cdf/src/old/starfield.js

A library for creating oldschool demo-like animations with JavaScript

(function (global) {
  var lib = global.cdf || {};
  
  var starfield3D = lib.starfield3D = function(dest, nb, speed, w, h, centx, centy, color, ratio, offsetx, offsety) {
    this.dest = dest;
    this.test = true;
    this.n = nb || 300;
    this.star = new Array(this.n);
    this.w = typeof w !== 'Number' ? dest.w : w;
    this.h = typeof h !== 'Number' ? dest.h : h;
    this.x = 0;
    this.y = 0;
    this.z = 0;
    this.offsetx = offsetx || 0;
    this.offsety = offsety || 0;
    this.centx = centx;
    this.centy = centy;
    this.color = color || '#fff';
    this.star_speed = speed || 1;
    this.star_ratio = ratio || 100;
    this.star_color_ratio = 0;
    this.x = Math.round(this.w / 2);
    this.y = Math.round(this.h / 2);
    this.z = (this.w + this.h) / 2;
    this.star_color_ratio = 1 / this.z;
    this.cursor_x = this.x;
    this.cursor_y = this.y;

    for (var i = 0; i < this.n; i++) {
      this.star[i] = [
        Math.random() * this.w * 2 - this.x * 2,
        Math.random() * this.h * 2 - this.y * 2,
        Math.round(Math.random() * this.z),
        0,
        0
      ];
    }

    return this;

  }
  
  starfield3D.prototype.draw = function () {
      this.dest.ctx.save();
      
      this.dest.ctx.globalAlpha = 1;
      this.dest.ctx.strokeStyle = this.color;

      for (var i = 0; i < this.n; i++) {
        this.test = true;
        this.star_x_save = this.star[i][3];
        this.star_y_save = this.star[i][4];
        this.star[i][0] += (this.centx - this.x) >> 4;
        if (this.star[i][0] > this.x << 1) {
          this.star[i][0] -= this.w << 1;
          this.test = false;
        }
        if (this.star[i][0] < -this.x << 1) {
          this.star[i][0] += this.w << 1;
          this.test = false;
        }
        this.star[i][1] += (this.centy - this.y) >> 4;
        if (this.star[i][1] > this.y << 1) {
          this.star[i][1] -= this.h << 1;
          this.test = false;
        }
        if (this.star[i][1] < -this.y << 1) {
          this.star[i][1] += this.h << 1;
          this.test = false;
        }
        this.star[i][2] -= this.star_speed;
        if (this.star[i][2] > this.z) {
          this.star[i][2] -= this.z;
          this.test = false;
        }
        if (this.star[i][2] < 0) {
          this.star[i][2] += this.z;
          this.test = false;
        }
        this.star[i][3] = this.x + (this.star[i][0] / this.star[i][2]) * this.star_ratio;
        this.star[i][4] = this.y + (this.star[i][1] / this.star[i][2]) * this.star_ratio;
        if (this.star_x_save > 0 && this.star_x_save < this.w && this.star_y_save > 0 && this.star_y_save < this.h && this.test) {
          this.dest.ctx.lineWidth = (1 - this.star_color_ratio * this.star[i][2]) * 2;
          this.dest.ctx.beginPath();
          this.dest.ctx.moveTo(this.star_x_save + this.offsetx, this.star_y_save + this.offsety);
          this.dest.ctx.lineTo(this.star[i][3] + this.offsetx, this.star[i][4] + this.offsety);
          this.dest.ctx.stroke();
          this.dest.ctx.closePath();
        }
      }
      this.dest.ctx.restore();
    }

  var Starfield3D = lib.Starfield3D = function(star_number){
    this.star_number = star_number;
  }

  Starfield3D.prototype = {
    __calculateNewPositions:function(){
    },
    draw:function(target_canvas, x, y, w, h){
    }
  }

  var starfield2D_dot = lib.starfield2D_dot = function(dst, params) {
    this.dst = dst;
    this.stars = new Array();
    var t = 0;

    for (var i = 0; i < params.length; i++) {
      for (var j = 0; j < params[i].nb; j++) {
        this.stars[t] = {
          x: Math.random() * this.dst.canvas.width,
          y: Math.random() * this.dst.canvas.height,
          speedx: params[i].speedx,
          speedy: params[i].speedy,
          color: params[i].color,
          size: params[i].size
        };
        t++;
      }
    }

    this.draw = function () {
      for (var i = 0; i < this.stars.length; i++) {
        this.dst.plot(this.stars[i].x, this.stars[i].y, this.stars[i].size, this.stars[i].color);
        this.stars[i].x += this.stars[i].speedx;
        this.stars[i].y += this.stars[i].speedy;
        if (this.stars[i].x > this.dst.canvas.width) this.stars[i].x = 0;
        if (this.stars[i].x < 0) this.stars[i].x = this.dst.canvas.width;
        if (this.stars[i].y > this.dst.canvas.height) this.stars[i].y = 0;
        if (this.stars[i].y < 0) this.stars[i].y = this.dst.canvas.height;
      }
    }
  };

  var starfield2D_img = lib.starfield2D_img = function(dst, img, params) {
    this.dst = dst;
    this.stars = new Array();
    this.img = img;
    var t = 0;

    for (var i = 0; i < params.length; i++) {
      for (var j = 0; j < params[i].nb; j++) {
        this.stars[t] = {
          x: Math.random() * this.dst.canvas.width,
          y: Math.random() * this.dst.canvas.height,
          speedx: params[i].speedx,
          speedy: params[i].speedy,
          params: params[i].params
        };
        t++;
      }
    }

    this.draw = function () {
      for (var i = 0; i < this.stars.length; i++) {
        this.dst.ctx.drawImage(this.img[this.stars[i].params].img, this.stars[i].x, this.stars[i].y);
        this.stars[i].x += this.stars[i].speedx;
        this.stars[i].y += this.stars[i].speedy;
        if (this.stars[i].x > this.dst.canvas.width) this.stars[i].x = 0 - this.img[this.stars[i].params].img.width;
        if (this.stars[i].x < 0 - this.img[this.stars[i].params].img.width) this.stars[i].x = this.dst.canvas.width;
        if (this.stars[i].y > this.dst.canvas.height) this.stars[i].y = 0 - this.img[this.stars[i].params].img.height;
        if (this.stars[i].y < 0 - this.img[this.stars[i].params].img.height) this.stars[i].y = this.dst.canvas.height;
      }
    }

  };

  if(typeof module!=='undefined'&& module.exports){module.exports=lib;}else{global.cdf=lib;}
})(window);