Database Reference
In-Depth Information
A
B
Read
Data
Desktop
Isosurface
Desktop
Render
Desktop
Display
C
D
E
F
8PE Cluster
Isosurface
8PE Cluster
Render
Network transfer (C and F)
Disk read
Shared memory transfer
Desktop only pipeline
Cluster isosurface pipeline
Cluster render pipeline
Figure 9.1
(See color insert following page 224.) This image shows three dif-
ferent partitionings of a simple visualization pipeline consisting of four stages:
data I/O, computing an isosurface, rendering isosurface triangles, and image
display. In one partitioning, all operations happen on a single desktop machine
(A-B, blue background). In another, data is loaded onto an eight-processor
cluster for isosurface processing, and the resulting isosurface triangles are sent
to the desktop for rendering (D-C-B, yellow background). In the third, data is
loaded onto the cluster for isosurface processing and rendering, and the result-
ing image is sent to the desktop for display (D-E-F, magenta background).
high-performance visualization for many problem domains is more toward this
latter configuration, which exhibits favorable scaling characteristics as data
sizes grow larger.
In the case when all rendering occurs on the desktop, all data represen-
tation and data transfer issues are encapsulated inside the graphics library
(though there may be substantial SDM issues to consider in the visualization
pipeline prior to the rendering stage). In the case where rendering occurs on
one machine and image pixels are transmitted to one or more remote ma-
chines for viewing, several interrelated issues appear: security (authorization
and authentication), compression (lossless vs. lossy), ecient data movement
(lossless vs. lossy, multistreamed, multicast), data formats, and models for the
pixel data.
For this latter issue, a widely adopted approach is the remote framebuffer
protocol (RFB), which is part of the popular virtual network computing
(VNC) client/server application for remote desktop access.
15
Here, the re-
mote client connects to a central server where the data-intensive application
is run; the resulting imagery is “harvested” by the VNC server, encoded into
RFB format, and transmitted to the VNC client for display via a standard
transmission control protocol (TCP) connection. In its native form, VNC is
not capable of capturing image pixels created by graphics hardware. Other
