ratio){
  int oldLen = expDxf.length;
  int newLen = (expDxf.length+18);
  expDxf = expand(expDxf, newLen );
  expDxf [oldLen] = "ELLIPSE";
  expDxf [oldLen+1] = "8";  // layer name
  expDxf [oldLen+2] = layer;
  expDxf [oldLen+3] = "10";   // x position of center
  expDxf [oldLen+4] = str(x);
  expDxf [oldLen+5] = "20";   // y position of center
  expDxf [oldLen+6] = str(y);
  expDxf [oldLen+7] = "30";   // z position of center
  expDxf [oldLen+8] = "0.0";
  expDxf [oldLen+9] = "11";   // x position of end of major axis
  expDxf [oldLen+10] = str(endX);
  expDxf [oldLen+11] = "21";   // y 
  expDxf [oldLen+12] = str(endY);
  expDxf [oldLen+13] = "31";   // z 
  expDxf [oldLen+14] = "0.0";
  expDxf [oldLen+15] = "40";   // ratio of axis lengths
  expDxf [oldLen+16] = str(ratio);
  expDxf [oldLen+17] = "0";
}