Add example Julia set (#106)

examples/julia.rs

@@ -0,0 +1,73 @@
+extern crate minifb;
+
+use minifb::{Window, Key, WindowOptions};
+
+const WIDTH: usize = 600;
+const HEIGHT: usize = 600;
+const FRACTAL_DEPTH: u32 = 64;
+const GENERATION_INFINITY: f64 = 16.;
+
+fn main() {
+  let mut buffer: Vec<u32> = vec![0; WIDTH * HEIGHT];
+
+  let mut window = match Window::new("Fractal - ESC to exit", WIDTH, HEIGHT, WindowOptions::default()) {
+    Ok(win) => win,
+    Err(err) => {
+      println!("Unable to create window {}", err);
+      return;
+    }
+  };
+
+  let range = 2.0;
+  let x_min = 0. - range;
+  let y_min = 0. - range;
+
+  let x_max = 0. + range;
+  let y_max = 0. + range;
+
+  let mut angle: f64 = 0.0;
+
+  while window.is_open() && !window.is_key_down(Key::Escape) {
+
+    for i in 0..buffer.len() {
+      let mut real = map((i % WIDTH) as f64, 0., WIDTH as f64, x_min , x_max);
+      let mut imag = map((i / HEIGHT) as f64, 0., HEIGHT as f64, y_min, y_max);
+
+
+      let mut n = 0;
+
+      while n < FRACTAL_DEPTH {
+        let re = real.powf(2.) - imag.powf(2.);
+        let im = 2. * real * imag;
+
+        real = re + angle.cos();
+        imag = im + angle.sin();
+
+        if (real + imag).abs() > GENERATION_INFINITY {
+          break;  // Leave when achieve infinity
+        }
+        n += 1;
+      }
+
+      buffer[i] = fill(n);
+    }
+
+    angle += 0.1;
+
+    // We unwrap here as we want this code to exit if it fails
+    window.update_with_buffer(&buffer).unwrap();
+  }
+}
+
+
+fn map (val: f64, start1: f64, stop1: f64, start2: f64, stop2:f64) -> f64 {
+  start2 + (stop2 - start2) * ((val - start1) / (stop1 - start1))
+}
+
+fn fill (n: u32) -> u32 {
+  if FRACTAL_DEPTH == n {
+    return 0x00;
+  } else {
+    return n * 32 % 255;
+  }
+}