How to rotate a line in a circle (radar like), while also plotting distance reading points?

Eos2350

I am trying to rotate a line around in a circle that represents the direction a sensor is facing, while also plotting distance measurements. So I can't use background() in the draw function to clear the screen, because it erases the plotting of the distance readings. I've tried pggraphics and a few others ways, but can't seem to find a way to do it.

This is what I have right now:

void setup() {
   background(255,255,255);
   size(540, 540);
 }

 void draw() {
   translate(width/2, height/2); 
   ellipse(0,0,100,100);
   newX = x*cos(theta)- y*sin(theta);
   newY = x*sin(theta)+ y*cos(theta);

   theta = theta + PI/100;
   //pushMatrix();
   fill(255, 255);
   line(0, 0, newX, newY);
   rotate(theta);
   //popMatrix(); 
 }

I am new to Processing, and coding in general, but can anyone point me in the right direction on how to do this? Thanks

koogs

what are x and y on lines 9 and 10? you haven't defined them...

BUT, you don't need to - they are the radius of the ellipse in line 8 - replace them with 100.

delete line 16 - you don't need to rotate(), you are working out the rotation yourself in lines 9 and 10.

you need to define theta. do it at the top of the file.

Eos2350

koogs- I forgot to include the top of the file:int x = 1000; int y = -1000; float newX, newY; float theta; PGraphics pg;

I can get the line to rotate just fine, its just I can't figure out how to erase the previous line without calling background(). Do you know how I could do this? Possibly using a pushMatrix or pgGraphic?

Chrisir

just use background

Chrisir

I see

Chrisir

you don't do plotting of the distance readings yet, right?

Chrisir

maybe this can help you

storing all distance readings in an ArrayLIst and display from there....

;-)

// to store all distance readings
ArrayList<PVector> list = new ArrayList(); 


int x;
int y = -1000; 
float newX, newY;
float newX2, newY2;
float oldX, oldY;
float theta; 
PGraphics pg;


void setup() {
  background(255, 255, 255); // white 
  size(540, 540);
  frameRate(5);
}

void draw() {
  translate(width/2, height/2);

  stroke(0, 0, 243); 
  ellipse(0, 0, 100, 100);
  newX = x*cos(theta)- y*sin(theta);
  newY = x*sin(theta)+ y*cos(theta);


  float r1 = random(0.0, 120.0);

  // test distance readings (pseudo)
  newX2 = r1*cos(theta);
  newY2 = r1*sin(theta);
  list.add(new PVector(newX2, newY2)); // store 

  theta = theta + PI/100;
  //pushMatrix();

  // delete 
  strokeWeight(2);
  stroke(255);// white 
  line(0, 0, oldX, oldY);
  strokeWeight(1);



  /// draw
  stroke(0);
  line(0, 0, newX, newY);

  // display all distance readings
  for (PVector point : list) {
    stroke(255, 2, 2); // red 
    point(point.x, point.y);
  }

  oldX=newX;
  oldY=newY;
  // rotate(theta);
  //popMatrix();
}