Homan Igehy

CS348b Project - Lacquered Guitar

The Crawl

Crawl: MPEG movie (69 KB) of a reflection crawling across the wood grain.

Video Capture of Actual Guitar

Image One

Full Size - 1280 x 1024 JPEG (141 KB)

Image Two

Full Size - 1280 x 1024 JPEG (137 KB)

Image Three

Full Size - 1600 x 2000 JPEG (417 KB)

Statement of Purpose

These images were created for the CS 348B class at Stanford University in the Computer Science Department. The course project was to write a raytracing-based rendering engine and create pretty pictures for the class competition; this entry won.

  • CS 348B 1995 Rendering Competition
  • CS 348B Rendering Competition
  • Cool Demos

    Boring Explanations

    The goal of my project was to model my classical guitar using a ray tracer.

    The physical shape of the guitar was created using i3dm, a demo modeler found on all SGI's. (Some hand tweaking had to be done in order to get proper texture coordinates on the top and bottom faces of the guitar.)

    The main focus of my work was to correctly simulate the reflections off of unsanded, lacquered wood. The face of the guitar demonstrates this best. A scanned image of the actual wood serves as a basis for a texture map. The color variations in this map are used as a height field from which a bump map is derived. This bump map is adjusted so that color variations across the grain cause more of a height difference than color variations along the grain. This gives a better correspondence between color and bump. The texture map is tiled several times, and through some hacking, the mosaic was placed on top of the guitar as "mosaic map". Furthermore, a "wavy" function is added to the bump map to simulate the warping of the wood.

    The bridge, neck, sides, and bottom of the guitar were created in a similar manner.

    The fretboard was modeled by a combination of a texture map, reflection map, and bump map derived from scannings of the actual fretboard.

    The strings are modeled by small parallelepipeds with interpolated normals. The are partially reflective and partially refractive, mocking the material properties of nylon strings.

    The mirror on the left has that annoying blurring effect found on all mirrors (though I exaggerate the effect). Because mirrors are just a layer of silver on the back of a piece of glass, there is a small amount of reflection of the top layer of the glass. I model this as a surface phenomenon.

    Thanks to Graciela Casas-Silvas for her late-night Taco Bell and image scanning.

    Homan Igehy