What's the best way to get 3D characters in videogames to look real and expressive? Two computer scientists at Université de Montréal have come up with answer: use simple bitmap sketches to make their poses more lifelike.
Assistant professor Mikhail Bessmeltsev and his PhD student Kirill Brodt have developed an animation tool that uses drawings to control how videogame characters stand and move in three dimensions.
The duo's study is published on July 22 in ACM Transactions on Graphics. We asked them to tell us more.
Video games: posing in 3D
What was the challenge you faced in coming up with this new tool?
Artists frequently capture character poses via raster sketches; the process is called storyboarding. They then use these drawings as a reference while posing a 3D character in their software. This is a time-consuming process that requires specialized 3D training and mental effort. What we've done is create the first software to automatically infer a 3D character pose from a single bitmap sketch, producing poses that are consistent with what the viewer expects to see.
What do you do to overcome these problems?
We address them by predicting three key elements of a drawing that are needed to disambiguate the drawn poses: 2D bone tangents (how is each body part rotated in the sketch?), self-contacts (is the left hand touching the head?), and bone foreshortening. We then look for a 3D pose that has all those elements exactly preserved via an optimization. We validate our method by showing that the final 3D character's pose is the pose an observer sees in a sketch.
