a blog of short and medium length ttrpg thinking posts

Wednesday, March 25, 2020

dice pools

Postulated: dice pools are fun. It is fun to adjust the number of dice you roll. It's scary to face a roll with fewer dice than usual, and feels great to roll a huge fistful.

Postulated: forgone conclusions are not fun. If you know before you roll the dice that there's no way to get a certain outcome, why roll?

Proposed: this is why people don't like taking sums of dice pools.

The fact that the floor of the sum of a dice pool shifts is problematic in a different way than that the peak of its bell curve shifts or than that its ceiling shifts. Look at the probability of rolling a certain sum or greater on 1-4 dice:

#1D2D3D4D
1100.00%
283.30%100.00%
366.70%97.20%100.00%
450.00%91.70%99.50%100.00%
533.30%83.30%98.10%99.90%
616.70%72.20%95.40%99.60%
758.30%90.70%98.80%
841.70%83.80%97.30%
927.80%74.10%94.60%
1016.70%62.50%90.30%
118.30%50.00%84.10%
122.80%37.50%76.10%
1325.90%66.40%
1416.20%55.60%
159.30%44.40%
164.60%33.60%
171.90%23.90%
180.50%15.90%
199.70%
205.40%
212.70%
221.20%
230.40%
240.10%

The floor moving is bad because it creates forgone conclusions by opening gaps in the outcome range of the smaller dice pools. It also creates them by shifting the 100% to outcomes that had previously not been 100%. We don't see either of those problems when we subtract the number of dice rolled from the sum:

#1D2D3D4D
0100.00%100.00%100.00%100.00%
183.30%97.20%99.50%99.90%
266.70%91.70%98.10%99.60%
350.00%83.30%95.40%98.80%
433.30%72.20%90.70%97.30%
516.70%58.30%83.80%94.60%
641.70%74.10%90.30%
727.80%62.50%84.10%
816.70%50.00%76.10%
98.30%37.50%66.40%
102.80%25.90%55.60%
1116.20%44.40%
129.30%33.60%
134.60%23.90%
141.90%15.90%
150.50%9.70%
165.40%
172.70%
181.20%
190.40%
200.10%

This also makes the tiers of possible outcomes go up by 5s which is a lot easier to deal with mentally than going up by 6s (unless you're Count Rugen).

a modest proposal

Take the sixes off your dice and replace them with zeroes. Boom, done.




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