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Technique for Rendering Opaque Stippled Objects Using Block Write

IP.com Disclosure Number: IPCOM000117980D
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Brady, M: AUTHOR [+5]

Abstract

This paper describes a method of rendering opaque stippled objects which utilizes the block write feature of Video RAMs (VRAMS). Exploitation of the block write feature increases the performance of rendering opaque stippled objects. Block Write mode allows n successive pixels to be written in the time normally taken to write one pixel by utilizing a mask and the value in the color register.

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Technique for Rendering Opaque Stippled Objects Using Block Write

      This paper describes a method of rendering opaque stippled
objects which utilizes the block write feature of Video RAMs
(VRAMS).  Exploitation of the block write feature increases the
performance of rendering opaque stippled objects.  Block Write mode
allows n successive pixels to be written in the time normally taken
to write one pixel by utilizing a mask and the value in the color
register.

      A stipple pattern consists of a binary string.  For transparent
mode, wherever a one occurs in the pattern the foreground color is
written, otherwise nothing is written thus retaining the original
pixel value in the frame buffer.  In opaque mode, wherever a one
occurs in the  pattern the foreground color is written, otherwise the
background color  is written.  This is illustrated in Fig. 1.

      Transparent stipple lends itself very well to the Block Write
operation.  Simply load the VRAM color register with the foreground
color and use the stipple pattern (assume that the stipple pattern
has already  been loaded into the stipple cache) as the mask during
the block write  operation.  This produces exactly the pattern for
the transparent example  above with n pixels being written every
write cycle.  Opaque stipple requires two different values be written
to the frame buffer.  This requires a separate write cycle for each
pixel.  Therefore, transparent  stipple is n times faster t...