Magician.md

Magic Damage Formula - v40 Reverse Engineering

Overview

This document contains the 100% IDA-verified magic damage formula for MapleStory v40, reverse engineered from sub_515307 (CalcMagicDamagePerHit).

---

Formula

BaseDamage = (INT × 0.5 + (Magic × 0.058)² + MagicInterp × 3.3) × EffectiveSkillMAD × 0.01
FinalDamage = Floor(BaseDamage) - DefenseSub

Variables

Variable	Description	Source
INT	Character's INT stat	GetSecureValue(a4+15)
Magic	INT + MATK (total magic power)	GetSecureValue(a5+96) + GetSecureValue(a5+108)
MagicInterp	Interpolated magic (min to max via RNG)	See Mastery Interpolation
EffectiveSkillMAD	SkillMAD × AmpMultiplier	Amp is integrated into skill damage
DefenseSub	Monster defense reduction	Interpolated MDD × [0.5, 0.6]

---

IDA Constants

Address	Name	Value	Usage
0x6295C8	dbl_6295C8	0.5	INT coefficient
0x62BD30	dbl_62BD30	0.058	Magic quadratic coefficient
0x62BD28	dbl_62BD28	3.3	Magic linear coefficient
0x62B6D0	dbl_62B6D0	0.01	Skill scale factor
0x62BD08	dbl_62BD08	5.0	Mastery calculation
0x62BD18	dbl_62BD18	10.0	Mastery base value
0x62BD00	dbl_62BD00	0.009	Mastery scale
0x62BC80	dbl_62BC80	99999.0	Damage cap
0x62BCE8	dbl_62BCE8	1e-7	RNG normalization

---

Mastery Interpolation

The mastery factor determines the minimum damage range:

// IDA Line 103
v52 = (skillMastery × 5.0 + 10.0) × 0.009

Skill Mastery	v52 Result	Min Damage %
0	0.09	9%
10	0.54	54%
20	0.99	99%

Interpolation Logic (Lines 220-238)

v35 = Magic;           // Start at max
v59 = Magic × v52;     // Calculate min

if (v59 < v35) {
    Swap(v35, v59);    // v35=min, v59=max
}

v35 = v35 + (v59 - v35) × rngFactor;  // Interpolate

---

Multi-Hit RNG Pattern (Critical)

CalcMagicDamagePerHit pre-generates 7 random values ONCE at the start, then cycles through them for all hits:

// Lines 76-84: Pre-generate 7 randoms
uint v51[7];
v62 = 0;
do {
    v51[v62++] = CRand32::Random();
} while (v62 < 7);

// In the hit loop (for each hit):
accRandom = v51[v62 % 7]; v62++;   // Accuracy
dmgRandom = v51[v62 % 7]; v62++;   // Damage
defRandom = v51[v62 % 7]; v62++;   // Defense

Multi-Hit Example (Magic Claw - 2 hits)

Hit	Acc Index	Dmg Index	Def Index
1	0	1	2
2	3	4	5

---

Elemental Amplification

Amp is integrated INTO the skill damage, not applied after defense:

EffectiveSkillMAD = SkillMAD × (AmpY / 100)
// Example: 55 × 1.35 = 74.25

Important: The amp multiplier uses the skill's y property (e.g., y=135 → 1.35×)

---

Complete Implementation

// IDA Constants
const double INT_COEFF = 0.5;           // dbl_6295C8
const double MAGIC_QUAD_COEFF = 0.058;  // dbl_62BD30
const double MAGIC_LINEAR_COEFF = 3.3;  // dbl_62BD28
const double SKILL_SCALE = 0.01;        // dbl_62B6D0
const double MASTERY_MULT = 5.0;        // dbl_62BD08
const double MASTERY_ADD = 10.0;        // dbl_62BD18
const double MASTERY_SCALE = 0.009;     // dbl_62BD00

public int CalculateMagicDamage(
    int intStat, int matk, int skillMastery, int skillMad, 
    double ampMultiplier, double dmgRngFactor)
{
    int totalMagic = intStat + matk;
    
    // Step 1: Calculate mastery factor (IDA line 103)
    double v52 = (skillMastery * MASTERY_MULT + MASTERY_ADD) * MASTERY_SCALE;
    
    // Step 2: Interpolate Magic stat (IDA lines 220-238)
    double v35 = totalMagic;
    double v59 = v35 * v52;
    
    if (v59 < v35) {
        (v35, v59) = (v59, v35);  // Swap for min/max
    }
    
    v35 = v35 + (v59 - v35) * dmgRngFactor;  // Interpolate
    
    // Step 3: Apply formula (IDA lines 240-242)
    // Amp is integrated into skillMad
    double effectiveSkillMad = skillMad * ampMultiplier;
    
    double intTerm = intStat * INT_COEFF;
    double quadTerm = Math.Pow(totalMagic * MAGIC_QUAD_COEFF, 2);
    double linearTerm = v35 * MAGIC_LINEAR_COEFF;
    
    double damage = (intTerm + quadTerm + linearTerm) * effectiveSkillMad * SKILL_SCALE;
    
    return (int)Math.Floor(damage);
}

---

Key Discoveries

Finding	Description
v64 = INT	Initially assumed to be LUK, but GetSecureValue(a4+15) returns INT
Skill Mastery	Read from skill data offset 268, not a fixed 60%
Amp Integration	Applied inside formula, NOT after defense subtraction
7 Random Cycle	All hits share the same 7 pre-generated randoms, cycled with modulo 7
Mastery Formula	(mastery × 5 + 10) × 0.009 converts skill mastery to interpolation factor