Computers and knitting needles: what do these have in common? According to computer graphics researchers, both can now be used to knit – creating virtual garments in the computer’s case. The team, who worked together at Cornell University in the USA, developed a method for generating computer-simulated knitted materials for animation. They presented their work in early August at the 39th International Conference and Exhibition of Computer Graphics and Interactive Techniques (SIGGRAPH) in Los Angeles.
When you’re watching the latest Pixar movie, the clothing shouldn’t distract you from the action, but it’s tricky to animate clothes that appear to hang and move realistically. Characters rarely sport woolly jumpers because simulating yarn stitches is even more complicated than creating a smoother fabric.
On a computer, a mesh grid or sheet provides the basis for modeling regular fabric. It deforms to accommodate the wearer’s body and show motion, following rules from geometry and physics. Simulating knits took extra steps. The Cornell team developed 3-D models of various individual stitches. Like in knitting, these single stitches are repeated to make up a complete garment.
To be realistic, each stitch can also stretch. As team member Dr. Steve Marschner explained in a press release, "We are actually changing the shape of the yarn loops that make up the stitches, simulating how they wrap around other loops." The method also includes options for adjusting the thickness of the yarn and the tension in the knitting. The team has successfully tested their technique on several patterns, including a tea cozy and a jumper for a sheep.
All of the detail, however, makes the computer simulations computationally intensive. The researchers reported that simulating one of their knitted creations takes several hours, but chilly, fashion-conscious animated characters may feel it’s worth the wait.
Original publication: http://www.cs.cornell.edu/projects/stitchmeshes/
Photo credit: Cornell University
Posted on Monday, 27th August, 2012