import java.util.Vector;import javax.media.j3d.*;import javax.vecmath.*;import com.sun.j3d.utils.geometry.*;/** * This class walks through an L-system rule, as a Logo turtle would. * The turtle draws line segments (cylinders) behind it. * (called by: Lsystem.java, Interpreter.java) * * @author: Scott Teresi, April 1999, www.teresi.us */public class Interpreter {  State s = new State();  Vector stateStack = new Vector();  Appearance branchApp = new Appearance();  Appearance leafApp = new Appearance();  int depth;  String rule;  int cylEdges = 3;  double cylRadius = 0.1;  double mult = 0.01;  boolean debug = false;;  public Interpreter () {    // set the default Appearances    Material mat1 = new Material();    mat1.setDiffuseColor(.9f, .2f, .05f);    mat1.setAmbientColor(.18f, .05f, 0f);    branchApp.setMaterial(mat1);    Material mat2 = new Material();    mat2.setDiffuseColor(0f, .7f, .05f);    mat2.setAmbientColor(0f, .3f, 0f);    leafApp.setMaterial(mat2);  }  public void setState (State state) {    s = state;  }  public void setAppearance (Appearance app1, Appearance app2) {    branchApp = app1;    leafApp = app2;  }  public void initDraw (double rad, double m, int edges, boolean dbg) {    cylRadius = rad;    mult = m;    cylEdges = edges;    debug = dbg;  }  public BranchGroup execute(int d, String r) {    depth = d;    rule = r;    BranchGroup bg = new BranchGroup();    if (depth == 0)      return bg;    if (debug) {      for (int i = 0; i < (8-depth); i ++)	System.out.print("  ");      System.out.println("Interpreting: " + rule);    }    int i = 0;    while (i < rule.length()) {      // System.out.println(rule.charAt(i) + "  " + new Point3f(s.curPos) +      //		 "  " + s.angle);      switch (rule.charAt(i)) {        case ' ':        case '=':	  break;        case '+':	  // turn the cursor left	  if (!s.swapDirections)	    s.angle += s.angleInc;   // turn left	  else	    s.angle -= s.angleInc;   // turn right	  if (s.angle > 360.0)	    s.angle -= 360.0;	  if (s.angle < -360.0)	    s.angle += 360.0;	  break;        case '-':	  // turn the cursor right	  if (!s.swapDirections)	    s.angle -= s.angleInc;   // turn right	  else	    s.angle += s.angleInc;   // turn left	  if (s.angle > 360.0)	    s.angle -= 360.0;	  if (s.angle < -360.0)	    s.angle += 360.0;	  break;        case '!':	  // swap directions of all following cursor turns	  s.swapDirections = !s.swapDirections;	  break;        case 'f':	  // move forward one line length (actually DRAW something!)	  double x = s.lineLength*Math.cos(Math.PI * s.angle/180.0) +	             s.curPos.x;	  double y = s.lineLength * Math.sin(Math.PI * s.angle/180.0) +	             s.curPos.y;	  double z = s.curPos.z;	  CylinderCreator cylinder = new CylinderCreator();	  cylinder.setResolution(cylEdges);	  Appearance app;	  if (depth > 1)	    app = branchApp;	  else	    app = leafApp;	  // make a branch	  bg.addChild(cylinder.create(s.curPos, new Point3d(x, y, z),	       cylRadius + mult * s.lineLength, app));	  // cap the end of the branch	  Transform3D transMatrix = new Transform3D();	  transMatrix.setTranslation(new Vector3d(x, y, z));	  TransformGroup tg = new TransformGroup(transMatrix);	  Sphere sphere = new Sphere((float) (cylRadius + mult*s.lineLength),				     Sphere.GENERATE_NORMALS, app);	  tg.addChild(sphere);	  bg.addChild(tg);	  s.curPos = new Point3d(x, y, z);	  break;        case '@':	  // scale the line length up or down	  i = readScaleValue(i+1);	  break;        case 'z':        case 'y':        case 'x':        case 'w':        case 'v':	  // interpret the rule for the variable encountered	  Interpreter interpreter = new Interpreter();	  interpreter.setState(s);	  interpreter.setAppearance(branchApp, leafApp);	  interpreter.initDraw (cylRadius, mult, cylEdges, debug);	  bg.addChild(interpreter.execute(depth - 1,					  Rules.getRule(rule.charAt(i))));	  break;        case '[':	  // remember the current graphics state	  stateStack.addElement(new State(s));	  break;        case ']':	  // recall the previous graphics state	  if (stateStack.size() > 0)	    s = (State) stateStack.remove(stateStack.size() - 1);	  else	    System.out.println("Missing ] in line: " + rule);	  break;        default:	  break;      }      i ++;    }    bg.compile();    return bg;  }  int readScaleValue(int i) {    StringBuffer valString = new StringBuffer();    while (i < rule.length()) {      switch (rule.charAt(i)) {        case '.':        case '1':        case '2':        case '3':        case '4':        case '5':        case '6':        case '7':        case '8':        case '9':        case '0':	  valString.append(rule.charAt(i));	  break;        default:	  double scale = 0;	  try {	    scale = (new Double(valString.toString())).doubleValue();	  } catch (Exception ex) {	    System.out.println("Bad line length scale value, position " + i);	    System.out.println("Line: " + rule);	    System.exit(1);	  }	  s.lineLength *= scale;	  // if (debug)	  //  System.out.println("new line length: " + s.lineLength);	  return i-1;      }      i ++;    }    return i;  }}