Methods of Reducing the Visibility of Mach Bands during Gouraud Shading


Mach bands are illusory artefacts caused by the human visual system providing edge amplification in regions containing a discontinuity in the gradient of light intensity. Gouraud shading attempts to produce smooth surfaces using a polyhedral mesh as a base geometry, and is commonly considered to have visible edge effects due to Mach bands along polygon boundaries.

We investigate factors which affect the visibility of Mach bands. Experimental results indicate the intensity of Mach bands drops off with higher orders of continuity in the interpolation function. Width of the interpolation region also plays a role, although it is possible to reduce the visibility of Mach bands for very narrow interpolation regions.

An adapted Gouraud shader is created which corrects for these factors. Remaining edge effects are attributed to a number of other perceptual issues which have not been previously associated with Gouraud shading. Corrections for these effects are also described, resulting in further shader variations which can use efficient Gouraud shading strategies for the bulk of the polygon, and alternative interpolation strategies where Mach bands occur.


Technical Reports

[1] Shaun Bangay. Methods of reducing the visibility of Mach bands during Gouraud shading. Technical report, Virtual Reality Special Interest Group, Computer Science Department, Rhodes University, Grahamstown, South Africa, November 2002. [PDF] [BibTeX]