ace/Source/ACE.Server/WorldObjects/SkillCheck.cs

using System;

namespace ACE.Server.WorldObjects
{
    public static class SkillCheck
    {
        public static double GetSkillChance(int skill, int difficulty, float factor = 0.03f)
        {
            var chance = 1.0 - (1.0 / (1.0 + Math.Exp(factor * (skill - difficulty))));

            return Math.Min(1.0, Math.Max(0.0, chance));
        }

        public static double GetSkillChance(uint skill, uint difficulty, float factor = 0.03f)
        {
            return GetSkillChance((int)skill, (int)difficulty, factor);
        }

        public static double GetMagicSkillChance(int skill, int difficulty)
        {
            return GetSkillChance(skill, difficulty, 0.07f);
        }
    }
}