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Old 07-22-2021, 07:58 AM   #31
Acala
 
Join Date: Sep 2019
Default Re: combat without actual defense rolls?

Gollum, your rule is used in a Brazilian RPG called Daemon System. Its a percentege system, going all the way to 100% skill level. When combat happens, the attacker uses his skill, ( lets say, 80%), adds 50%, then subtracts the defender skill ( lets say, 60%). So in this case, the attacker would have 80+50-60 = 70%. This means that if he rolls under 70, he hits, if he rolls over, the defender hits him. So in one roll, the action was resolved and something actually happened, there is no useless roll. Mind you, a roll under 5% is a critical, and a roll over 95% is a critical failure, so if someone gets 0% chance, he always has a chance if he rolls under 5%.

As you can see, your rule works basically the same in GURPS, which i think is spot on. Of course, might not please everyone, but it works. It works for this other system and it would work in yours.
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Old 07-29-2021, 04:10 AM   #32
Dralnu
 
Join Date: Jul 2021
Default Re: combat without actual defense rolls?

Quote:
Originally Posted by ericbsmith View Post
Actually, that in itself is a wonderful mechanic, elegantly handling the problem of player influence, no matter how you ultimately decide to calculate the attack/defense combo roll.

I will note that any arbitrary skill roll can be flipped easily by using [20-skill]; what I mean by that is if an attack is going to succeed on a roll of 12 or less that means it fails on a roll of [20-12]=8 or less. This way you can use whatever method you like to calculate attack skill and then "flip" the roll to give it to the player rather than having the GM roll it.

I don't particularly like these rules, because they do drastically and fundamentally change the chances of success - especially when you get up past 20 skill - but there are plenty of other methods of breaking down an attack/defense into a single roll.

On my website I have a Combat Chance of Success Table, which gives the percentage chance of an attack succeeding (including critical successes) for any given attack and defense between 4 & 16. Using that same table it wouldn't be hard to assign an "attack number" to each percentage chance. For skills above 16 simply use the Deceptive Attack rule (-2 attack, -1 defense) to bring the score down to below 16 somewhere (usually a score of 12-13 is the "sweet spot" for attack rolls).

Doing that yields this table:
Code:
Defense  Attack ->
   \/     5   6   7   8   9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30
      5   4   5   6   7   8   9  10  11  12  13  14  14  15  15  15  15  15  15  15  15  15  15  15  15  15  15    
      6   4   5   6   7   8   9  10  11  12  12  13  13  14  14  15  15  15  15  15  15  15  15  15  15  15  15    
      7   4   5   6   7   8   9  10  10  11  12  12  12  13  13  14  14  15  15  15  15  15  15  15  15  15  15    
      8   4   5   6   7   8   9   9  10  11  11  11  12  12  12  13  13  14  14  15  15  15  15  15  15  15  15    
      9   4   5   6   7   7   8   9   9  10  10  10  11  11  12  12  12  13  13  14  14  15  15  15  15  15  15    
     10   4   5   5   6   7   8   8   9   9   9  10  10  10  11  11  12  12  12  13  13  14  14  15  15  15  15    
     11   4   5   5   6   6   7   7   8   8   8   9   9  10  10  10  11  11  12  12  12  13  13  14  14  15  15    
     12   4   4   5   5   6   6   7   7   7   7   8   8   9   9  10  10  10  11  11  12  12  12  13  13  14  14    
     13   4   4   4   5   5   6   6   6   6   7   7   7   8   8   9   9  10  10  10  11  11  12  12  12  13  13    
     14   4   4   4   4   5   5   5   5   6   6   6   7   7   7   8   8   9   9  10  10  10  11  11  12  12  12    
     15   4   4   4   4   4   4   5   5   5   5   5   6   6   7   7   7   8   8   9   9  10  10  10  11  11  12    
     16   4   4   4   4   4   4   4   4   4   4   5   6   5   6   6   7   7   7   8   8   9   9  10  10  10  11
If you have an effective skill of 13 and the defender has a defense of 8 you look up 13 across the top column, follow it down to the 8 row, and find the target number is 11. If attacking a player needs to roll an 11 or less, if defending a player needs a [20-11]=9 or less.

Simply treat a critical failure by a defending player as a critical success by his attacker. This will skew the critical success and failure results a bit, but overall result in approximately the same chances of success in combat.
Thank you for this awesome table. I was looking for this exact solution in my own campaigns but I plan to use it only with mooks.
I have a question regarding your table, did you consider that skills above 16 crit on 6? I think you did, if so, why in the 17 column the lowest number for attack success is 5?
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Old 07-29-2021, 10:24 AM   #33
Plane
 
Join Date: Aug 2018
Default Re: combat without actual defense rolls?

Ultra-Lite just has you subtract half your opponent's DX+skill from yours to determine hits. Or full if they chose "Duck!" (Ultra-Lite's equivalent of All-Out Defense)

My guess is it's sort of similar to this chart except it can fully remove the ability to defend unlike full rules where you can always get that crit defense.

Also Ultra-Lite lacks crit successes too. Neat thing about that is the combat skills like Swashbuckler/Knight also basically come with assumed armor/DR too.
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Old 07-30-2021, 03:33 AM   #34
whswhs
 
Join Date: Jun 2005
Location: Lawrence, KS
Default Re: combat without actual defense rolls?

Quote:
Originally Posted by Plane View Post
Neat thing about that is the combat skills like Swashbuckler/Knight also basically come with assumed armor/DR too.
That almost sounds like D&D, with its assumption that higher level characters have more hit points.
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Old 07-31-2021, 09:19 AM   #35
Emerikol
 
Join Date: May 2021
Location: Eastern Kentucky
Default Re: combat without actual defense rolls?

