I think in this work ... I just draw semen.
As the number of layers increases,
There are also a lot of seminal layers.
As a result, the working time becomes longer.
I have to solve this problem ... I do not know the solution.
GIF download link
https://drive.google.com/uc?export=download&id=0B1nS0o4r4HsUUVhrekZFS18tY2s