Modifying GURPS combat using Pocket Universe Rules?

thom · 11-09-2015, 09:29 AM

So my GURPS game crashed & burned a while back primarily because my players hated all the die rolling during combats. Recently I ran across the Unigames Pocket Universe rules, which are similar to GURPS (but using 2D10 vs. 3D6), and I noticed its combat system uses a take the defender's skill level, subtract ten from it and that becomes his Defense Score. The Defense Score becomes a modifier to the attacker's skill level, and then we just roll once to see if the attacker succeeds. This basically cuts the number of combat rolls in half!

example: a character has sword-14, shield-13, Dodge-11, and is using a medium shield (+2), his Defense Scores would be:
sword 14 -9 = 5 Parry
shield 13 (+2 for shield) - 9 = 6 Block
Dodge 11 -9 = 2 Dodge

And so when attacked, he chooses which Defense to use, and the attacker subtracts that number from his weapon skill and rolls to see if his attack succeeds.

So I'm wondering how (if) this mechanic would work for combat in GURPS.
* If one subtracts 10 from a 2D10 skill-based roll, would subtracting 9 from a 3D6 system be roughly equivalent (I'm thinking 10 is one-half of 20, so 9 would be one-half of 18)?
* Dodge would become another skill based on Dexterity that could be raised normally; shields would only add a bonus to a character's Shield Block skill, and weapon parries would stay the same (base skill -9 to to determine the Parry Defense Score).
* Then I would need to compare how quickly attack skills rise vs. defense skills to see if all this stays roughly equal.

So, combat number-crunching gurus; :) how does this concept look? Is it workable? I'm pretty sure if I were really able to cut the number of combat rolls in half, my players would be interested in trying GURPS again-they liked most of the rules.

Thanks for any advice!

thom

Varyon · 11-09-2015, 10:34 AM

With the way 3d6 scales, the actual probability of a hit scales in a complex way depending on the skill levels of each character involved. If the attacking character has skill 16, you get a good approximation by subtracting 4 from the defender's defense score and applying that as a penalty. For an attacker with skill 15, you instead need to subtract around 5 from the defense score.

Here's a table. The x axis is the defender's score, the y is the attacker's score, and the table itself is what the effective score would be.

Code:

		5	6	7	8	9	10	11	12	13	14	15	16
													
5		5	5	5	5	5	5	4	4	4	4	4	4
6		6	6	6	6	6	5	5	4	4	4	4	4
7		7	7	7	7	6	6	5	5	5	4	4	4
8		8	8	8	8	7	7	6	5	5	4	4	4
9		9	9	8	8	8	7	7	6	5	5	4	4
10		10	10	9	9	8	8	7	6	6	5	4	4
11		11	10	10	10	8	8	8	7	6	5	5	4
12		12	11	11	10	10	9	8	7	6	5	5	4
13		13	12	12	12	10	9	8	8	7	6	5	4
14		13	13	12	12	10	10	9	8	7	6	5	4
15		14	13	13	12	11	10	9	8	7	6	5	4
16		15	14	13	12	11	10	9	8	7	6	5	4

Note the lowest it ever goes is 4, because that's always as Success (Critical Success, even).

The way I'd do it, I'd have whoever had the better score be the one who actually rolls. From this, subtract the score of the other character, and add 6. Defense will usually be the lower of the two, so using the defender's defense score -6 as the penalty should work. For your example character, he normally has Parry 12, Block 11, and Dodge 13, so he would instead impose a -6, -5, or -7, respectively. If you want to go off the character's skill, that -6 is appropriate for (skill/2+3), meaning using Skill -9 would indeed give comparable results. For determining Dodge "skill," you'd use Basic Speed x2. Note, however, that this means the DB from shields should be doubled. In fact, all defense bonuses - from Combat Reflexes, Enhanced Defenses, and so forth - should be doubled and turned into a penalty for the attacker, while defense penalties should be doubled and turned into a bonus for the attacker.

thom · 11-09-2015, 11:49 AM

::channeling Keanu Reeves:: Whoa! ;)

Pretty cool analysis Varyon! It seems this concept might work...

