Chummer supports a handful of optional rules found throughout the sourcebooks. Optional rules can be turned on by selecting the Optional Rules tab in the Options
window. This page describes what each of the optional rules does within Chummer.
More Lethal Gameplay (SR4 75)
This option increases the DV of all Weapons by 2. See SR4A 75.
No Armor Encumbrance when wearing only one piece of Armor (AR 44)
When this option is enabled, characters ignore the effects of Armor Encumbrance if they only have a single piece of Armor equipped. See AR 44 (Tweaking Armor Encumbrance).
Limit Skills to 20 dice or 2 x (Natural Attribute + Skill Rating), whichever is higher (SR4 61)
This option limits the size of an Active Skill's dice pool to either 20 dice, or twice the Skill's Natural Attribute + Rating. See SR4A 61 (Dice Pool Modifiers).
Allow Skills to be re-Grouped if all Ratings are the same (SR4 FAQ)
When this option is enabled, characters are allowed to increase a Skill Group's Rating if all of the Active Skills that make up that Group have been changed to have the same Rating again.
As described in the SR4 FAQ:
Can you regain a skill group if each of the component skills are raised to the same level?
With the gamemaster's permission if a skill group's individual skills are raised to the same rating, and there are no specializations in any of those skill, then those skills can be treated as a skill group from that point on.
Metatypes cost Karma equal to their BP
When this option is enabled, a character's Metatype costs them an amount of Karma equal to its BP. This is a rule that was printed in the German version of the books but was never applied to the English versions.
High Strength affects Weapon Recoil (AR 163)
This option decreases a character's Recoil penalty when their Strength is 6 or higher. See AR 163 (Recoil and Strength).
Use Maximum Armor Modifications (AR 44)
This option enables the Maximum Armor Modifications rule (see AR 44). When enabled, Armors that do not have a Capacity Rating will calculate one that is used to determine the amount of Gear and Armor Modification plugins they may have.
Use Armor Suit Capacity (AR 44)
This option enables the Armor Suit Capacity rule (see AR 44). When enabled, Gear and Armor Mods added to Armor Suits that have a Capacity Rating will consume Capacity.
Allow Armor Degradation (AR 44)
This option enables the Armor Degradation rule (see AR 44). When enabled, Armors will show a + and - button next to each Rating to damage or repair them.
Use calculated Vehicle Sensor Ratings (AR 105)
When this optional rule is enabled, a Vehicle's Sensor Rating is calculated as the average Rating for all of its Sensors instead of using the fixed Sensor Rating found in its Vehicle entry.
Use alternate Matrix Attribute (UN 39)
When this optional rule is enabled, Technomancers can choose which Attribute to use for each Test when on the Sprites and Complex Forms tab instead of using the one recommended by the Complex Form.
Use alternate Complex Forms costs (UN 39)
When this optional rule is enabled, all Complex Forms cost the same amount of BP/Karma as Spells and Complex Form Ratings are disabled. Complex Form Options remain at their standard cost.
Allow any Bioware to be converted to Trasgenic (AU 93)
When this optional rule is enabled, any Bioware can be forced into the Genetech: Transgenics category with GM approval.
Allow Skill Groups to be broken during character creation (SR4 68)
When this optional rule is enabled, characters will be able to break Skill Groups while in Create Mode by clicking the Break button on the Skill.
Allow any Detection Spell to be taken as Extended range version (SM 165)
When this optional rule is enabled, the Extended versions of Spells are no longer shown in the Spell list. Instead, an Extended version of each Detection Spell can now be selected by checking the Extended Spell checkbox. If this optional rule is disabled, the Extended versions of the Spells still appear in the list as normal.