Yan Zhao

2013年11月22日星期五

VIZA626 Generative Art--- Final Animation

For my final project. I want to continue polish my second project, the growing tree, to make it into a complete short animation. I kinda of changing my mind that I want the tree to grow out of flower instead of leaves, because that is more aesthetically appealing to me :)

The conceptual and aesthetic aspect of my final project is similar to my project 2. So here, I will focus on the technical challenges I have come up with in this project.

1. how to replace a simple leaf geometry with a complicated flower geometry.
I build the cherry blossom model using procedure modeling technique in Houdini. The network is showing below. This flower consists of two separate parts: pistil and petal.

For the flower petal. I first cut off curve node, use skin node to form a mesh, then apply twist node onto that mesh. The advantage of making flower in this way compared to just import a OBJ file is that: we can control the twist amount in our L-system to make procedure animation. Here is an example:

Twist strength set to 100:(flower bud)

Twist strength set to 50:(fully open)

2. how to control the procedure animation of flowers
In the L-system documentation, I found an interesting function, "stamp". In Houdini we know we can set a stamp value in copy node and the reference that value in the network, so in that way, we can make a slightly difference to each of copied object . L system support up to 3 stamp variables, we can use that variable to track the generation number of each flower and make them open at proper time.

Turtle codes I wrote in L-System:

3. rendering issue
Well, I turned on subsurface scattering, and set up like 15 lights? （= =） in shot in order to get a good rendering result.

Lots people ask me why the flower opens from the tip of branch to the root , the theory is: the further a flower is away from main truck, the easier it is to absorb solar energy.

Here is some test video I current got:

combined with the render result I had before：

2013年10月9日星期三

VIZA626 Generative Art--- Project 3: Fractal Clouds

Conceptual Aspect:
Clouds have distinctive shape, that is due to the fractal nature of cloud. Fractals are geometrical entities that have no intrinsic length scale. They are self-similar, that is they repeat themselves at any scale you pick. I am going to use the fractal tool in Houdini for the creation of volumetric cloud and terrain.

Technical Aspect:

1.The first technical challenge is to change a uniform volume into a cloud which has a density drop down from center to the edge. To solve this problem, I mapped a 2D image which is red in the middle and gradually change to black radically.

2.Make cloud look

Cloud has distinctive shape which is actually fractal. But at first I want to try other method rather than fractal to mimic cloud. I used turbulent noise to change volume density field. The following picture is network graph:

The following is the test sample that I got from the method I mentioned above:

Aesthetic Aspect:
The following is a playblast from a flying over camera angle. I didn't render them out because it kinda of too time consuming:

2013年9月23日星期一

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!

2013年9月2日星期一

VIZA626 Generative Art --- Project 1: Color Cell

Conceptual:

The idea of this project comes from cell propagation. In biology laboratory, we can often see the process of cell propagation in the culture dish through microscope. These living cell will try their best to absorb nutritions from nearby space. In order to achieve that, they will push themselves away from other cells to get enough space. This program is aimed to emulate that kind of behavior.

In this program, each cell has a color value on it, and they try to keep themselves from other cells in order to get enough space and nutrition to grow. On the other hand, each of these cells have several antennas around it, reaching outside, trying to find other cell. Once its antenna reaches those from other cell, a new cell will be born, with the color from both of its parents.

Behaviors driven by "Chance Operations":
Almost every change in this program is made by chance. For example, the color of each cell, the number of antennas of each cell, the speed of antennas rotation are all randomly set. Not to mention the result is even more unpredictable. We can not foresee where the next cell will be born. What will happen to the whole structure. Some cell will be pushed to the boundary and die, some will thrive and be dominated in color pattern.