Browse Prior Art Database

Fast Span Processing for 3D Graphics Rasterization with Double Pixel Operations Technique

IP.com Disclosure Number: IPCOM000118277D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Kwok, TY: AUTHOR [+2]

Abstract

Disclosed is a method to improve the efficiency of any software rasterizer for 3D graphics by performing the span processing on two pixels instead of one pixel at a time during each triangle or polygon rasterization.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Fast Span Processing for 3D Graphics Rasterization with Double Pixel
Operations Technique

      Disclosed is a method to improve the efficiency of any software
rasterizer for 3D graphics by performing the span processing on two
pixels instead of one pixel at a time during each triangle or polygon
rasterization.

      The Figure shows the most common rasterization
algorithm.  There are three steps in this rasterization algorithm.
First, the step is called the triangle or polygon processing.  In
this step, the initial scan line intersected by the triangle or
polygon is determined either by the vertex with the smallest  or
largest y value.  The second step is called edge processing.  The x,
z, R, G, and B values at the intersection points of the left and
right edges with the current scan line are calculated in this step.
The third  step is called the span processing.  During this step, z,
R, G, and B values are calculated for each pixel within the span.
The z value is compared with the previous z value stored at that
location.  If it is smaller, the new pixel value replaces the old
one.  The calculation starts from either the left P sub l or the
right P sub r edge intersection point and stops at the other edge
intersection point. Thus,  there are two condition statements for
each pixel within the span to test  whether the pixel is within the
span and its z value is smaller than the  previous value.

      The method in this disclosure is to speed up the span
processing by testing every other pixel instead of every pixel for
within the span or not.  As shown in the Figure, the first point...