Converting to and from Bushido and d20

Is it possible to convert Bushido character to and from d20?

As I see it there are several posibilities that might make this useful:

1. use the d20 creatures with Bushido
2. use the Bushido creatures with d20
3. use the Bushido RPG with a d20 resultion system
4. use the Bushido resultion system with d20 RPG

Terms

Abilities

d20, the intrinsitic constant traits of a character, valued from 3 to 18 for a normal human. What Bushido calls Attributes.

Attribute

Bushido, the intrinsitic constant traits of a character, valued from 1 to 40 for a normal human. What d20 called Abilities.

BCS

Bushido, Base Chance of Success, Skill Score divided by 5 or Attrubute Score divided by 3.

MCS

Bushido, Modified Chance of Success, BCS plus character specific modifers like Level Bonus and Weapon or Tool Bonuses.

Basic Resultions Systems

How it works

The systems are basically closer than they seam as you can convert from a target system to a roll under system with the follow equations

The basic Bushido system is:

Skill_BCS := ( Attr_Value + Skill_Value ) / 5

Skill_MCS := Skill_BCS + Proffesional_Bonus + Other_Bonuses

Skill_MCS + Situation_Modifiers >= (Low)d20

and d20 is

Skill_Mod := Attr_Value + Skill_Value + Char_Modifiers

Skill_Modifier + (High)d20 => Target DC + Situation_Modifiers

To convert you need to know that when you inverse the probabilities from a high d20 to a low d20 you do it by subtracting from 20 ie

(High)d20 == 20 - (Low)d20

20 - (High)d20 == (Low)d20

So that the Bushido resolution system can be rewritten

Skill_MCS + Situation_Modifiers >= (Low)d20

Skill_MCS + Situation_Modifiers >= 20 - (High)d20

Skill_MCS + (High)d20 >= 20 - Situation_Modifiers

A 1st level Bushi will have a MCS in combat about 15 and a 1st level d20 Fighter will have a To Hit of (Str +3, Attack +1, Weapon Prof. +1) = +5 (ie 10 difference).

If you extend this, 6th level Bushi will have a MCS of about 26 and 3 attacks per round. An 11th level Fighter will have a Attack of +16 and 3 attacks around. (again 10 difference). Hence I am lead to the follow very crude conclusions.

1. you can convert from a Bushido MCS to d20 skill value by subtracting 10, and via a versa by adding 10.
2. a d20 characters level is equal to about double a Bushido characters.

• Yes this is not right, a 11th level Fighter would have +16, +11, +6 but he would also most likely have a whole set of magic items or other feats that would attually improve its odds. So for the moment this is an educated guess it might be nessary to do some statistical computations to get the value correct.

Using the d20 System

The basic roll system becomes:

( Skill_MCS - 10 ) + (High)d20 >= 10 - Situation_Modifiers

Situation Modifiers are themselves sensity to the side of the equation they are on, so if you invert the Bushido ones then they are the same way round as the d20 system.

Armour Class are close to the same ranges even if they are based on a slightly different system. By following the same logic you end up with adding 10 to the AC. Which is the same as d20 anyway.

( Skill_MCS - 10 ) + (High)d20 >= 10 + Bushido_AC

Remeber that the -10 would be predone by the player on there character sheet. And the 10 modifier is in fact the default target in the d20 system and all the TN assume it.

For Example, assume a character has a Climb MCS of 18 that means in the d20 system they have a Skill Value of +8. If they have to make a standard TN climb of 15 that means they roll d20+8 to beat or equal 15 in the standard way.

Using the Bushido System

The basic roll system becomes:

( Skill_Modifier + 10 ) + Situation_Modifiers >= (Low)d20

and attack

d20_AC := d20_AC_Mods + 10

( Skill_Modifier + 10 ) - ( d20_AC - 10 ) >= (Low)d20

( Skill_Modifier + 10 ) - d20_AC_Mods >= (Low)d20

Remeber that the +10 would be predone by the player on there character sheet.

For example, assume a character had a Climb of +6, that means there Climb MCS would be 16. If they climb was a -5 difficulty they would need to roll under 11 to succeed.

The Attribute / Abilities System

Both systems use a different scale but the weakest 'Human' in d20 is 3 and strongest is 18 on a bell shaped curve (approximatly). Bushido uses a linear range from 1 to 40 but because it uses a fixed point system it produces the same result for orinary people.

If we multiply the d20 values by 2 we get to the Bushido range. IE d20 Strength 16 become Bushido Strength 32 or BCS 10 this make the transformation simple.

