icetStrategy -- set the strategy used to composite
images.
#include <IceT.h>
| void icetStrategy( |
IceTEnum |
strategy ); |
The IceT API comes packaged with several algorithms for
compositing images. The algorithm to use is determined by selecting a
strategy. The strategy is selected with icetStrategy. A
strategy must be selected before icetDrawFrame,
icetCompositeImage, or icetGLDrawFrame is called.
A strategy is chosen from one of the following provided enumerated
values:
- ICET_STRATEGY_SEQUENTIAL
-
Basically applies a ``traditional'' single tile composition (such as binary
swap) to each tile in the order they were defined. Because each process
must take part in the composition of each tile regardless of whether they
draw into it, this strategy is usually inefficient when compositing for
more than one tile, but is recommended for the single tile case because it
bypasses some of the communication necessary for the other multi-tile
strategies.
- ICET_STRATEGY_DIRECT
-
As each process renders an image for a tile, that image is sent directly to
the process that will display that tile. This usually results in a few
processes receiving and processing the majority of the data, and is
therefore usually an inefficient strategy.
- ICET_STRATEGY_SPLIT
-
Like ICET_STRATEGY_DIRECT, except that the tiles are split up, and
each process is assigned a piece of a tile in such a way that each process
receives and handles about the same amount of data. This strategy is often
very efficient, but due to the large amount of messages passed, it has not
proven to be very scalable or robust.
- ICET_STRATEGY_REDUCE
-
A two phase algorithm. In the first phase, tile images are redistributed
such that each process has one image for one tile. In the second phase, a
``traditional'' single tile composition is performed for each tile. Since
each process contains an image for only one tile, all these compositions
may happen simultaneously. This is a well rounded strategy that seems to
perform well in a wide variety of multi-tile applications. (However, in
the special case where only one tile is defined, the sequential strategy
is probably better.)
- ICET_STRATEGY_VTREE
-
An extension to the binary tree algorithm for image composition. Sets up a
``virtual'' composition tree for each tile image. Processes that belong to
multiple trees (because they render to more than one tile) are allowed to
float between trees. This strategy is not quite as well load balanced as
ICET_STRATEGY_REDUCE or ICET_STRATEGY_SPLIT, but has very
well behaved network communication.
Not all of the strategies support ordered image composition.
ICET_STRATEGY_SEQUENTIAL, ICET_STRATEGY_DIRECT, and
ICET_STRATEGY_REDUCE do support ordered image composition.
ICET_STRATEGY_SPLIT and ICET_STRATEGY_VTREE do not support
ordered image composition and will ignore ICET_ORDERED_COMPOSITE if
it is enabled.
Some of the strategies, namely ICET_STRATEGY_SEQUENTIAL and
ICET_STRATEGY_REDUCE, use a sub-strategy that composites the image
for a single tile. This single image strategy can also be specified with
icetSingleImageStrategy.
Copyright (C)2003 Sandia Corporation
Under the terms of Contract DE-AC04-94AL85000 with Sandia
Corporation, the U.S. Government retains certain rights in this
software.
This source code is released under the New BSD License.