1. First steps in Reaktor Core - Native Instruments

5.6. Other bad numbers
Denormal numbers are not the only kind that can cause problems in Reaktor
Core structures with internal states, and particularly in feedback loops. Other
examples include INFs, NaNs and QNaNs. We are not going to discuss those
in detail here, because that information is available in other places, including
the Internet. What’s important for us is preventing those kinds of numbers
from appearing in our structures.
Generally, such numbers appear as the result of invalid operations. Division
by zero is the easiest case. Other cases involve numbers getting too large to
fit in the floating point representation (that would be above 10 38 in absolute
magnitude), or outside the reasonable range for a particular operation.
Such numbers tend to get stuck inside structures, and in a way they are more
sticky than denormals. For example as soon as you add a denormal value to
another value which is not denormal, the result will be non-denormal (unless
the other value is also very small and close to being a denormal). On the other
hand if you add a normal value to an INF, the result will still be an INF.
Besides having a tendency to stick in structures forever (or better said, until
the structure is reset), these numbers also have a bad habit of requiring much
larger processing times on some CPUs. Therefore you should do your best to
prevent them from being created at all. That means, for example, that whenever
you divide two numbers you ensure that the denominator (the bottom part of
the fraction) is not zero. The case of initialization requires particular attention
here. For example, consider the following structure element:
If for whatever reason, the initialization event does not come on the lower
input of the Divider module, a division by zero will happen during initialization
processing. In this case you might consider using a modulation delay macro
instead, or depending on your particular needs find another solution.
5.7. Building a 1-pole low pass filter
A simple 1-pole low pass filter can be built using a recursive equation:
y=b*x+(1-b)*y -1
where
x is the input sample,
y is the new output sample,
y -1 is the previous output sample, and
b is the coefficient defining the filter’s cutoff.
REAKTOR CORE – 101