Bushido_Attribute_BCS := Bushido_Attribute_Score / 3

d20 Ability Mod := ( d20_Ability_Score - 10 ) / 2

Bushido_Attribute_Score := d20_Ability_Score x 2:

d20_Ability_Score := Bushido_Attribute_Score / 2

From d20 to Bushido

Hence the Creature:

d20 Ability Values: Str 19, Dex 15, Con 10, Int -, Wis 10, Cha 2

becomes

Bushido Attribute Score: Str 39, Dex 30, Con 20, Int 0, Wis 20, Cha 4

But the attributes are different as well:

• Strength is simple, Str = Str.
• Bushido Health becomes Con.
• In d20 Wis is the intuit attribute not Int but Int it is also used for knowledges so lets say Wit = (Wis+Int)/2.
• In Bushido Will is Wis and Cha so lets do the same average them Wil = (Wiz+Cha)/2
• Bushido Defness is closed to d20 Dex and is used in both system for initiative order.
• Speed is a problem as in d20 your move is a function of your creature type, weight and your number of attacks is a function of your class and level. Lets use a Bushido system for this rather than a d20 one, hence we will use the creatures move alone. BAP = Speed / 3 ft/rnd. Move = ft/rnd. The average Bushido Human BAP is 3 (guess) in d20 this would be 30 (I think). Move = 30 ft = 10xBAP = 10x (Speed/3) Hence Speed = Move * 3 / 10. If we simplify it and say divide by three.

Bushido_Str = d20_Str * 2

Bushido_Dft = d20_Dex * 2

Bushido_Spd = d20_Move/3

Bushido_Hlh = d20_Con * 2

Bushido_Wit = d20_Wis + d20_Int

Bushido_Wil = d20_Wis + d20_Cha

Hence:

d20: Str 19, Dex 15, Con 10, Int -, Wis 10, Cha 2, Move 40ft

become

Bushido: Str 39/13, Dft 30/10, Spd 13/4, Hlh 20/6, Wit 10/3, Will 12/4

BAP 15, MNA 1, ZAN (55)

From Bushido to d20

(Not written yet)

Damage System

(Not written yet)

Experience System

(Not written yet)

Monsters

The systems are not comparable but if you wanted to you can crudly transform from one to another with the conversions from above.

From d20 to Bushido

Lets asume we had a creature like this.

 -8<-

(name removed but it is not a WotC monster)

 Huge Vermin

 Hit Dice: 9d8 (40 hp)
 Initiative: +2 (Dex)
 Speed: 40 ft
 AC: 17 (-2 size, +2 Dex, +7 natural)
 Attacks: Bite +8 melee, tail +3 melee, 1d3 spines +3 melee
 Damage: Bite 2d6+4 and poison, tail 2d6+2 and poison, spines 1d8+2
 Face/Reach?: 10 ft by 30 ft/10 ft
 Special Attacks: Poison, spines
 Special Qualities: Vermin
 Saves: Fort +6, Ref +5, Will +3
 Abilities: Str 19, Dex 15, Con 10, Int , Wis 10, Cha 2
  Skills: Climb +12, Hide +1, Spot +7

 Climate/Terrain?: Any temperate and warm land and underground
 Organization: Solitary
 Challenge Rating: 4
 Treasure: None
 Alignment: Always neutral
 8<

As a first pass I could convert it to: (The base damage die are similair so we only need to figure out the strength mods)

Str 39/13, Dft 30/10, Spd 13/4, Hlh 20/6, Wit 10/3, Will 12/4

BAP 15, MNA 1, ZAN 1 (55), AC 7

Attacks

BCS Dam

1x Bite 18 2d6+str+poison

1x Tail 13 2d6+str+poison

1d3 Spines 13 1d6+str

Skills

BCS

Climb 22

Hide 11

Spot 17

Only Budo left, you have most of the creature converted.

From Bushido to d20

(Not written yet)

The Task System

I have been stuck on this because the Task system in Bushido is a fundimental part of the system but in d20 it a random hotch poch of ill tought out rules.

Bushido

In Bushido it is simple, the amount you make your role is called the Effect Number.

    EF = Min(1, MCS - (Low)d20)

If roll is crit add 2d6 (IIRC)

Personally I have never like this so I have been experinmenting with removing the subtraction.

    EF = (high)d20 iff roll <= MCS

if roll == MCS then crit, 20 always fail etc This has the advantage that on a success you never get a zero and have to worry about the min of 1.

When the total of the EF is greater than the Task Value the Task is done in that meant Task Turns.

d20

d20 system does not have a system per say, there is one on constructing items, you can also retry some skill until you make it, then there is the take 10 and 20 system.

The crafting objects skills work by having a DC which you have to beat normally 15 or 20. If the Roll * DC is greater or equal to the cost * 10 then the item is made. If it is not made then that is how much you have made of the time that week. If you fail by more than 5 the item is destroyed.

Check where there is no adverse effect you can just retry until you make it or use the take 10 or 20 system. This just assume that you take longer.

and is not a task system as such as there is no commutative value to record the progress of the task. It is either done it or not. So I suggest that we ignore this part of the the d20 system.