Browse Prior Art Database

Window Draw Extents for Animation and Control Plane Clearing

IP.com Disclosure Number: IPCOM000122263D
Original Publication Date: 1991-Nov-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 4 page(s) / 133K

Publishing Venue

IBM

Related People

Jensen, AP: AUTHOR [+2]

Abstract

Prior art for clearing of windows between frames clears the entire extent of the window (or even the entire screen with window mask). This invention presents a method for clearing only the extents of the object drawn in a window using either conventional blit or block fill mode.

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

Window Draw Extents for Animation and Control Plane Clearing

      Prior art for clearing of windows between frames clears
the entire extent of the window (or even the entire screen with
window mask).  This invention presents a method for clearing only the
extents of the object drawn in a window using either conventional
blit or block fill mode.

      The following proposal elaborates the details of a graphics
rendering hardware enhancement which would help decrease window clear
time.  The basic idea is for the rendering hardware to maintain
registers with the maximum and minimum draw coordinates for
operations into the frame buffers, z-buffer, and control planes.
There would be one global extents register.

      Fig. 1 illustrates how the basic idea would work.  In most
windows (animated or still-frame 2D or 3D) there is a central focus
to the image displayed and, typically, the image is scaled to fit
into the window with some unused border.  If the extents of the
objects drawn into the window are known, then clearing the window to
the same background style and color can be accelerated by clearing
only the portion of the window updated since the last clear.  If the
clear is of the same pattern as the current background, the blit will
be accelerated by reducing the area of the pattern/hatched fill to
only the area used since the last clear.  If the background is a
solid color, the clear can be further accelerated by using the block
fill mode available in some video dynamic rams.

      Fig. 2 depicts the registers in graphics rendering hardware
which would need to be added:
1) The x_min and x_max will be expressed in terms of block clear
boundaries.  Thus, x_max and x_min will each specify one of the 64
block-clear blocks.  A value of x_max or x_min = 0 specifies the
leftmost column of blocks.
2) The y_min and y_max will be expressed in terms of blocks of 32
scan lines (arbitrary choice to limit compare hw size).  A value of
y_max or y_min = 0 specifies the topmost column of blocks.
3) The block fill/clear function will use the values in registers
'07'X and '09'X for the extents of the fill/clear.  These are the
same registers used to specify the extents for n...