js实现 穿越星空效果图

【实例截图】

【核心代码】

window.requestAnimFrame = (function() {
  return window.requestAnimationFrame
})();
var canvas = document.getElementById("space");
var c = canvas.getContext("2d");

var numStars = 1900;
var radius = '0.'   Math.floor(Math.random() * 9)   1;
var focalLength = canvas.width * 2;
var warp = 0;
var centerX, centerY;

var stars = [],
star;
var i;

var animate = true;

initializeStars();

function executeFrame() {

  if (animate) requestAnimFrame(executeFrame);
  moveStars();
  drawStars();
}

function initializeStars() {
  centerX = canvas.width / 2;
  centerY = canvas.height / 2;

  stars = [];
  for (i = 0; i < numStars; i  ) {
    star = {
      x: Math.random() * canvas.width,
      y: Math.random() * canvas.height,
      z: Math.random() * canvas.width,
      o: '0.'   Math.floor(Math.random() * 99)   1
    };
    stars.push(star);
  }
}

function moveStars() {
  for (i = 0; i < numStars; i  ) {
    star = stars[i];
    star.z--;

    if (star.z <= 0) {
      star.z = canvas.width;
    }
  }
}

function drawStars() {
  var pixelX, pixelY, pixelRadius;

  if (canvas.width != window.innerWidth || canvas.width != window.innerWidth) {
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    initializeStars();
  }
  if (warp == 0) {
    c.fillStyle = "rgba(0,10,20,1)";
    c.fillRect(0, 0, canvas.width, canvas.height);
  }
  c.fillStyle = "rgba(255, 255, 255, "   radius   ")";
  for (i = 0; i < numStars; i  ) {
    star = stars[i];

    pixelX = (star.x - centerX) * (focalLength / star.z);
    pixelX  = centerX;
    pixelY = (star.y - centerY) * (focalLength / star.z);
    pixelY  = centerY;
    pixelRadius = 1 * (focalLength / star.z);

    c.fillRect(pixelX, pixelY, pixelRadius, pixelRadius);
    c.fillStyle = "rgba(255, 255, 255, "   star.o   ")";
  }
}

executeFrame();