Linear Model Analysis of Real-Time Rendering - Real-Time Rendering: Computer Graphics with Control Engineering - page 40

+
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370

PID(z)

n4s2

Scope

Constant

Subtract

Discrete PID
Controller

Idmodel

FIGURE 3.15 (See colour insert.) SISO control system in Experiment 3.

Simulated Reference Tr acking with Controller

400

350

300

250

200

150

100

50

Reference
Controlled Output

0

0 0.5 1 1.5 2 2.5 3

×10 4

Frame

FIGURE 3.16 Simulated reference tracking with PID controller.

on a different computer and communicated with the rendering process via a network
link using the transmission control protocol (TCP). The purpose of such a modi-
fied design was to avoid the interference and loading of the rendering process from
MATLAB computation. The output of this experiment is shown in Figure 3.17.
Note from Figure 3.17 that the actual rendering application tracks the pre-defined
reference level accurately as in the previous case. The steady-state error is negligible
(less than 1% of the reference value), further reinforcing the validity of our system
model and control framework.

3.7 DISCUSSION

One challenge we faced in this research was the stability of frame rates during data
collection. We noted that frame rates on certain computers fluctuated even with-
out changes in input geometry or user-controlled events such as mouse movement