I'm a bit fuzzy why you think the various defense bonuses should be doubled though? Keep in mind, under this rules alternative shields only add a defense bonus to the character's Shield Block skill, not to all his combat skills. Does that change anything with your numbers?

Varyon · 11-09-2015, 12:14 PM

I miscalculated in my previous post. I estimated it as skill/2+3-6 being equivalent to skill-9, but those are only equivalent at skill=12. Above this, skill-9 gives too much of a penalty; below this, it gives too small of one. Since you have to do some calculation anyway, and your players' complaints appear to be about too many rolls, use Skill/2-3 (or Basic Speed -3 for Dodge) instead.

The reason I suggested doubling all defense bonuses/penalties is because defenses scale using skill/2, while my suggestion was scaling by skill. Something that is +1 to skill/2 would functionally be +2 to skill to be equivalent. This is unnecessary to account for, however, because you need to base things off skill/2 to avoid too much departure from RAW.

As an example of how my values were off, consider a character with Shield 14, Combat Reflexes (+1 all defenses), and a Medium Shield (+2 DB). He'd normally have Block 13, which would be comparable to a -7 to his enemy's attacks. Using Skill -9, he'd cause a base of -5, which would boost to a ridiculous -11 when accounting for Combat Reflexes and DB. Not doubling those would mean only -8, which is fairly close to what it "should" be, but you'll get further off the higher the character's skill is. Skill/2-3, however, should always keep you close to the probabilities that would be in play you were rolling for both attack and defense.

Maz · 11-09-2015, 12:55 PM

I have done this as well for mooks in my DF game. I did a lot of calculations and also ended up with an "good enough to use" number that was "their defense -6". Much like Varyon.

So a mook with Parry-10 would give a -4 penalty.
Mooks never took advanced actions such as retreating dodge or parry. You can't use Telegraphic attack against them, for obvious reasons.

Mooks that would normally All-out attack, such as zombies. Simply give a +4 bonus to hit them.

I had bosses use all the normal rules. This way a boss also feels a lot more special.

Varyon · 11-09-2015, 01:08 PM

Quote:

Originally Posted by Maz

You can't use Telegraphic attack against them, for obvious reasons.

This is an important bit to note. I didn't mention Deceptive Attack because it's unnecessary to make any note of (Deceptive Attack would result in you being less likely to hit), but I forgot about Telegraphic Attack (which by the numbers would result in you getting a net bonus of +2).

If Telegraphic Attack would normally be an option, just say that an enemy who cannot defend gives a +4 to any attack, and his Defense Score doesn't apply. Alternatively, and more cinematically, have attacking such a foe get a +10 to attack, but his Defense Score does apply. Thus, a foe who would normally have Parry 12 (-6 to hit) is targeted at +4, while a master duelist who would normally have Parry 20 (-14 to hit) is targeted at -4.

If you want to be a bit more complex, have any attack that would have missed without accounting for Defense Score automatically "whiff" (that is, miss outright), not using up any of the defender's defenses.

Infornific · 11-09-2015, 01:57 PM

Doing a one roll system is a bit tricky. The practical effect of Pocket Universe's system is that for one character to hit another equally skilled character, he needs to roll 10 or less on 2d10, a 45% chance. This is true regardless of how high or low skills are. Oddly enough GURPS has a similar base hit probability. As it stands in GURPS melee combat two opponents of roughly equal skill have close to a 50/50 chance of hitting each other. For example, if both have Skill 14 and Parry 10 the chance of hitting is around 45% - 90% chance of a successful attack * 50% chance of a failed parry. For higher skills, the defense rolls become close to automatic - e.g., two fighters with skills of 20 and Parrys of 13 will hit almost automatically but will also parry over 80% of the time and thus have a lower chance of hitting. So they both might use Deceptive Attack and bring things back to 14 vs 10 and our near even chance of a hit. It can get more complicated but for basic combat it makes sense for high skill characters to either Feint or make Deceptive Attacks to improve their chances of hitting.

Now if you use one roll and base it off of Attack and Parry as they exist, you'll mess up the existing balance. Since defenses increase at half the rate of offenses, with higher skill offense dominates. Let's take our example above and assume we're basing our Parry modifier on the base parry - 6. So the skill 14, Parry 10 fighter will get a -4 penalty to hit each other and roll against a base 10. But the skill 20 fighter will get a -7 to hit each other and roll against a base 13 to hit.

