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determining dodge

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#1 Oct 28, 2009, 12:05 pm

blueice
Fledgling

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Posts17
JoinedOct 21, 2006

hello i have hit a wall in trying to rewrite the check_dodge function in my game. i scoured google, but the only thing i could find, besides references to world of warcraft, were function and formulas based entirely on the individual and not both fighters. just barely got back into programming so its probably something really simple, but god help me i cant figure it out.

Code:

bool check_dodge( CHAR_DATA *ch, CHAR_DATA *victim )
{
    int perc = number_percent();
    double dif, attacker, vict;

    attacker = (sqrt(get_curr_spd(ch))*1.25) + (sqrt(get_curr_agi(ch))*.75);
    vict = (sqrt(get_curr_spd(victim))*1.25) + (sqrt(get_curr_agi(victim))*.75);

    if ( attacker == vict )
        dif = number_range(5,10);
    else
        dif = (attacker - vict)*10;

    if ( dif > 0 )
    {
        if ( dif >= perc )
            return FALSE;
    }
    else
    {
        dif = dif * -1;
        if ( dif <= perc )
            return FALSE;
    }

    if ( !IS_NPC(victim) )
        act( AT_SKILL, "You twist your body to the side and dodge $n's attack.", ch, NULL, victim, TO_VICT );

    if ( !IS_NPC(ch) )
        act( AT_SKILL, "$N twists $S body to the side and dodges your attack.", ch, NULL, victim, TO_CHAR );

    act( AT_SKILL, "$N twists $S body to the side and dodges $n's attack.", ch, NULL, victim, TO_NOTVICT );
    return TRUE;
}

the idea is that as the difference increases, the harder it will be for the victim to dodge your attack, and as the difference decreases, the harder it will be for you to him. any ideas?

#2 Oct 28, 2009, 12:21 pm

Kayle
Nibelungen

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JoinedMar 21, 2006 WWW

What exactly are you trying to do? I'm not sure I really follow what it is you're attempting enough to offer advice yet.

.........................
Owner/Coder Coder
Malevolent Whispers Star Wars: The Sith Wars
{Development Phase - Not accepting players} {Open Alpha - Players welcome, but with frequent changes to core systems.}
IMC2 Contact: Kayle@MW IMC2 Contact: Kayle@SWTSW

#3 Oct 28, 2009, 1:38 pm Last edited Oct 28, 2009, 1:39 pm by blueice

blueice
Fledgling

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Posts17
JoinedOct 21, 2006

i want to change the check_dodge function calculate the chance to dodge based on both the attacker and the victim, by comparing their combined attributes that affect the chance to hit/dodge, speed and agility.

difference = attacker chance to hit - victim chance to dodge
-100 0 100
completely miss |--------------------------()---------------------------------| unable to miss

#4 Oct 28, 2009, 2:12 pm

David Haley
Sorcerer

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Posts830
JoinedJan 29, 2007 WWW

What is the problem that you're seeing with your code? I haven't gone through it beyond a cursory glance, but it looks like the general idea is what you've described. Is it behaving differently from your expectation? .........................
David Haley
Head Coder, Legends of the Darkstone
BabbleMUD Project
http://david.the-haleys.org

#5 Oct 28, 2009, 3:48 pm

blueice
Fledgling

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Posts17
JoinedOct 21, 2006

it seems that no matter what i do, i have problems with fights where either a NPC that shouldnt be able to dodge a single attack does, or fights where the fighters are extremely close and almost every attack is being dodged by both parties. like u said it seems like it should work, but doesnt. strength and agility have no restrictions on my game, so the two attributes can range anywhere from 1 to 10000 and above, though the average combination for my highest experienced players is around 3000

#6 Oct 28, 2009, 6:46 pm

blueice
Fledgling

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Posts17
JoinedOct 21, 2006

the problem has to be in my execution of this part

Code:

    if ( dif > 0 )
    {
        if ( dif >= perc )
            return FALSE;
    }
    else
    {
        perc = perc * -1;

        if ( dif <= perc )
            return FALSE;
    }

no matter how i can change the evaluations for diference and percentage, one end of the spectrum messes up, it seems to be the middle area where it is messing up, perhaps i should only be evaluating it based on whoever has the highest total value?

#7 Oct 28, 2009, 6:59 pm

blueice
Fledgling

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Posts17
JoinedOct 21, 2006

ok so maybe i can figure this out if i focus on one thing at a time. ok based on a situation where attacker value is always greater than vict

Code:

    if ( dif > 0 )
    {
        if ( perc < dif )
            return FALSE;
    }

ok so if i try it this way, it works perfectly for someone who is extremely higher than the other person, but as the difference between them gets closer, the chance to dodge increases so much that the attacker actually can barely hit the vict, if i switch the evaluator around ( perc > dif ), its the exact opposite, the closer the speeds the more dodges happen. how can we get this better?

#8 Oct 29, 2009, 1:31 pm

David Haley
Sorcerer

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Posts830
JoinedJan 29, 2007 WWW

One problem here is that you are comparing a number that is basically unbounded with a number generated as a percentage. If the difference between them is, say, 100, then perc will always be less than diff.

If you want to compare against a percentage, you need to find some way of normalizing the difference between their "dodge scores" to be comparable to the percentage roll. This isn't really a programming problem, it's a design problem. You have to make sure that you're coming up with a difference that makes sense to compare. Your differences are on an entirely different scale than your die roll.

You should work out a few cases by hand where you write out the speed and agility of each, then run those through your formula to get their "dodge scores", compute the difference, and then see what the numbers are like as you scale input variables. This will give you a feeling for how to normalize the difference against the percentage. You can do this by graphing the difference along the x axis, and the normalized number on the y axis. Make sure to always express things the same way, e.g., always trying to figure out if the attacker succeeds, or always trying to figure out if the defender succeeds. This will help you get your signs right.

Basically, you need to work this out by hand and see what the numbers actually are, and not try to write formulas until you understand how the numbers and signs interact. .........................
David Haley
Head Coder, Legends of the Darkstone
BabbleMUD Project
http://david.the-haleys.org

#9 Oct 31, 2009, 1:49 pm

blueice
Fledgling

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Posts17
JoinedOct 21, 2006

thanks for the suggestions, i think this new version is working pretty well, time will tell.

Code:

bool check_dodge( CHAR_DATA *ch, CHAR_DATA *victim )
{
    double perc = ((double)number_range(50,200)/100);
    double dif, attacker, vict;

    if ( !IS_AWAKE(victim) )
        return FALSE;

    attacker = (sqrt(get_curr_spd(ch))*1.25) + (sqrt(get_curr_agi(ch))*.75);
    vict = (sqrt(get_curr_spd(victim))*1.25) + (sqrt(get_curr_agi(victim))*.75);

    if ( attacker == vict )
    {
        // with fighters or equal caliber, lets give it a generic 10% chance to dodge
        if ( number_percent() > 10 )
            return FALSE;
    }
    else if ( attacker > vict )
    {
        dif = vict*perc;

        if ( attacker > dif )
            return FALSE;
    }
    else
    {
        dif = attacker*perc;

        if ( vict < dif )
            return FALSE;
    }

    if ( !IS_NPC(victim) )
        act( AT_SKILL, "You twist your body to the side and dodge $n's attack.", ch, NULL, victim, TO_VICT );

    if ( !IS_NPC(ch) )
        act( AT_SKILL, "$N twists $S body to the side and dodges your attack.", ch, NULL, victim, TO_CHAR );

    act( AT_SKILL, "$N twists $S body to the side and dodges $n's attack.", ch, NULL, victim, TO_NOTVICT );
    return TRUE;
}