Get data from Arduino and display it in a radar-like screen from Processing.

radar.java

/* 
  Radar Screen Visualization for HC-SR04 + Servo
  Uses serial data from Arduino in format "angle,distance."
  Displays radar grid, sweeping beam, and obstacle points.
*/

import processing.serial.*;
Serial arduinoPort;

float radius = 350;
int radarRange = 300;
int degree = 0;
int distance = 0;
int[] distances = new int[181];

void setup() {
  size(800, 600);
  arduinoPort = new Serial(this, Serial.list()[0], 9600);;  // adjust to your port
  arduinoPort.bufferUntil('.');
  smooth();
}

void draw() {
  background(0);
  drawRadarGrid();
  drawSweep();
  drawDetectedPoints();
}

// Draw radar circles and angle lines
void drawRadarGrid() {
  translate(width/2, height - 50);
  noFill();
  stroke(0, 255, 0);
  strokeWeight(1);

  for (int r = 0; r <= radarRange; r += 50) {
    ellipse(0, 0, r*2, r*2);
  }

  for (int a = 0; a <= 180; a += 30) {
    float x = cos(radians(a)) * radarRange;
    float y = -sin(radians(a)) * radarRange;
    line(0, 0, x, y);
  }
}

// Draw sweeping beam from center
void drawSweep() {
  stroke(0, 255, 0);
  for (int i = 0; i < 60; i += 2) {
    stroke(0, map(i, 0, 60, 255, 0), 0);
    float x = cos(radians(degree - i)) * radarRange;
    float y = -sin(radians(degree - i)) * radarRange;
    line(0, 0, x, y);
  }
}

// Draw detected obstacle dots
void drawDetectedPoints() {
  for (int i = 0; i < 180; i++) {
    int d = distances[i];
    if (d > 0 && d < radarRange) {
      float x = cos(radians(i)) * d;
      float y = -sin(radians(i)) * d;
      stroke(0, 255, 0);
      fill(0, 255, 0);
      ellipse(x, y, 5, 5);
    }
  }
}

// Read serial input: "angle,distance."
void serialEvent(Serial port) {
  String data = port.readStringUntil('.');
  if (data != null) {
    data = trim(data);
    data = data.replace(".", "");
    String[] parts = split(data, ',');
    if (parts.length == 2) {
      degree = int(parts[0]);
      distance = int(parts[1]);
      if (degree >= 0 && degree < 180) {
        distances[degree] = distance;
      }
    }
  }
}