HP Scalable Visualization Array Software - Manual (Page 20)

• Multiple displays with different resolutions.
• Use of a variable number of display and render nodes to solve the computational and
rendering requirements of an application.
• Bounded configuration designed for a single user.
• Larger, modular, expandable systems designed for one or more concurrent users.
See Chapter 3 for more information on the physical configurations of the SVA.
2.3 SVA Operation
This section describes a common way data flows through an SVA.
2.3.1 Cluster Data Flow
Figure 2-1 shows a high-level view of the basic components of an SVA.
Figure 2-1 SVA Data Flow Overview
OpenGL Graphics
User Application
Master Node
user interface
transfer simulation data
and drawing commands
display nodes
System Interconnect
Card
OpenGL Graphics
Card
OpenGL Graphics
Card
OpenGL Graphics
Card
multi-tile display
render nodes
OpenGL Graphics
Card
OpenGL Graphics
Card
OpenGL Graphics
Card
A common usage scenario includes a master application node that runs the controlling logic of
an application, processes the 3D data, and updates the virtual display or scene in the case of
scenegraph applications. The master node typically does no rendering. Because it transmits data
changes to other visualization nodes, it must be able to communicate with these nodes using the
cluster SI. The SI is the fastest network available to the SVA and is the best choice for internode
communication when performance is important.
A different scenario does not use a master application node. Instead, an application relies on
Distributed Multi-Head X (DMX) to distribute the display output to multiple nodes and displays.
It does this by controlling the back-end X Servers running on each of the display nodes. Partial
images routed to individual display devices are assembled and displayed as a single virtual
image.
Other scenarios arise depending on the application and the capabilities of visualization
middleware running on the SVA. For example, several render nodes can carry out rendering
and compositing tasks. The render nodes can rely on middleware software to handle the
compositing of any partial images. The image data then flows to a display node before being
sent to a display device or remote node, for example; a desktop display outside the SVA.
See Chapter 6 for other usage scenarios.
2.3.2 File Access
Visualization applications typically read data from files in response to user input. For example,
after starting an application, you specify a data file to open and load. Without exiting the
application, you can select additional data files to open and load, replacing or adding to the data
already loaded. Much visualized data is static rather than time-varying. When visualizing
time-varying data, the application must read and cache multiple time steps. The application may
not be able to visualize the data as it is being read. Each time step may need to be analyzed and
20 SVA Architecture