Nav: Home

How a computer learns to dribble: Practice, practice, practice

August 07, 2018

Basketball players need lots of practice before they master the dribble, and it turns out that's true for computer-animated players as well. By using deep reinforcement learning, players in video basketball games can glean insights from motion capture data to sharpen their dribbling skills.

Researchers at Carnegie Mellon University and DeepMotion Inc., a California company that develops smart avatars, have for the first time developed a physics-based, real-time method for controlling animated characters that can learn dribbling skills from experience. In this case, the system learns from motion capture of the movements performed by people dribbling basketballs.

This trial-and-error learning process is time consuming, requiring millions of trials, but the results are arm movements that are closely coordinated with physically plausible ball movement. Players learn to dribble between their legs, dribble behind their backs and do crossover moves, as well as how to transition from one skill to another.

"Once the skills are learned, new motions can be simulated much faster than real-time," said Jessica Hodgins, Carnegie Mellon professor of computer science and robotics.

Hodgins and Libin Liu, chief scientist at DeepMotion, will present the method at SIGGRAPH 2018, the Conference on Computer Graphics and Interactive Techniques, Aug. 12-18, in Vancouver.

"This research opens the door to simulating sports with skilled virtual avatars," said Liu, the report's first author. "The technology can be applied beyond sport simulation to create more interactive characters for gaming, animation, motion analysis, and in the future, robotics."

Motion capture data already add realism to state-of-the-art video games. But these games also include disconcerting artifacts, Liu noted, such as balls that follow impossible trajectories or that seem to stick to a player's hand.

A physics-based method has the potential to create more realistic games, but getting the subtle details right is difficult. That's especially so for dribbling a basketball because player contact with the ball is brief and finger position is critical. Some details, such as the way a ball may continue spinning briefly when it makes light contact with the player's hands, are tough to reproduce. And once the ball is released, the player has to anticipate when and where the ball will return.

Liu and Hodgins opted to use deep reinforcement learning to enable the model to pick up these important details. Artificial intelligence programs have used this form of deep learning to figure out a variety of video games and the AlphaGo program famously employed it to master the board game Go.

The motion capture data used as input was of people doing things such as rotating the ball around the waist, dribbling while running and dribbling in place both with the right hand and while switching hands. This capture data did not include the ball movement, which Liu explained is difficult to record accurately. Instead, they used trajectory optimization to calculate the ball's most likely paths for a given hand motion.

The program learned the skills in two stages -- first it mastered locomotion and then learned how to control the arms and hands and, through them, the motion of the ball. This decoupled approach is sufficient for actions such as dribbling or perhaps juggling, where the interaction between the character and the object doesn't have an effect on the character's balance. Further work is required to address sports, such as soccer, where balance is tightly coupled with game maneuvers, Liu said.
-end-


Carnegie Mellon University

Related Video Games Articles:

Video games can change your brain
Scientists have collected and summarized studies looking at how video games can shape our brains and behavior.
Researchers find video games influence sexist attitudes
The images and roles of female characters in video games send a powerful message that can influence the underlying attitudes of gamers.
Playing to beat the blues: Video games viable treatment for depression
Video games and 'brain training' applications are increasingly touted as an effective treatment for depression.
Violent video games found not to affect empathy
The link between playing violent video games and antisocial behavior, such as increased aggression and decreased empathy, is hotly debated.
Brain training video games help low-vision kids see better
A new study by vision scientists at the University of Rochester and Vanderbilt University found that children with poor vision see vast improvement in their peripheral vision after only eight hours of training on kid-friendly video games.
Teenagers influenced by video games with alcohol and smoking content
A new study has found that modern popular video games commonly feature alcohol and smoking content and the teenagers who play them are twice as likely to have tried drinking and smoking themselves.
How long should children play video games?
A new study indicates that playing video games for a limited amount of time each week may provide benefits to children, but too much can be detrimental.
Are violent video games associated with more civic behaviors among youth?
Whether violent video games influence the behavior of youth has been a debate that has split the academic community for years.
Serious video games may help increase fruit and vegetable intake
Using a serious video game, Squires Quest! II: Saving the Kingdom of Fivealot, researchers from the United States Department of Agriculture / Agricultural Research Service Children's Nutrition Research Center at Baylor College of Medicine and Texas Children's Hospital evaluated how creating implementation intentions (i.e., specific plans) within the goal-setting component in the game helped fourth and fifth grade students improve fruit and vegetable intake at specific meals.
Sexist video games decrease empathy for female violence victims
Young male gamers who strongly identify with male characters in sexist, violent video games show less empathy than others toward female violence victims, a new study found.

Related Video Games Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Changing The World
What does it take to change the world for the better? This hour, TED speakers explore ideas on activism—what motivates it, why it matters, and how each of us can make a difference. Guests include civil rights activist Ruby Sales, labor leader and civil rights activist Dolores Huerta, author Jeremy Heimans, "craftivist" Sarah Corbett, and designer and futurist Angela Oguntala.
Now Playing: Science for the People

#520 A Closer Look at Objectivism
This week we broach the topic of Objectivism. We'll be speaking with Keith Lockitch, senior fellow at the Ayn Rand Institute, about the philosophy of Objectivism as it's taught through Ayn Rand's writings. Then we'll speak with Denise Cummins, cognitive scientist, author and fellow at the Association for Psychological Science, about the impact of Objectivist ideology on society. Related links: This is what happens when you take Ayn Rand seriously Another Critic Who Doesn’t Care What Rand Thought or Why She Thought It, Only That She’s Wrong Quote is from "A Companion to Ayn Rand"