One option is to simply use full skill - the attack roll is 10 plus the attack skill minus Parry, with Parry equal to the defender's skill. Dodge would be Speed*2 rather than Speed +3 in this system. Note that differences in skill will have a greater influence on who hits or fails to hit and thus a small difference in skill will be more decisive than in standard GURPS.

Alternately, make the Attack roll equal to 10 + Attack Skill/2 - Defense Skill/2. Dodge in this system would default to Speed (seems like old times.) Defense Bonus for shields should be halved, or alternately added to the appropriate skill before halving. This would preserve the current relative value of skill though it would make even levels of skill more important. It depends on how you feel about break points. For ranged attacks, I would apply ranged penalties to base skill and then halve it.

Varyon · 11-09-2015, 02:15 PM

My analysis didn't account for Deceptive Attacks or Telegraphic Attacks, but I think Infornic's observation of typically having around a 50% chance with equal skill is probably about right. You'll see some variation, but probably not enough to be too terribly significant. That gives a very simple (10-skill) as the character's Defense Score (that is, the penalty they impose on enemy attacks), with Dodge using Basic Speed x2. As I noted before, you'll want to double any stated penalties/bonuses, as those were based on skill/2. For example, a Broadsword 14 character should expect to have the same chance of hitting a character with Shield 10 and a Medium Shield (Block 10) as a fellow Broadsword 14 character (Parry 10) or a character with Basic Speed 6 and Combat Reflexes (Dodge 10).

Note a character can have a poor enough Defense Score to give foes a bonus to hit him. So long as it isn't more than a +4 (for skill 6 or speed 3), however, it's not much different from a low skill foe being Telegraphic Attack fodder.

thom · 11-10-2015, 12:42 PM

Quote:

Originally Posted by Infornific

One option is to simply use full skill - the attack roll is 10 plus the attack skill minus Parry, with Parry equal to the defender's skill. Dodge would be Speed*2 rather than Speed +3 in this system. Note that differences in skill will have a greater influence on who hits or fails to hit and thus a small difference in skill will be more decisive than in standard GURPS.

Alternately, make the Attack roll equal to 10 + Attack Skill/2 - Defense Skill/2. Dodge in this system would default to Speed (seems like old times.) Defense Bonus for shields should be halved, or alternately added to the appropriate skill before halving. This would preserve the current relative value of skill though it would make even levels of skill more important. It depends on how you feel about break points. For ranged attacks, I would apply ranged penalties to base skill and then halve it.

Aha! This is what I was originally considering doing-I just didn't say it correctly. I.e. all Defenses are calculated at full skill level, so if a character has a Shield skill at 14, his Block Defense Score is (14 -9) = 5; not (14/2+3)-9 = 1.

But I agree this might overemphasize small differences. ::sigh::

11-09-2015, 09:29 AM	#1
thom Join Date: Oct 2011	Modifying GURPS combat using Pocket Universe Rules? So my GURPS game crashed & burned a while back primarily because my players hated all the die rolling during combats. Recently I ran across the Unigames Pocket Universe rules, which are similar to GURPS (but using 2D10 vs. 3D6), and I noticed its combat system uses a take the defender's skill level, subtract ten from it and that becomes his Defense Score. The Defense Score becomes a modifier to the attacker's skill level, and then we just roll once to see if the attacker succeeds. This basically cuts the number of combat rolls in half! example: a character has sword-14, shield-13, Dodge-11, and is using a medium shield (+2), his Defense Scores would be: sword 14 -9 = 5 Parry shield 13 (+2 for shield) - 9 = 6 Block Dodge 11 -9 = 2 Dodge And so when attacked, he chooses which Defense to use, and the attacker subtracts that number from his weapon skill and rolls to see if his attack succeeds. So I'm wondering how (if) this mechanic would work for combat in GURPS. * If one subtracts 10 from a 2D10 skill-based roll, would subtracting 9 from a 3D6 system be roughly equivalent (I'm thinking 10 is one-half of 20, so 9 would be one-half of 18)? * Dodge would become another skill based on Dexterity that could be raised normally; shields would only add a bonus to a character's Shield Block skill, and weapon parries would stay the same (base skill -9 to to determine the Parry Defense Score). * Then I would need to compare how quickly attack skills rise vs. defense skills to see if all this stays roughly equal. So, combat number-crunching gurus; :) how does this concept look? Is it workable? I'm pretty sure if I were really able to cut the number of combat rolls in half, my players would be interested in trying GURPS again-they liked most of the rules. Thanks for any advice! thom

