4/26 Swimming Creatures and Soft Body Locomotion

This day we looked at several papers regarding swimming creatures. I thought the idea of modeling both the forces of water on the characters as well as the characters on the water makes sense - there's always two sides to every interaction, and I feel like it might not look correct if you don't model that. The papers that didn't do that didn't have such great results. The characters looked like there was no resistance working against them when they were swimming, like they were just doing the motions in air.

We also looked at a paper on soft body locomotion - characters that bend and stretch and have no skeleton. I thought the way they modeled the muscles in the characters was interesting, but could potentially be limiting. They had good results some of the time, but other examples, such as jumping and rolling, looked extremely bizarre. The motions that were good were really good, but the motions that were bad were really bad. I wonder if that would be solved by adding one more type of muscle, since they only had three: longitudinal, radial, and helical. I don't know what it would be, though.

4/24 Real-Time Deformation

I thought this paper was pretty cool, but I was unsure what type of materials they were trying to create. I thought most of the examples looked fairly realistic, but I was thinking about what objects in real life behave the way those did and I couldn't come up with any. I thought some of them looked a bit like Jello, but if you dropped Jello like those objects were dropped, the Jello would probably break. I also thought about those sticky hand toys:

They seemed a bit like that, but they weren't sticky. I kept thinking and I couldn't come up with any real world examples of objects that behave the way the simulated ones did. Even so, I still found the simulated ones to be convincing. How does that work? I suppose as long as they're physically plausible, they should be believable, but at the same time I think we find things believable if they are similar to things we've seen before. Something to think about.

4/17 Yarn-Based Cloth

This paper immediately caught my attention because I love to knit. Because of that, I understood more than anyone else in the class how yarn behaves, which also, I think, made me more critical. Overall I think their results were pretty good, but I was very disappointed that they didn't make distinctions between different types of yarn or needles. Fingering yarn is different from sock yarn is different from worsted yarn is different from chunky yarn. Wool is different from cotton is different from polyester is different from hemp is different from bamboo. All of these are different with different size needles. The first paper didn't address this at all, it seemed, and the later ones had examples with different yarns but didn't say what they were! As I said in class, the rectangle falling over the ball would be great if it were supposed to be fingering yarn on size 2 or 3 needles, but if that's supposed to be a worsted weight throw blanket it looks way to thin and light. I thought they had pretty great results, but they really needed to give their examples some context.

4/12 Upsampling for Cloth Simulation

I thought this paper was really cool - simplifying cloth simulation so it still looks somewhat believable but doesn't take so long. In discussion in class, I think we were a little bit to critical. No, it doesn't look perfect, so for a movie you're more than welcome to dislike it. But I definitely think if this showed up in a video game, people would be amazed by how great the clothing looks, which is the entire point of the simulation. I definitely think it needs some work, such as fixing the problem of it folding in the same places over and over, but overall I think it's a great idea. Either way it's a vast improvement over what's in video games now. I do think they could have greatly improved the look of their results by making the fabric less shiny though - it made everything seem like silk or satin, even if it was supposed to be a heavy linen.

4/5 Simulating Leaping/Physics of Dance

For the first paper, I was surprised that the knees are barely considered for keeping balance. It makes sense for examples where, say, you're standing still and someone pushes you from behind. In that case, you react mostly by bending forward at the hip, and I'm sure you subconsciously do something with your ankles too. However, the knees are barely used. But what about in the example where the gymnast is trying to stick her landing? She bends her knees a lot there. I suppose you could say that the knees are for the impact and the hips and ankles are for balance, but since it's all one motion I feel like the knees would have to be considered. Maybe it's that I don't entirely understand the physics of it, but I feel like if you're falling or jumping, you use your knees a lot to maintain balance.

As a dancer, I found Physics of Dance to be pretty interesting, too. A lot of the different physical corrections suggested for balance were a bit funny to me, because I don't think about those things at all when I dance. The best solution for balance, I find, is to clench my abs. Of course, I don't really know how that effects things like center of mass, angular momentum, etc.

3/29 Optimizing Walking Controllers

This paper was pretty much an improvement on Simbicon. In order to fix the problem of characters stomping, they added joints in the feet to allow them to curve, as we do due to our toes. It was an improvement, but it still looked bizarre. We mentioned in class though that everyone that tries to add toes keeps their characters seemingly barefoot - I wonder if it wouldn't look so strange if they had the toes move inside shoes. Or even restrict the feet to bend based on the flexibility of most shoes. Either way, the toes were bending too much for too long, creating a really strange motion. Another thing that struck me was how different the results looked when adapted for different body types. The regular, short, and overweight bodies looked awkward, but the tall and thin bodies looked a lot better - believable almost! We haven't see any research that examines how motions differ between people of different body types, but I think that could be useful. It might be that this paper's method is ideal for tall and lean bodies, whereas other equations might be better for short and squat. I think a lot of researchers tend to neglect the many differences in the human body, and treat motions as if they are the same for everyone. Of course, we should perfect one walk before we try to perfect them all, but I do think this is something people should look into.