Damage conversion for Skills with Gain +X% as Extra

[laFleuere2]

Check version

• I'm running the latest version of Path of Building and I've verified this by checking the changelog

Check for duplicates

• I've checked for duplicate open and closed issues by using the search function of the issue tracker

Check for support

• I've checked that the calculation is supposed to be supported. If it isn't please open a feature request instead (Red text is a feature request).

What platform are you running Path of Building on?

Windows

What is the value from the calculation in-game?

In-game testing:

• Eye of Winter (Gain +100% Damage As Damage of Corresponding Ground Effect)
• Wake of Destruction (Drop Shocked Ground while moving)
• Call of Brotherhood (Convert 100% of Lightning to Cold)

With this setup we never shock enemy with our Eye of Winter passing through Shocked Ground. Which means Gain +X% is happening on step 1 of conversion (Skill conversion) and later on step 2 (all other conversions) we're converting Gain +X% (from Skill) into Cold Damage (through Call of the Brotherhood).

Source: https://www.poe2wiki.net/wiki/Damage_conversion#Skill_vs_other_conversion

What is the value from the calculation in Path of Building?

PoB does not support Eye of Winter Gain +X% As Extra, so I've checked it with Twister (checked "Twister gained Lightning Element") and modified Wake of Destruction (removed added flat lightning damage). And in Calculation - we still see Lightning Damage instead of Cold damage.

How to reproduce the issue

Equip:

• Twister;
• Call of the Brotherhood;
• Wake of Destruction (remove added flat lightning damage for clarity);

In configuration:

• Check "Twister gained Lightning Element" (as passing through Shocked Ground);

In Calculation:

• Twister still have Lightning Damage.

