Tag Archive: siggraph


SIGGRAPH paper summary: Art-Based Rendering Of Fur, Grass, Trees by Michael Kowalski, et al.

A (sort of) particle-based system for an illustrative style of rendering to balance screen-space density of strokes against world-spatial coherence to provide some interframe coherence. Starts with a conventionally-rendered image as reference and places graphtals* according to a “desire” map. As each stroke is placed, it subtracts a blurred version of itself from the desire map, and so on until the desire map is filled, thus preventing overly dense stroke placement. Provides techniques for scaling strokes in screen space as they scale in camera space (does that make any sense?), for deciding how much of the stroke to draw based on factors such as surface facing angle, and for reducing strokes as they are no longer needed to reduce popping. The individual stroke aligns itself to the camera based on user rules such as “always point down” for fur or “always orient clockwise” for truffula tufts. The technique does not fully solve problems of interframe coherence, but gives a starting point.

*Alvy Ray Smith’s concept of “graphtals” (a portmanteau of fractals and graphics): image information that is generated algorithmically/implicitly and only when requested.

Overall this is a idea with potential. The paper points to a lot of interesting prior work, too. Another Brown University project!

Computer-Generated Watercolor by Cassidy J. Curtis, Sean E. Anderson, Joshua E. Seims, Kurt W. Fleischer, David H. Salesin

Presents a series of techniques for modeling the behavior of watercolor paint on paper in rather thorough detail. Simulates edge-darkening, backruns, glazing, dry-brush, and several other characteristics of watercolor. The technique can be used for painting ala Photoshop, although the paper notes that interactive painting is impossible with the current technology (133 MHz SGI R4600 chip!), creating watercolor from a photograph with manually specified mattes, or from a 3D render. Temporal coherence is not solved (the technique is prone to ’shower-door’ artifacts), but the single-frame results are quite nice. It’s a considerably more advanced model than the one used by Painter or Photoshop.


Siggraph Paper Summary: Rendering Parametric Surfaces in Pen and Ink by Georges Winkenbach & David H. Salesin, University of Washington

I can still remember the first SIGGRAPH I attended in 1996. By the generosity of MTV Networks, I had a full conference pass which meant conferences and papers (which I barely attended) and the full set of publications, which I devoured eagerly afterwards. This paper really blew my mind, and I still think it’s a technique with a lot of potential that hasn’t been well exploited. Way cooler than

Winkenbach’s paper presents what looks like a robust technique for inking parametric (i.e. NURBS) surfaces. Ink line direction is controlled by surface parameter, the tone by modulating stroke thickness. Strokes can be sharp or wiggly, short strokes become stippling. Tone can be controlled by lighting (they present a technique for shadows), by texture map, or something else (i.e. reflection mapping).

The technique could probably be adapted to utilize UV mapping coordinates. The authors tantalizingly suggest generating strokes “along directions that aremore intrinsic to the geometry of the surface—for example, along directions of principal curvature.” Not addressed as far as I can tell is temporal coherence. What does this technique look like over a series of frames, when the surface is translating and deforming?

This approach is not available in any commercial package that I am aware of, but I wish it were.

Powered by WordPress. Theme: Motion by 85ideas.