Browse Prior Art Database

Fast Hardware Area Fill using Block Write Cycles

IP.com Disclosure Number: IPCOM000104409D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Lawless, W: AUTHOR

Abstract

This article will discuss an area fill procedure that reduces the number of video memory write cycles it takes to fill a polygon by using block wite cycles mode. By reducing the number of cycles this will increase performance by 37.5% over fills done using normal write cycle mode.

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Fast Hardware Area Fill using Block Write Cycles

      This article will discuss an area fill procedure that reduces
the number of video memory write cycles it takes to fill a polygon by
using block wite cycles mode.  By reducing the number of cycles this
will increase performance by 37.5% over fills done using normal write
cycle mode.

      Block write cycles allow 4 adjacent pixels in one video module
to be written with the same color in one cycle.  When 5 video memory
modules are used then 20 pixels can be written in one cycle.

      For ease of drawing the polygon to be filled is the smaller
rectangle and the fill extents are done within the larger rectangle
(Figure).

      The polygon is drawn in a working plane and an edge sorting
algorithm is used to determine which pixels are filled and which are
not.  Pixels are read from the working plane and when a line (polygon
edge) is crossed filling begins and when another line (polygon edge)
is crossed filling stops; this is straightforward and done in the
prior art.  Due to the bandwidth of the bus only 5 edge pixels can be
loaded and 5 filled pixels stored into the frame buffer in a single
cycle.  With this invention, 5 pixels are loaded at a time to fill a
20-pixel mask,  again turning on filling then off for each crossing
of the edge, similar to before.  Pixels must also be aligned with
20-pixel boundaries of the VRAMs by shifting them at the beginning of
the fill rectangle for each scan line.

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