11-09-2015, 10:34 AM	#2
Varyon Join Date: Jun 2013	Re: Modifying GURPS combat using Pocket Universe Rules? With the way 3d6 scales, the actual probability of a hit scales in a complex way depending on the skill levels of each character involved. If the attacking character has skill 16, you get a good approximation by subtracting 4 from the defender's defense score and applying that as a penalty. For an attacker with skill 15, you instead need to subtract around 5 from the defense score. Here's a table. The x axis is the defender's score, the y is the attacker's score, and the table itself is what the effective score would be. Code: 5 6 7 8 9 10 11 12 13 14 15 16 5 5 5 5 5 5 5 4 4 4 4 4 4 6 6 6 6 6 6 5 5 4 4 4 4 4 7 7 7 7 7 6 6 5 5 5 4 4 4 8 8 8 8 8 7 7 6 5 5 4 4 4 9 9 9 8 8 8 7 7 6 5 5 4 4 10 10 10 9 9 8 8 7 6 6 5 4 4 11 11 10 10 10 8 8 8 7 6 5 5 4 12 12 11 11 10 10 9 8 7 6 5 5 4 13 13 12 12 12 10 9 8 8 7 6 5 4 14 13 13 12 12 10 10 9 8 7 6 5 4 15 14 13 13 12 11 10 9 8 7 6 5 4 16 15 14 13 12 11 10 9 8 7 6 5 4 Note the lowest it ever goes is 4, because that's always as Success (Critical Success, even). The way I'd do it, I'd have whoever had the better score be the one who actually rolls. From this, subtract the score of the other character, and add 6. Defense will usually be the lower of the two, so using the defender's defense score -6 as the penalty should work. For your example character, he normally has Parry 12, Block 11, and Dodge 13, so he would instead impose a -6, -5, or -7, respectively. If you want to go off the character's skill, that -6 is appropriate for (skill/2+3), meaning using Skill -9 would indeed give comparable results. For determining Dodge "skill," you'd use Basic Speed x2. Note, however, that this means the DB from shields should be doubled. In fact, all defense bonuses - from Combat Reflexes, Enhanced Defenses, and so forth - should be doubled and turned into a penalty for the attacker, while defense penalties should be doubled and turned into a bonus for the attacker.

11-09-2015, 11:49 AM	#3
thom Join Date: Oct 2011	Re: Modifying GURPS combat using Pocket Universe Rules? ::channeling Keanu Reeves:: Whoa! ;) Pretty cool analysis Varyon! It seems this concept might work... I'm a bit fuzzy why you think the various defense bonuses should be doubled though? Keep in mind, under this rules alternative shields only add a defense bonus to the character's Shield Block skill, not to all his combat skills. Does that change anything with your numbers?

11-09-2015, 12:14 PM	#4
Varyon Join Date: Jun 2013	Re: Modifying GURPS combat using Pocket Universe Rules? I miscalculated in my previous post. I estimated it as skill/2+3-6 being equivalent to skill-9, but those are only equivalent at skill=12. Above this, skill-9 gives too much of a penalty; below this, it gives too small of one. Since you have to do some calculation anyway, and your players' complaints appear to be about too many rolls, use Skill/2-3 (or Basic Speed -3 for Dodge) instead. The reason I suggested doubling all defense bonuses/penalties is because defenses scale using skill/2, while my suggestion was scaling by skill. Something that is +1 to skill/2 would functionally be +2 to skill to be equivalent. This is unnecessary to account for, however, because you need to base things off skill/2 to avoid too much departure from RAW. As an example of how my values were off, consider a character with Shield 14, Combat Reflexes (+1 all defenses), and a Medium Shield (+2 DB). He'd normally have Block 13, which would be comparable to a -7 to his enemy's attacks. Using Skill -9, he'd cause a base of -5, which would boost to a ridiculous -11 when accounting for Combat Reflexes and DB. Not doubling those would mean only -8, which is fairly close to what it "should" be, but you'll get further off the higher the character's skill is. Skill/2-3, however, should always keep you close to the probabilities that would be in play you were rolling for both attack and defense.

