VIZA626 Generative Art--- Project 2: Growing Tree

Conceptual Aspect:

The conceptual aspect of this project is fairly straightforward . My first inspiration comes from a short film by Bruce Branit, "World Builder".  That film tells a story that a man builds a world using virtual reality tool for the women he loves. There is one shot in that film that the man shapes a tree in the center of a square with a virtual panel. Audience can see the growth process of the virtual tree in real time.

Another reference is a time lapse video captures oak tree grows from an acorn to 8 month old.

I use L-system in Houdini and to do this project.  With proper light , music and swaying movement of the branches to show the transition of four seasons. The final piece will be a short animation, shows the process that a seedgradually grows into a large tree. 

The technique chanllege of of this projects are 2 issues:

1. how to animate the growth of the tree truck.

•     As we know, the tree truck will become wider and wider in radius as it grows. To solve this problem, I create an attribute in houdini to keep track with the distance of certain point on L-System to its root. I then transfer this attribute to the Polywire SOP which is responsible to create geometrical mesh along L-system. So as it grows , the further point is from the root, the narrower it will be in radius, the following is the network graph I implement this function for the root growth:

• The following is the network graph of attribute creation process as I mentioned before:

2. how to control the growth of L-system

• As we know, most of L-system grow in certain pattern as we preset. Here is the code I wrote in houdini in order to define the rule:
  
• But the problem is , if we just let L-System grows without any interference , this processing will not look very natural. For example, at some point, the tree will stop grow as it runs to rule 2, but when it comes to rules 3,  the leaves will spawn out all of a sudden. To solve this problem, I import noise into L-System using chop network(build-in network in houdini to control animation), so it looks fairly natural now. The following is the noise node network:
  

Here is some pre-render result, for the final piece, I will still need to put texture on to tree trunks and leaves, enjoy!