Scan-Line Conversion &
Z-buffer Hidden Surface Removal
Andrew G. Zaferakis
UNC Chapel Hill
COMP 236 Spring 2000
Homework 3 - Triangle Rasterization
    The model below is composed of 3,000 triangles, thanks to Kenny Hoff for the model.  On the left is the model viewed using SoftGL, which contains our own homogeneous clipper, matrix stack, and triangle rasterizer.  On the right is the OpenGL rasterization, as you can tell, the two images are identicle, each pixel matches.  When viewing this you can swap between SoftGL and OpenGL by pressing the spacebar, there will be no changes in the pixels.  The only allowable changes are when there are two co-planar polygons which causes z-fighting, a known problem that exists even in hardware.  The SoftGL is comparable in speed to the OpenGL for small models, however as the polygon count increases, the hardware will always win.  This model has very little slowdown when viewing, try it out!
 
SoftGL
OpenGL

 
SoftGL Viewer Controls
Mouse  Used to Rotate
Left Button Locks mouse movements to controls
ESC Exit
SPACE Toggle SoftGL vs OpenGL mode

    The following pictures have been generated in LightScape and exported as triangles, thanks to Paul McLaurin.  This model is composed of 47,781 triangles.  As you can tell the model has been radiositized and this the color shown here is per-vertex, the SoftGL code is doing no color interpolation, just flat shading.  The density of the triangles is what gives us a smooth looking model.  The first picture is the outside of a building, the second is a view from the inside.  Click on the image for a larger view.  As before there are no differences between the SoftGL rasterization and the OpenGL rasterization.  Check back in future assignments to see SoftGL in a bigger, bolder, more robust form performing phong shading, texturing, lighting and plenty more.
 

SoftGL
OpenGL
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