PoB for PoE2 build code

eNqtG21v4jjz8_IrLKST9nRXCqGUFrV3oqVvUl84aHef59PJTQzkqYm52GnLnu6_PzO28wIlNG5vV9pNnJnxeGY8bzZHv7_OOXlmsQxFdFxvNZp1wiJfBGE0Pa4_3J_vHNR__612NKRqdjc5SUKOX7zfal-O9AtRNJ4y9S0l0PyzVSc-p1Le0jk7ro9oNGVxnVDpsyg4zT_ciogB5IzG1FcsvmbPjPcTJW5EAF9VnMBXjoPAVJ08h-zFfLm6Gd6N7utkTsNoLPwnpi5ikSwQCpj6cjTkdMnisaKKSPjnuN6HxdEpG9A5_AuUKE-AzH6j2_W67b12t1Pf3Yp4ksRSuWOPF4wFGUKr4R2UQQ5jdjaZMF-Fz-w0DtXpjEZ-Ple3DG8DbKtRzhCC3yRchQseokYsilcGf_mGuldK-14oygfDcQZ60NjfP2xtBxcqA2-WQX4P1eyEgySrE0eUq2kUKuaGMxShFJH7IooYpes4TTiHfVMJdsQki5-pCle5Kact5o9h5CKifszo3cQY3YgGYSJvmIqZzOdqlKr6hkb0VMhcd3vbIIcshn2vVhCa7yCMmS_AVRRROo2WV2Gazcil812HE1Yd0mkpFsGVm4-t42xcFc6Z8McYGoGvrAY5FgmvCKni913iiP1VhOuUUhuw19xpdraQWwH0Sie-ivIleN4WekXAwy3sPQvc_--L5T4OHxPFKgCiuzq7HObCOWy0DtqtLgSxprdfyvNwtpShT_kNfQ3nyRyiwj19Yjlnh3vlBj2dqQi8Xhlqt9RBnYcxK8PqHJY7Qh58AGtGhSxlsVvudsLokkZB3_cTSGGWVbRK46eISVk1BIBLr4yB3iNPT7ZlJX4PYa8iP5fNNqIPUWyZqUAeEUbgKDBzeuSsIkY-hXU3-Y5rNrdPNWWRnW9ZTUbXjPmzC9DdiFbZNRhc8qDqbRUrwhbFupXoBrEeeNUQHISEiJuFtNdob0NyFNN4EUJ2WYUjA7lh9Q44DgI4i1g8XY5nIeP5VN5eFfBUZKd0UQFTW0ARvZIlrM7nZMxFVEdtYXh2ne2ZymI86m6Xg4GuJoJnGrC1QqPcnhnUAk4Yw1j8D0sr7oYGy-DcHeODsw3YhCOaQAVCwKyMUXWCfjwXSSEv2q4-A11Je2l2YOrjEQsSfyVvKY3wWcV7wqGIr7qODEtL2wm1rxT1nwYimLqp1Aljlb9xsliAz8KtUJUAJj4Q_MNCRrzTqQB9B9u46Kia23Kk6hPk0JUnyLK-9Vm8TkWU6mvBzG1tmirAlSfI1HkDbnIOIUc3dW5Esa9TauErON9n4BMeJKxx_BRyXii02-0tfSHJwGo2Vuilgeg84bxS20ADVmxfDMULiGyGrT7pBg2JdYZQutLzmEU_lpXpr4BXmuAsCiBJB1lWnmMdY9M0J8lkIokv5o9UXYNdHdfr5BHG0mcoDCSzLwbjPpxDBJNyQBUlgS3yvtE4pJFq6Ubn2qCnByWjsT9LyeZv55TzR_Bqlv7Rrm7J4tPVfCFiRdgr_jeksVoe1yeUS2YAb4ViEjlCpPTl6EqxuSSJZKbW_87oQkRjBpNGIZgs1VsBgfQY8jUTLyizQQgbJUZblbZ1q1eLoCQMTAPXrAf7jfjtywje1bJHHm6v_ng4q32HqouICRkwCfg6hpCvt4L0g4AFJHMQxMSZn2vAYRLjFzadwrismZjVI51uzWRGxKRGPeLt1awwewS2FGk2YNPmQ6dJDJwroIgBFUhmX7zaHwnlmkuvWdMNaijge6S1XwPx8tAPleyRZu1vu7ae90-r-RMJIz9mVAKl1AMQ7QJqf8fYC-81G51_vrabO_vNn4vAZgEEKkqysoDaIBYLeMZWd0Cw1w0QL-hOyFw8w9p_JZxKzBrIAZgGKk6igI_ATenmO9HTmp6e1YY2xi0QaSGyixpcVeVm9Z2CIaL61IyRk1jAf_FMiKB2Lxb0BxkBcwX5tb2i_Fq1vxWdyh5PdfxPQU6_fPWaO20UlBIFKzBuHHenRaZKmT7IKnKrueM1f0bcq0hBQA6nLMeZQ5lTBP_qdXbanRWdYCVEdKYM9ay2SUywVxSZ8pcjgXdiP0AMuBWTRQ2Kk59QNOs2TE5FBHEILQ74w0BrP_xLytsC0X4XYu9diE65ibRXTWTUH53VbtkLQYBa_0ksaYQ7gsa105hOQAA9gj6jBptzEr72CJ4MbXkZg4et8FLcu-acCIxtjH9royRiFmrzY26r3YNVW70AOShJdBDvmVWQ-1ksXippbU1a4EbLva1BM1oYc6FICBjDx4fRNcaASJ-hGRzSIuMXTGcQ4irIglo53gnjygHcTuO5TgPOmbQc4MEFEs8BHkPznLQdZ3Dh6Bxc69MHMDx36RYmab-7jHnCmYsGLxmfOyGciGBJ0qrRAUsomcO3qimw5axyz9EIXeAxWBVZ8iohOM_gYrUXHBIJ-YEN-wbFOCBwMjpb1PkePt1DyLLpHTYAsrN0fCFzyC5YvDS1kNR5LZ7iY0SNI8qNjOyYnsme9UN4XhaBgDkRYILYae51Dus2V6Hxsp9fDUA47f2g1mGFOwV7KxcIzDRGBLBu_fBlptRC9nZ3X15eGguqZmLCXiFJakB6vrsAJFjbjkS3vYO0d_vw52Ta1380od2U0pGNFlbGWCzGYWDSZXjvp6lG-gFCv7o1K8P0_TV7hkw2fba0dleIHe2ifLUmUAH4AHmUb75dRYtEWXXOQ-n_iYUF3oDQdPXljLPz87PT-6tvZ1a3RRS90j-jZP6IR_3m_zwMjU2zCUoXzukCkpa0OCAyeZTm43H9W8hedKAbMEVDLk1M0iMmWXaipvEuw-wmBdLKX10onb1C2gQS-A5lUBwyy1f25syUYQEboVieGWp4OcGFkOkuncJWMS1YLSl9A8SFCl7RsMvBRydcSFMotzPbZ2dJqOWCSbDJcBL6WNcVVX4P38yYk1yy0zGrb9sIc6Gh738YAubRBdnc6jDY9tlJqvoiiZWqeXZBHzCf2rWbRxfkrKsvoks8XEEq2ZgTJUhqtZHDpumHHEtSq9kzzrIBF4J3WOHZiGAo3YCPSgccN45xp5ZO4d1JVvr4U0sIn1xQzRGfXgM-OW0ae-xldnvoumVXD6e0PoojLqRMRWxlaFuiTmpIU70ge3ZaSXo8pBdhX5w2ivbB_WcRBqZRrrfM2qCb04Ao_nkyuvv_L5DJDng-T0tXGFbT9rkU3VyjLGI_qBDL4s8RwT32OQq41T5HQVcCH8YeZTnIaGv6sXneaeqt0hcH_Kyx_GEKpv39YXTdna-IXeb6wZ51tzf3_dmIk_9USTRITGvNhdTbRWmu1tzH52iZsPgvLdTsd3u1KHcAZsCZEITxyyxR_Cil7GzrklGOt18F_xzBN1eoKhPbsD2hNkwWNApSaner2flHpSeUBKK6NTvAtq78FJcQrefLbXSOdtOC7kifwUB5iJ16amMungOOZ-KlHzyj1d6DCmTGN10soN5dObXRebgkUsTqAir3k-VgOD7HVGHtDvAKQMp4wCY04Th-bW7VRyKeZ9f67FlOslgYXMz2gZf-9XUR0_ZUTZFv2gWmGlR5y8AOrPYvcRBb5DwJ2FVkjyhtqc_pI7JjbvT3c6r62IhFeI8sk_4aiJZuNs2XI2BR17-miXH_EmLnok7-KrANdhXZwyukgK0EC2eOALOTqsKXOpmaLsoNFMIBVdR0TnZhul3NBwosBV3j2LxecPFIuff2dw3Fzy37OW0WaNJFAUou1Eq_0FWg-nMlkWpICWmgjz-5gNX22r20h_8rKTbxN8u-0BnfKH9DP9WAhtbAG5RghgbGCHPIKkopRd2uJCNFNx3Zx7S1ZraqbumIaBJO7XYxL8X9ko2sbJhiK0cZy8rOj-rkERwFo9EqK7BWn80ED1icto2yH3uk57OqP58LvDQSvOkJbSLAtH8zN3vAD-qjjRyx23wHM-M4bfmkmIfpddBS1LQcSTEOmvvtd1BwWUMMOynOewh45ObOWVbpZPJrdTtVdIA_MQEdBGPdKMJdMGZ8UqCzhcrpDE0LEWV1xWXiryoVfcbsMMsG-7qAf2jAHE2s-EOmFKdTAQcvnoE31Dek1_n2mhXsxV39xetTGavNKjLCXBcCNGQ2ICe-dJAOjFRWoS9if-ZqKfpq1Los2gf75WgynIb8bqJLCZhN10POdvkxOeo-7_JBfkSUq7cVXfRuf82X-773zGtgLyg4WOTKdbYUq4oZuwgyYHMRnUPq98ZI3nXnGBALLtmrsEPfGFV2DpXFPZMm67f0KAoPHuwtp7GKMZP5IcT8P8f1nW7noNHsNg9a7db-QdczH2w-2zVv_wVJt_ca-3vNw26n09rb23ZNCZg52n3z09b_A_m_HoA=