11-09-2015, 12:55 PM	#5
Maz Join Date: Aug 2005 Location: Denmark	Re: Modifying GURPS combat using Pocket Universe Rules? I have done this as well for mooks in my DF game. I did a lot of calculations and also ended up with an "good enough to use" number that was "their defense -6". Much like Varyon. So a mook with Parry-10 would give a -4 penalty. Mooks never took advanced actions such as retreating dodge or parry. You can't use Telegraphic attack against them, for obvious reasons. Mooks that would normally All-out attack, such as zombies. Simply give a +4 bonus to hit them. I had bosses use all the normal rules. This way a boss also feels a lot more special.

11-09-2015, 01:57 PM	#7
Infornific Join Date: Dec 2004	Re: Modifying GURPS combat using Pocket Universe Rules? Doing a one roll system is a bit tricky. The practical effect of Pocket Universe's system is that for one character to hit another equally skilled character, he needs to roll 10 or less on 2d10, a 45% chance. This is true regardless of how high or low skills are. Oddly enough GURPS has a similar base hit probability. As it stands in GURPS melee combat two opponents of roughly equal skill have close to a 50/50 chance of hitting each other. For example, if both have Skill 14 and Parry 10 the chance of hitting is around 45% - 90% chance of a successful attack * 50% chance of a failed parry. For higher skills, the defense rolls become close to automatic - e.g., two fighters with skills of 20 and Parrys of 13 will hit almost automatically but will also parry over 80% of the time and thus have a lower chance of hitting. So they both might use Deceptive Attack and bring things back to 14 vs 10 and our near even chance of a hit. It can get more complicated but for basic combat it makes sense for high skill characters to either Feint or make Deceptive Attacks to improve their chances of hitting. Now if you use one roll and base it off of Attack and Parry as they exist, you'll mess up the existing balance. Since defenses increase at half the rate of offenses, with higher skill offense dominates. Let's take our example above and assume we're basing our Parry modifier on the base parry - 6. So the skill 14, Parry 10 fighter will get a -4 penalty to hit each other and roll against a base 10. But the skill 20 fighter will get a -7 to hit each other and roll against a base 13 to hit. One option is to simply use full skill - the attack roll is 10 plus the attack skill minus Parry, with Parry equal to the defender's skill. Dodge would be Speed*2 rather than Speed +3 in this system. Note that differences in skill will have a greater influence on who hits or fails to hit and thus a small difference in skill will be more decisive than in standard GURPS. Alternately, make the Attack roll equal to 10 + Attack Skill/2 - Defense Skill/2. Dodge in this system would default to Speed (seems like old times.) Defense Bonus for shields should be halved, or alternately added to the appropriate skill before halving. This would preserve the current relative value of skill though it would make even levels of skill more important. It depends on how you feel about break points. For ranged attacks, I would apply ranged penalties to base skill and then halve it.

11-09-2015, 02:15 PM	#8
Varyon Join Date: Jun 2013	Re: Modifying GURPS combat using Pocket Universe Rules? My analysis didn't account for Deceptive Attacks or Telegraphic Attacks, but I think Infornic's observation of typically having around a 50% chance with equal skill is probably about right. You'll see some variation, but probably not enough to be too terribly significant. That gives a very simple (10-skill) as the character's Defense Score (that is, the penalty they impose on enemy attacks), with Dodge using Basic Speed x2. As I noted before, you'll want to double any stated penalties/bonuses, as those were based on skill/2. For example, a Broadsword 14 character should expect to have the same chance of hitting a character with Shield 10 and a Medium Shield (Block 10) as a fellow Broadsword 14 character (Parry 10) or a character with Basic Speed 6 and Combat Reflexes (Dodge 10). Note a character can have a poor enough Defense Score to give foes a bonus to hit him. So long as it isn't more than a +4 (for skill 6 or speed 3), however, it's not much different from a low skill foe being Telegraphic Attack fodder.