Join Rob Garrott for an in-depth discussion in this video Part 2: Building a simulation in Houdini, part of Artists and Their Work: Conversations about Mograph, VFX, and Digital Art.
- Maybe we should take a look at some simulations, then. Do you think you can build a simulation for us? - Yeah. Yeah. - Talk while we're doing it. - Yeah, absolutely. - Let's do that then. - Let me just jump over to Houdini here. So I've actually got this brick wall set up here. Again, I was talking earlier about the idea that I had this fine art background. - Right. - For me a lot of art making is like building something and then tearing it apart, and then trying to build another thing out of the remains of what you just made.
One of the things, once I started learning Houdini, that appealed to me on the artist side, is that it's procedural, so you can build something and then change it, and you don't necessarily start from scratch, because you work in this procedural way that allows you to make changes in different parts of the software, and it will sort of propagate through the system that you've built. That really appealed to me. A super simple example here would be this brick wall, for instance.
By using this network that I've built, you can change the number of the bricks or the height of the bricks. These are simple little things, but what I found was when I was trying to make a cool shot, particularly where it's a simulation and it's physically based, so you don't have a hundred percent control over it, sometimes it was nice that I would run a simulation and go, "Oh, that should be two feet taller." Or, "That thing needs to break here instead of here." - It's a lot like setting up a stack of dominoes.
- Exactly. Exactly. You kind of know what it's going to do. - You hope. - And then it gets part way through and it misses one. You're like, "Ah! "Now I've got to set all that up again." Now I don't have to set it up again. - You can just click and go back to the beginning. - Exactly. Exactly. So, yeah, let's just turn this into a sim here. - I don't want to take it for granted of what a simulation is. Can you define a simulation for me? - Sure. Actually if I just set this up here real quickly I'll be able to maybe talk about it a bit.
Really a simulation with CG is, there's usually something called a solver, and that basically handles the math or the physics. But it really, literally is usually an extremely simplified version of reality. Calculating a real simulation is intensive. You need crazy computers and things people don't have. The idea is to try and make it look as real as possible while stripping out all the data that you don't actually need to make it look real enough that people believe it.
Which is kind of the fun thing actually about visual effects and animation that as long as it looks real enough that's all that really matters. - It just have to look good. - As long as nothing stands out and makes people go, "That's weird. It shouldn't do that." But in the basic sense, you just have objects, and they have some sort of properties like the weight or the size, and then there's just literally math equations run on it to say from this frame to frame, how far would it have moved if gravity operated on it, or whatever, which actually you can see here at the bottom, the gravity is played. - Oh, excellent, yeah.
- So I think actually if I play this right now. - (laughs) We got one. - Not much is probably going to happen there. Let me just add something to this so it will be a bit more interesting. I'll just add a ... We'll just use a sphere. It will be the easiest thing to do. Shrink it down. It has all the modelling stuff. Obviously, if I was doing a real project I would probably take some more time to make something a little nicer-looking than this.
But the idea is you model anything that you want really, - Sure. - Then use these tools to turn them into these dynamic objects, these things that have physical properties. Basically, I've just turned that sphere into an object here. You can actually see it plugged in. - I see. - Which is also another thing. As an artist, I like the idea that I can see all this stuff, that it's all connected and I can sort of understand how things are working.
- Right. - That always appealed to me, because I did like, again, the idea of taking stuff apart and seeing how it works and putting it together. This really gave me that feeling. When I first started learning, I would look at this, and I would have no idea how this worked at all. So then I would just say, "What happens if I delete this?" Then I would hit play and, "Okay, nothing works." So that's important, whatever that was. That was an important part. It was cool that I could do that, literally just destroy it and rebuild it. - Sure.
- And learn by sort of failing, basically. So let's see. Well, our sphere should probably do something more than just fall on the ground like that. What we can actually do is put, here are some of the physical properties that I talked about so you can see velocity, right? - If we put some velocity along the Z axis, which I'm pretty sure is going left to right here, - Right. - Our sphere, - Boom! Nice. - should sort of burst through there.
