Collision-free construction of animated feathers using implicit constraint surfaces

Abstract

We present a scheme for constructing complex feather geometry suitable for feature animation. The key points of our approach include the use of a potential field derived from guide geometry and an implicit constraint surface to create nonpenetrating feather geometry. Our method is frame independent and produces visually smooth animation that is free from popping and other visual artifacts. We provide details of the implementation and examples of the technique applied to an animated character with several thousand feathers.

An Efficient Feathering System with Collision Control

“…These feathers are difficult to be adjusted automatically and would require manual adjustments. Similar cases also exist in [CXGS02,WG09].…”

“…Feathering the bird, however, is far more complicated because the feathers have to be neatly stacked over the skin surface without penetrating each other. It is considered difficult and time-consuming to achieve a desired coverage of feathers manually, or even with automatic algorithms such as [WG09]. Another challenge is how to incrementally adjust the feathers when the bird is animated, because re-generating all the feathers per frame takes too much overhead.…”

“…Birds are one of the most common wildlife in our daily life. Computer graphics researchers have produced a number of models to model the bird and its animation [KC02, CXGS02, WP03, WG09, JWL*13]. Feather construction is at the heart of bird modeling in that the feather is one of the key features to distinguish different species of birds and is important in flight simulation.…”

“…We start by designing the feather distribution over the body. Traditionally, the feather guides are created and placed on the skin surface, which are then interpolated to get the feathers on the rest feather roots [CXGS02, KC02, WG09]. Typically, thousands of feathers require tens or hundreds of guides [WG09].…”

“…Traditionally, the feather guides are created and placed on the skin surface, which are then interpolated to get the feathers on the rest feather roots [CXGS02, KC02, WG09]. Typically, thousands of feathers require tens or hundreds of guides [WG09]. This number of guides, however, may still be difficult and cumbersome to initialize, because the properties of the guides, including the positions, orientations, shapes and sizes, need to be smoothly transited over the surface in order to obtain a good interpolation result.…”