Game Development Reference
for the remaining 90%. Multiply the inverted usages for flows 5, 7, and 12 by 0.9
(90%) to account for that. The final result for flow 5 is 0.574 (57.4%), for flow 7 is
0.038 (3.8%), and for flow 12 is 0.287 (28.7%). Figure 12.25 shows these numbers
included with the results for the other flows usages calculated so far.
Figure 12.25 Inverted usage added for
Figure 12.24 Inverted usage added
for flows leaving
Go to the next state, which is NoPointsHaveItem . This is another situation with only two
flows to invert. Swap the usage values for flow 8 and flow 9. Figure 12.26 shows flow
8 added to the table with a 90% inverted usage and flow 9 with a 10% inverted usage.
NoPointsItemUnlocked is the last state to account for on the diagram. Three flows leave
this state, so you have to do some calculations. Flow 10 has a 5% usage, so its recipro-
cal is 20. Flow 11 has a 90% usage. Its reciprocal is 1.11. Flow 13 has the same usage
as flow 10 and, therefore, the same reciprocal of 20. Now do step 2 and add up the rec-
iprocals. 20 +1.11 +20 = 41.11. Find the inverted usage of each flow by dividing their
reciprocals by this total. For flows 10 and 13, calculate 20/41.11, which results in 0.486,
or 48.6%. Calculate flow 11's inverted usage as 1.11/41.11, which is 0.027, or 2.7%.
Enter these values to the table to get the completed version shown in Figure 12.27.
With these inverted percentages you can produce TFD Cleanroom paths and test cases
in the same way you did earlier from the normal usage probabilities.