多线程画树,在多线程的同步与异步中，线程互相不干扰出错，画出的树-Multi-threaded draw trees, many at the synchronous and asynchronous threads, the threads do not interfere with each other is wrong and draw the tree

一个LS文法系统,用分形技术生成一排树,模拟自然景观,参数由自己设置,-A LS grammar system, using fractal technique to generate a row of trees, simulate the natural landscape, parameters set by myself,