Samuel Wang

I. Design
        The texturing was easily added to the primitive.material() interface designed for
project 2.  This function returns all of the material properties of a primitive
at a particular point.  For example, in triangles a barycentric calculation was used to determine
the s, t, texture coordinates at a given point in the triangle.  The interpolated
s, and t values were then used to select the appropriate texels from the texture map.
        A bilinear filter was used to blend texels to produce a pixel color.  The
s, and t ({0 to 1, 0 to 1} space )coordinates were transformed to u, and v
({0 to texture.width, 0 to texture.height} space ) coordinates.  In general, the texture
coordinates had some fractional distance between texels in both u and v directions.
Thus, 4 nearest texels were selected and blended linearly in 2 dimensions using the fractional
bits as the blending factor.
        Specular color modulation was implemented by using a second texture map.  The first
texture map was used to determine the r, g, b diffuse colors.  The red channel
of the second texture map was used to select the specular color of the primitive from 2
possible object materials  (These materials are loaded in the usual manner).  

II Images
        One rendered image demonstrating all required elements is provided.  The author
did not have consistant access to the SGI platform, and all associated modeling tools.  The 
entire scene geometry was hand designed and hard coded into the program.  Not that all objects
appear to be at right angles to each other in the scene.  This was done to preserve the
author's sanity.  Note that a trivial modification would allow an appropriately designed scene
to be loaded in from file.
        The image was sampled at 800 x 800 resolution.  The hard coded geometry rendered
quickly, so an adaptive supersampling scheme was not implemented.  The soft appearance of the
image is due to the bilinear texture filtering.



A.  Pop Tart Box
        The pop tart box was the first textured object that was constructed.  This object
consists of 12 triangles and 6 associated texture maps for the rectangle faces.  The
texture maps were scanned from some refuse left in the author's apartment.  This object
demonstrates the basic texturing functionality.

B.  Sphere
        The sphere demonstrates the required texture mapping onto a sphere element.  The custom 
Earth texture was obtained from http://www.fourmilab.ch/cgi-bin/uncgi/Earth.  The basic formula 
from page 48 of Glassner's "An Introduction to Ray Tracing" was used.

C.  Floor
        The floor consists of 2 large triangles mapped with a procedurally generated texture.
The floor demonstrates the texture wrapping functionality.  Note that the generated texture
was a 2 x 2 checker.
        The floor also demonstrates the effects of the bilinear filter.  Zooming in on the 
checker borders shows the blending between blue and white.
        The checker pattern was originally selected to produce some Moire pattern artifacts.  
However, the author did not have time to finish his MIP mapping / Trilinear filtering extension.

        
D.  Game CD
        The CD was modeled with 12 triangles, diffuse color textures, and 1 specular color texture.  The
CD demonstrates the modulation of specular color using textures.  Note that the "Sam  Wang" name
label does not reflect the color of the Pop Tart Box.  Also note that the black binding on the
left hand side of the CD jewel case also does not reflect the Pop Tart's specular color.  These elements
were NOT modeled using geometry.  The CD case does consist of only 12 triangles, (2 for each box face).
        The red channel of the specular color map was used to select between the specular of colors
of different object materials ( 2 materials in this case ).  The green and blue channels are left
free for future extensions.
        The specular color texture map for the label and CD binding was constructed by hand
from the diffuse texture using Paint Shop Pro.