jasonfugh.com: The Blog

Finally another update. October was a little rough. Had a lot of stuff going on, sick for 2 weeks, some freelance stuff and ran into a problem with the rig and procedurally animating it. Anyways I hope to finish this before Thanksgiving, so I can start some python and tool building. Or maybe a demolition fx.


So since the last post I had to re work the rig for the fish. I was getting a lot of deformation I didn't want, plus I wasn't getting the control I needed. Having a background in character animation help with this part of the shot a bit, but without a great character rig and controls I wasn't able to get the motion I wanted, so I decided to go at it procedurally. First I created a line, and then used CHOPs to animate it. After editing and tweaking the CHOP Network so that the curve would move in a wave form, I used Houdini's rigging feature Follow Curve, which used the points to layout the bone structure. After that I just had to capture and edit the captured geometry. This was my 1st attempt to use CHOPs, and I'm definitely going to continue to use it, very powerful tool. (Thanks goes out to Andy N., for pointing me in the right direction, great tutorial and example file.) The next step was getting the cycled fish to actually move, instead of staying in place.

Normally I would just animate the character (in this case the fish) moving across the screen as I animated the movement of the character. However, since the original rig didn't workout I decide to continue animating it procedurally, through the new Motion FX feature "Lag". This feature is very simple you select the object you want to "lag behind" and the object you want it to "follow." In this case I drew out a curve and applied a sphere to follow along the curve or "the path". Next selected the fish to lag behind the sphere, and there you have it. The fish looks as though its swimming along with the sphere. Right now the motion isn't exactly how I want it, but I'm going to be editing the curve and some of the expressions a little later when I bring it all together.

As usual, here's an example vido of the actual test and breakdown. If anyone's thinking about breaking into Houdini, CHOP's is one of the things I recommend you learn (after getting the basics down). It's very powerful and you can tweak any of your animations, fx and simulations with it, and it will make for a better shot. Up next I should be posting some tweak I've made on my ink effect R&D stuff, as well as some shaders. And hopefully soon a final animation/simulation for you to view. Please feel free to leave any comments, suggestion or critiques.

I found a free model of this koi fish and I finished rigging it today. still some small skinning and paint weight issues, but nothing too serious. I'm going to attempt to animate the model procedurally by using the new feature in houdini called "Motion FX." I want to create a cycle where the fish swims slow to fast and back to a slower pace. The plan is to have a single particle follow a curve and instance the fish model onto that particle. Another possibility is to have a second object follow the curve and then use motion fx again to allow the fish model to follow that object. Here's a couple of screen shots so you can see the rig and model, also there's an example of the fish out lined in particles (since you won't actually see the model in great detail in the animation).

This post is just to show the volume and movement of the fluid smoke (the ink). This took several hours to simulate, so I found a quicker and easier way to get this effect with low resolution fluids. That will be in the next post, also working on the fish model (or trying to find a free model to use) and animation. Anyways the next post should be this weekend with new volume test, advected particles test and soome actual render tests. Let me know what you think about the video.


Here's the link for my reference.
http://www.pond5.com/index.php?page=search&p=0&q=ink+water+fluid&advs=

In this entry I will breakdown how I got the motion for the ink falling and sinking down into water. I will also have a video example of the motion and some network screen shots for you to view.

Ink Motion .01: Fluids
This is actually a very basic smoke set up. First started out with a smoke object and container. Inside the DOP Network I added a Gas Vorticle and Recycle nodes, where I added about 60,000 vorticles. Then inside the smoke object and solver nodes I adjusted the attributes, changing the uniform division to 150 and adjusting the bouyancy direction and lift. As I said this is a very basic set up. By the next post this might be more complexed or not even used.

Ink Motion 02. Particle Controlled Fluids:
Unlike the previous set up, this one is a little more complex. Instead of have a static RBD object emit the smoke, I have a POP Network controlling the smokes activation, so when ever a particle enters the container smoke is emitted. Here's a more detailed breakdown.

The idea behind this project was based on 2 separate ideas/videos. Particles morphing into an animated object and ink dropping into water. The final animation will be of ink falling slowly down and building up at the bottom, and then having some of the ink morph into a fish swimming away.

Week 1:

To get the exact motion I'm looking for, I've decided to use Fluid Smoke Dynamics. Right now I am using a smoke object to emit the fluids. Originally, I tried to use particles or Rigid Body Objects (RBD) to emit and control the smoke. By having the emitted particles controlling the fluids, I wasn't able to get the motion of ink in water; however, this is still an option I'm looking into using. The RBD Object worked, but the smoke wasn't emitting the way I needed it to; plus the smoke was only emitting from the bottom (need it to emit from the top and build up at the bottom), and having 2 simulations was taking too long to sim out. Here are some examples I'm using for the FX:

http://tinyurl.com/m39nzq
http://tinyurl.com/llbzuw

The motion of the ink still needs some more work, but here is what I have so far. The video below is the progress I have with the motion of the fluid (shown through denisty and temperature). Please feel free to leave any comments or suggests.




The next step will be to bake the simulation out as a 3D volume, too see if the motion as a volume is where I want it. Once that is done then I will add an RBD object and advect the fluid into particles. Hoping to add another update in a few days or sometime this week, with a test render of the smoke and a test video to see how the smoke reacts to the RBD Object going through the it. Once again please feel free to leave comments.

---fughfx