Attacker Defenders Skill
Skill 5 6 7 8 9 10 11 12 13 14 15 16
5 4.50% 4.37% 4.18% 3.91% 3.59% 3.24% 2.89% 2.57% 2.30% 2.11% 1.98% 1.90%
6 8.92% 8.57% 8.06% 7.34% 6.48% 5.56% 4.63% 3.77% 3.05% 2.54% 2.19% 1.99%
7 15.54% 14.87% 13.88% 12.48% 10.82% 9.03% 7.23% 5.57% 4.18% 3.18% 2.52% 2.12%
8 24.81% 23.70% 22.03% 19.68% 16.90% 13.89% 10.88% 8.09% 5.75% 4.08% 2.97% 2.30%
9 35.85% 34.20% 31.72% 28.26% 24.13% 19.68% 15.22% 11.09% 7.63% 5.15% 3.50% 2.51%
10 47.77% 45.54% 42.20% 37.52% 31.94% 25.93% 19.91% 14.33% 9.65% 6.31% 4.08% 2.74%
11 59.69% 56.88% 52.67% 46.78% 39.76% 32.18% 24.59% 17.58% 11.68% 7.47% 4.66% 2.97%
12 70.73% 67.39% 62.37% 55.35% 46.99% 37.96% 28.94% 20.58% 13.55% 8.54% 5.20% 3.19%
13 80.00% 76.21% 70.52% 62.55% 53.07% 42.82% 32.58% 23.10% 15.13% 9.44% 5.65% 3.37%
14 86.63% 82.51% 76.34% 67.70% 57.41% 46.30% 35.19% 24.90% 16.26% 10.08% 5.97% 3.50%
15 91.04% 86.71% 80.22% 71.12% 60.30% 48.61% 36.92% 26.10% 17.01% 10.51% 6.18% 3.58%
16 93.69% 89.23% 82.54% 73.18% 62.04% 50.00% 37.96% 26.82% 17.46% 10.77% 6.31% 3.64%

Chance is percent chance the attacker will hit.
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Old 07-31-2021, 09:28 AM   #36
Emerikol
 
Join Date: May 2021
Location: Eastern Kentucky
Default Re: combat without actual defense rolls?

Here is a better picture
urlToPic
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Old 07-31-2021, 11:59 AM   #37
Plane
 
Join Date: Aug 2018
Default Re: combat without actual defense rolls?

One major change would be that you would need to declare the defense before the attacker actually rolls which eliminates the whole "I can wait to see if it misses before committing" that GURPS usually has
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Old 08-01-2021, 07:45 PM   #38
Infornific
 
Join Date: Dec 2004
Default Re: combat without actual defense rolls?

Quote:
Originally Posted by Plane View Post
Ultra-Lite just has you subtract half your opponent's DX+skill from yours to determine hits. Or full if they chose "Duck!" (Ultra-Lite's equivalent of All-Out Defense)

My guess is it's sort of similar to this chart except it can fully remove the ability to defend unlike full rules where you can always get that crit defense.
The weakness with ultra-lite is attack probability rises faster than defense probability as skill rises. Kind of the opposite of 3E where high skill favored defense.

One simple method for a single attack roll combining offense & defense:

Attack Roll = 10+((Attack Skill - Defense Skill)/2)

So someone with skill 14 attacking someone with a skill 12 would need 11 or less to hit. The other way around would require a 9-.

To translate Dodge rolls into a defensive skill, double it and subtract 6.

That might be more arithmetic than desirable. Alternately, calculate attack value by dividing Attack skill by 2. Defense Value would just be Dodge, parry or block. So the attack roll would be:

13+(Attack Value-Defense Value)

Range & hit location modifiers should be halved (rounding up.)

The drawback is that it would result in even numbered skills being favored.
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Old 08-02-2021, 10:53 AM   #39
Varyon
 
Join Date: Jun 2013
Default Re: combat without actual defense rolls?

Quote:
Originally Posted by Infornific View Post
The drawback is that it would result in even numbered skills being favored.
That's already the case, albeit to a reduced extent (currently, even-numbered skill levels are where Parry gets a boost). An option to avoid this would be to retain fractions, keeping in mind you still roll under, so if the final skill level is 12.5, that's functionally indistinguishable from skill 12. The important thing is how you get there. In this case, odd numbers will be slightly favored, but not quite to the extent even numbers are currently. Consider the cases of skill 12 vs 12, 12 vs 13, 13 vs 12, and 13 vs 13.

12v12: Under the current system, this is Attack 12 vs Parry 9. Under your proposal, this is Attack 6 vs Parry 9, or 10 to connect.

12v13: Under the current system, this is Attack 12 vs Parry 9, same as above. Under your proposal, with my modification, this is Attack 6 vs Parry 9.5, or 9.5 (9) to connect.

13v12: Current system, 13 vs 9. Proposal, 6.5 vs 9, or 10.5 (10) to connect.

13v13: Current system, 13 vs 9. Proposal, 6.5 vs 9.5, or 10 to connect.

As you can see, under the current system, going from 12 to 13 gives an increased hit chance but no increased defense, favoring even-numbered skills. With your proposal with my modification, going from 12 to 13 has no effect on hit probability if your target has an even-numbered skill, but increases it if they have an odd-numbered skill; conversely, going from 12 to 13 reduces the enemy's hit probability if he/she has an even numbered skill and has no effect on hit probability if he/she has an odd-numbered skill.
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