html5+canvas绘制抽象液体流动火焰动画特效

代码片段：

function draw() {

canvas.width = window.innerWidth;
canvas.height = window.innerHeight;

  if(animate && circle){
    t = (t+0.1)%(TWO_PI);
    x_new = Math.round(width/2 + width/4* Math.cos(t));
    y_new = Math.round(height/2 + height/4* Math.sin(t));
    disturbLine(x_new, y_new);

    x_old = x_new;
    y_old = y_new;
  }

  vel_step(u_, v_, u_old_, v_old_, visc_, dt_); 
  dens_step(dens_, dens_old_, u_, v_, diff_, dt_); 
  draw_texture();
  ctx_2.putImageData(plot_rgba, 0, 0);
  //ctx.drawImage(canvas_2,0,0,width,height,0,0,canvas.width,canvas.height);
ctx.drawImage(canvas_2,0,0,width,height,window.innerWidth/2-hwidth, window.innerHeight/2-hheight, canvas_2.width, canvas_2.height);
  window.requestAnimationFrame(draw);
}
draw();