Researchers put the shine on digitally rendered feathers

ITHACA, N.Y. – Computer animators and video game designers may soon have a better way to create the purple-green sheen of a grackle’s wing, or the pink flash on a hummingbird’s throat, thanks to a new method for rendering iridescent feathers developed by Cornell University and NVIDIA Corporation researchers.

Researchers in the lab of Steve Marschner, professor of computer science, and NVIDIA Research, modeled how light reflects off different types of iridescent bird feathers. Using specimens from the Cornell Lab of Ornithology as a reference, they rendered digital images that change colors at different angles and, unlike earlier models, incorporate tiny variations that give real feathers their glittery appearance.

“Natural iridescent things will always have these imperfect qualities,” Marschner said.

Researchers chose birds for their first attempt at modeling biological iridescence because feathers are easy to work with.

“Bird feathers have the advantage that the structures are kind of sitting there, right on the surface, so they’re not buried under, say, fish skin … or a lot of other structures to simulate,” Marschner said.

The work, published in ACM Transactions on Graphics, included seven species, which covered the different types of iridescence in birds and whose nanostructures had been determined previously – mallard, rock dove, bronzewing, peacock, magpie, starling and hummingbird.

The process quickly and accurately yields individual feathers and parts of birds that shine and change colors in the light. The next step will be to incorporate the model into a more artist-friendly interface, researchers said, so designers can apply it in video games and animation.

“Even though it takes a lot of computation to build these models, using them in the end is pretty efficient,” Marschner said. “You could definitely imagine getting these into a real-time implementation where you could use them in a virtual environment, or a video game.”

Ultimately, this work could also be expanded to render entire birds and other iridescent animals, though additional modeling will be needed to render the effects of the pigments in the skin of animals like octopus and fish.

The work received support from the National Science Foundation and NVIDIA Corporation.

For additional information, see this Cornell Chronicle story.

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