HP SVA V2.0 Parallel Compositing Reference Guide

There are benefits to using multiple graphics cards rather than a single card. The benefits arise
from scaling in the resources of the graphics card and the host system, as follows:
Scaled Host System ResourcesScaled Graphics Card Resources
Amount of host memoryAvailable texture memory
Bandwidth between host memory and the graphics cardOverall size of the image produced
Amount of geometry that can be processed
The Library exploits a scaling technique called Sort-last rendering. Using the sort-last rendering
technique, a number of graphics cards produce “sub-images” that make up some part of the final
image. Compositing operators then combine these sub-images to produce the final image. Sort-last
rendering differs from another common technique called Sort-first rendering. In sort-first rendering,
the objects being drawn are culled or sorted before they are given to each of the graphics cards.
The sort-last rendering technique used by the Library is very flexible and powerful. It can do the
following:
• Create very large images.
• Process very large datasets.
• Work with either distributed or shared memory systems.
• Render volumetric data.
• Be extended to support new compositing operators.
The extensible implementation of the Library makes it possible for it to work on a variety of
platforms and graphics cards as well as take advantage of new networking technologies.
1.3 Library Entities
This section describes a set of Library-specific entities that are key to understanding how the
Library works.
1.3.1 Application
An application is one or more programs that run on one or more computers that use the Library
to create images. In some cases, all the programs may run on a single computer; in other cases,
the programs may be distributed across multiple computers. From the point of view of the
Library, all these programs can create a session and then manipulate this session to do useful
work.
1.3.2 System
A system is a computer and operating system environment that is capable of running one or
more programs.
1.3.3 Session
A session is the Library entity that connects all the programs in an application. A session is
identified by a property known as a sessionID. All programs that make up an application
create a session by specifying the same sessionId. A program can be a part of only one session
at a time.
1.3.4 Host
It is best to think of a host as a thread of execution. A host differs from a program in that a
program can have more that one host. To contribute images to frames, a program must have at
least one host.
A host has a unique identifier that consists of two parts:
12 Main Areas of the Parallel Compositing Library