For me, this is what was magical, is seeing that happen. - Yeah, a very realistic movement. - Exactly. Then looking at this and going, "Well, where can I put the camera now "that will make this look cool" - Yeah. - Because it could be anywhere. - Yeah. - Maybe it would be neat to have them come right at the camera or something, roll past. - Right. Right. - It's all this weirdly technical stuff. But then instantly switches into this artistic thing. "Where can I put stuff? "How does this look? "How can I light this?" - I guess one of the things that is really awesome about having the illustration background, especially the storytelling things that you do with comic books, do you find the shot choices that you make are influenced by that? - Yeah, absolutely.
Oftentimes, if I know ahead of time what my project is going to be, I'll start by drawing it all. I'll start with basically like a storyboard. Then there's this interesting challenge of how can I make this physical simulation do what I drew? Because there's real physics in there, so I don't have total control over it. If I tweak it just slightly, or if I change the shape of this thing it'll bounce differently.
Little things like that. But yeah, I almost always start with a drawing and a storyboard, and then that gives me, because that's even faster. You can draw 10 pictures pretty quickly, and say, "Is that cool or not?" Maybe even take it into Aftereffects or Premier or something - And time it out. - and time it out. - Figure out, "Is that cool?" Because usually these demos, I don't work at an animation studio, so I've got 10 seconds, and that's it.
I have to show you something cool in 10 seconds. That's why planning it out like that, for me anyway, - It's critical. - Yeah, exactly. - It's such an important step in the process, and a lot of folks skip over it. But writing something down on paper gives it life. - It really does. Absolutely. - Maybe you could add a little bit of dust to this explosion and where it would go. I'd love to see that process. - Right now, this is just a pile of bricks, basically.
You can't really call it a wall because nothing's holding anything together. If we want to create dust, we probably want to do it so that when something breaks that's probably where the dust is going to come through. - Right. Right. - Unless the whole thing is just covered in dust, I guess. Maybe what I'll do is, I'll sort of glue this whole wall together, and that way, it won't just all come apart. It actually will break. - Wow. - It will break apart.
We can literally just glue it together. If I zoom in here you can see these - Oh, those are the connectors. - These red lines. That's actually the glue bonds - Wow. - between the pieces. - Connecting axis to axis? - It's like, the center of each object, basically, looks for the next object near it and connects it. - Excellent. It's really interesting as I watch you do this, there was a thought process you went through that was really interesting, asking yourself questions about the type of object that you were trying to create.
- Animation and visual effects is this really odd art form that has, you know, there's extreme high end amounts of art on one side, and then there's all this technical stuff on the other side. But in order for any of it to work, it has to meet somewhere in the middle. Otherwise, I would have to animate this, like hand, frame by frame, move these bricks. - Each brick, yeah. - Even just learning the software, most animation software in general, it's not complex, but it's technical.
You have to understand how the software works, how the rendering is going to work. It's this really cool mix of, you have to have great artists, but you also have to have great technology. - Software tends to be meaningless without a creative goal to motivate it. - Well, that's sort of how I got hired. - Yeah. - These guys, and they still do, the programmers, we always laugh about it. It's like a Taurus, it's always a Taurus. Or it's like a box and that's it. - That's all they've got.
- They're like, "Here's the new thing." And it's like, "It's another box." Then immediately you think, "Well, no." Why can't it be an ocean and a boat, instead of a box and a box. That's definitely the idea. I think I just ran this sim, and the glue is actually too strong. - That's pretty strong glue actually. - You can change the shoes. - I could use some glue like that a few days ago. - Let's see here. There we go. That's a good one. - Oh, nice, yeah.
- That sort of sticks together up here. - It really does. - Make it slightly stronger. - Yeah, that's kind of cool. - Excellent. It even stops the ball. - Yeah, exactly. This is actually what I was talking about with physical simulations you kind of know how it's going to work. - It's always unpredictable. - I would actually not have thought that it would do this, like fall down and tip over like that. That's pretty cool. So now we've got some glue, let's go ahead and some X to do that.
Actually, this is a neat side issue, I guess, is that this tool that does this, I guess I should play this so you can see what it does. - Oh, wow, look at that. I actually built this tool. - Oh, wow. - That's what's been fun for me, is that I knew this was a problem. This is something people are going to want to do. They're going to want to create this dust. Just like in my spare time at work, I just took it upon myself to try and solve the problem in Houdini.
Then Side Effects was nice enough to say, "That's cool. "Let's put that in there." That's a nice feature. - That's useful. - Yeah, exactly.
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