Object walk with trail (footprints)

Processing Coding Questions
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(The small check if it’s new doesn’t work)

Explanation

Instead of PVector (the in-built type to store a point with x,y) that we used previously we define a new type “Line” that stores 2 PVectors (line from point 1 to point 2). To define a type, we made a class “Line”.

To store a line in our list we just say

    listFootprints.add(new Line(new PVector(x1, y1), new PVector(x2, y2)));

As you can see we make a new line by passing 2 PVectors in it (that we make on the fly) and add the line to the list. (you have to read this from inside to outside: from x1,y1 to PVector, 2 PVectors needed to make a line, add the line to list)

  • The nice thing of using a class is that we can place a function “display()” inside a class to work with one line.

Sketch

ArrayList<Line> listFootprints = new ArrayList();

void setup() {
  size (700, 700);    // set the size of the window
  smooth();
  noCursor();   // hides mouse cursor
}

void draw() {
  background(255); // Draw a white background

  // draw FootPrints
  drawFootPrints();

  // show size of the list (for testing)
  text(listFootprints.size(), 17, 17);

  //Draw Zoog
  drawZoog(mouseX, mouseY);
}

// ---------------------------------------------------------------------------------

void drawZoog(float x, float y) {
  // draw Zoog

  // store formatting
  push();

  //Set ellipses and rect to CENTER mode
  ellipseMode(CENTER);
  rectMode(CENTER);
  //Draw Body
  stroke(0);
  fill(175);
  rect(x, y, 20, 100);
  //Draw Head
  stroke(0);
  fill(255);
  ellipse(x, y-30, 60, 60);
  //Draw Zoog's eyes
  fill(0);
  ellipse(x-18, y-30, 16, 32);
  ellipse(x+18, y-30, 16, 32);
  // Draw legs
  stroke(0);
  line(x+10, y+50, x+20, y+60);
  line(x-10, y+50, x-20, y+60);

  // store footprints (from legs position)
  if (mouseX>0 && mouseY>0) {   // if mouse is there
    storeFootprints(x+10, y+50, x+20, y+60);
    storeFootprints(x-10, y+50, x-20, y+60);
  }

  // restore formatting
  pop();
}

void storeFootprints( float x1, float y1,
  float x2, float y2) {
  // store the foot print

  // The first 3 times we store the foot print
  if (listFootprints.size()==0 || listFootprints.size()==1 || listFootprints.size()==2) {
    listFootprints.add(new Line(new PVector(x1, y1), new PVector(x2, y2)));
    return; // leave
  }//if

  // After the first time we check if the last position was the same,
  // we store the foot print only when it's new:
  // last position:
  if (  listFootprints.get(listFootprints.size()-2).pv1.x != x1 || listFootprints.get(listFootprints.size()-2).pv1.y != y1   )
    listFootprints.add(new Line(new PVector(x1, y1),
      new PVector(x2, y2)));
} //func

void drawFootPrints() {
  for (Line l1 : listFootprints) {
    noFill();
    l1.display();
  }//for
}//func

// ============================================================================

class Line {
  PVector pv1;
  PVector pv2;

  // constr
  Line(PVector pv1_, PVector pv2_) {
    pv1=pv1_.copy();
    pv2=pv2_.copy();
  }// constr

  void display() {
    line(pv1.x, pv1.y,
      pv2.x, pv2.y);
  }//method
  //
}//class
//
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