Discontinuity edge overdraw
Symposium on Interactive 3D Graphics (I3D) 2001, 167-174.
Antialiased edges rendered along silhouettes to remove spatiotemporal jaggies.
Aliasing is an important problem when rendering triangle meshes. Efficient antialiasing techniques such as
mipmapping greatly improve the filtering of textures defined over a mesh. A major component of the
remaining aliasing occurs along discontinuity edges such as silhouettes, creases, and material boundaries.
Framebuffer supersampling is a simple remedy, but 2x2 supersampling leaves behind significant temporal
artifacts, while greater supersampling demands even more fill-rate and memory. We present an alternative
that focuses effort on discontinuity edges by overdrawing such edges as antialiased lines. Although the
idea is simple, several subtleties arise. Visible silhouette edges must be detected efficiently.
Discontinuity edges need consistent orientations. They must be blended as they approach the silhouette to
avoid popping. Unfortunately, edge blending results in blurriness. Our technique balances these two
competing objectives of temporal smoothness and spatial sharpness. Finally, the best results are obtained
when discontinuity edges are sorted by depth. Our approach proves surprisingly effective at reducing
temporal artifacts commonly referred to as "crawling jaggies", with little added cost.
Since hardware framebuffer multisampling is becoming standard and
inexpensive, our proposed solution may have come too late.