Screenshots

[laFleuere2]

If it helps, I've passed this finding into Claude and it found a potential source of the issue. I can also provide a PR if the findings and fixes sound correct.

For context: At first I found this bug when theorycrafting in PoB with Acolyte of Chayula's Into The Breach with 10 Purple Flames and Twister's Gain +X% - this skill gain never transformed into extra chaos, so I started to dig into PoB calculation, found the potential issue and then tried to replicate it in-game to confirm the bug.

---

In CalcOffence.lua, damage conversion was already a proper two-step process (skill → global), but gain-as-extra was not. buildGainTable() merged skill-tied gains (SkillDamageGainAs…) and global gains (DamageGainAs…/ElementalDamageGainAs…) into a single table, and calcGainedDamage applied all of it at the very end, sourced only from base damage + converted damage.

Consequences:

• Skill-tied gains (Twister's SkillDamageGainAsCold/Fire/Lightning) were effectively computed in step 2, simultaneously with global modifiers.
• Therefore the elemental damage Twister gains could never be a source for a step-2 modifier — neither Into the Breach's "+X% as Chaos" gain nor any conversion. The article says the opposite: because Twister's gain is inherent to the skill, it happens in step 1 and can be converted/gained-from in step 2.

The skill data was already correct — act_dex.lua:9835 tags Twister with SkillDamageGainAsCold/Fire/Lightning. The bug was purely in the order of application, so no data changes were needed

The fix (src/Modules/CalcOffence.lua)

Restructured the engine into a true four-stage pipeline that mirrors the article exactly:

step 1: skill conversion → skill gain → step 2: global conversion → global gain

• Conversion/gain tables are now stored split into .skill and .global (keyed by the Skill mod-name prefix, the existing convention).
• New calcDamageConversionAndGain() helper applies the four stages sequentially on the base-damage vector. Each step's gain is sourced from that step's post-conversion damage, so step-1 gains flow into step-2 conversion and step-2 gain.
• Per-step ≤100% normalization is preserved (steps aren't additive).
• The summation and breakdown were rewritten accordingly; I also fixed a latent landmine in calcDamage's (currently dead) convDst breakdown so it works with the new structure.

Validation

1. Algorithm — ran the actual edited Lua functions against the article's worked examples (real Lua via lupa): Perfect Strike + Avatar of Fire → 950 Fire / 50 Phys; Original Sin + Painter's Servant → 60/20/20 normalization; Perfect Strike + Burning Strikes → 900 Fire; and your case, Twister(+50% Cold) + Into the Breach(+70% as Chaos) → 350 Chaos (old behavior: 0).
2. Regression test — added one to spec/System/TestAttacks_spec.lua (Twister gains Cold via twisterCold, then 100% of Elemental Damage Converted to Chaos converts that gained Cold). It passes on the fix and would fail on the old code.
3. Full suite via the CI Docker image — 365 successes / 0 failures / 0 errors. No regressions.