A Tiny Example Based Procedural Model for Real-Time Glinty Appearance Rendering

The glinty details from complex microstructures significantly enhance rendering realism.However,the previous methods use high-resolution normal maps to define each micro-geometry,which requires huge memory overhead.This paper observes that many self-similarity materials have independent structural characteristics,which we define as tiny example microstructures.We propose a procedural model to represent microstructures implicitly by performing spatial transformations and spatial distribution on tiny examples.Furthermore,we precompute normal distribution functions(NDFs)by 4D Gaussians for tiny examples and store them in multi-scale NDF maps.Combined with a tiny example based NDF evaluation method,complex glinty surfaces can be rendered simply by texture sampling.The experimental results show that our tiny example based the microstructure rendering method is GPU-friendly,successfully reproducing high-frequency reflection features of different microstructures in real time with low memory and computational overhead.

Virtual hairy brush for digital painting and calligraphy

The design of user friendly and expressive virtual brush systems for interactive digital painting and calligraphy has attracted a lot of attention and effort in both computer graphics and human-computer interaction circles for a long time. Providing a digital environment for paper-less artwork creation is not only challenging in terms of algorithmic design, but also promising for its potential market values. This paper proposes a novel algorithmic framework for interactive digital painting and calligraphy based a novel virtual hairy brush model. The algorithms in the kernel of our simulation framework are built upon solid modeling techniques. Implementing the algorithms, we have developed a virtual hairy brush prototype system with which end users can interactively produce high-quality digital paintings and calligraphic artwork. (The latest progress of our virtual brush project is reported at the website “http://www.cs.hku.hk/~songhua/e-brush/”.)

Time-varying clustering for local lighting and material design

This paper presents an interactive graphics processing unit （GPU）-based relighting system in which local lighting condition, surface materials and viewing direction can all be changed on the fly. To support these changes, we simulate the lighting transportation process at run time, which is normally impractical for interactive use due to its huge computational burden. We greatly alleviate this burden by a hierarchical structure named a transportation tree that clusters similar emitting samples together within a perceptually acceptable error bound. Furthermore, by exploiting the coherence in time as well as in space, we incrementally adjust the clusters rather than computing them from scratch in each frame. With a pre-computed visibility map, we are able to efficiently estimate the indirect illumination in parallel on graphics hardware, by simply summing up the radiance shoots from cluster representatives, plus a small number of operations of merging and splitting on clusters. With relighting based on the time-varying clusters, interactive update of global illumination effects with multi-bounced indirect lighting is demonstrated in applications to material animation and scene decoration.