Question

I’m trying to write a simple game in Java that uses Processing to render graphics. However, I’m having trouble rendering any changes using updatePixels(). I can successfully set the background color and draw basic 2d shapes, but I get nothing from editing the pixels[] variable, or from using set(x, y, color).

This is my (abridged) code:

import processing.core.*;

public class GameController extends PApplet {
  private int width, height;

  private final static String RENDER_MODE = PConstants.P2D; //JAVA2D;

  public GameController(int width, int height) {
    this.width = width;
    this.height = height - this.getBounds().y;
  }

  @Override
  public void setup() {
    this.size(this.width, this.height, RENDER_MODE);
    this.background(0);
  }

  @Override
  public void draw() {
    this.ellipse(50, 50, 100, 10);

    this.loadPixels();
    for (int p : this.pixels) {
      p = this.color(255, 0, 0);
    }
    this.updatePixels();
  }
}

When I init() this class, I get a white ellipse on a black screen, not a screen of red pixels (which is what I’m expecting).
The pixels[] array is definitely there, as I’ve printed it out, and I’m getting no errors.
What am I doing wrong?

Answer 1

This line:

p = this.color(255, 0, 0);

only changes the local variable p, which contained a copy if the pixel value.

What you want is to modify the values inside the pixels array, as in:

for (int i = 0 ; i < pixels.length ; i++) {
    pixels[i] = color(255, 0, 0);
}