adjust material size for melting for armor parts, weapons, trap components and tools...

docs/changelog.txt

@@ -54,6 +54,7 @@ Template for new versions:
 ## New Tools
 
 ## New Features
+- `tweak`: ``realistic-melting``: change melting return for inorganic armor parts, shields, weapons, trap components and tools to stop smelters from creating metal, bring melt return for adamantine in line with other metals to ~95% of forging cost. wear reduces melt return by 10% per level
 
 ## Fixes
 

docs/plugins/tweak.rst

@@ -53,6 +53,19 @@ Commands
     Names filled waterskins, flasks, and vials according to their contents,
     the same way other containers such as barrels, bins, and cages are named.
     (:bug:`4914`)
+``realistic-melting``
+    Makes amortized metal bar returns for melting uniform across all item types.
+    Affects weapons, shields, armor parts, tools, and trap components. The target
+    amount of metal produced by melting is 95% of the metal used for production
+    of the item. Each level of wear decreases melt return by a further 10%. The game
+    has a fixed granularity of 0.3 for metal bar returns, so individual items will
+    randomly return an amount that may be above or below the target. For example
+    a metal cap with item size 1 will produce 0.9 of a bar with a 16.6% chance of
+    producing an additional 0.3 of a bar. Over time, the average return for melting
+    these types of caps will be ~0.95 of a bar. Calculations for melting return are
+    done for items with base game production cost. Melting return might not be
+    calculated correctly for modded items or items created in custom reactions
+    that don't respect vanilla production costs. (:bug:`6027`)
 ``named-codices``
     Displays titles for books instead of the default material description.
 ``partial-items``

plugins/tweak/tweak.cpp

@@ -17,6 +17,7 @@ using namespace DFHack;
 #include "tweaks/eggs-fertile.h"
 #include "tweaks/fast-heat.h"
 #include "tweaks/flask-contents.h"
+#include "tweaks/material-size-for-melting.h"
 #include "tweaks/named-codices.h"
 #include "tweaks/partial-items.h"
 #include "tweaks/reaction-gloves.h"
@@ -74,6 +75,15 @@ DFhackCExport command_result plugin_init(color_ostream &out, vector<PluginComman
 
     TWEAK_HOOK("reaction-gloves", reaction_gloves_hook, produce);
 
+    TWEAK_HOOK("realistic-melting", material_size_for_melting_armor_hook, getMaterialSizeForMelting);
+    TWEAK_HOOK("realistic-melting", material_size_for_melting_gloves_hook, getMaterialSizeForMelting);
+    TWEAK_HOOK("realistic-melting", material_size_for_melting_shoes_hook, getMaterialSizeForMelting);
+    TWEAK_HOOK("realistic-melting", material_size_for_melting_helm_hook, getMaterialSizeForMelting);
+    TWEAK_HOOK("realistic-melting", material_size_for_melting_pants_hook, getMaterialSizeForMelting);
+    TWEAK_HOOK("realistic-melting", material_size_for_melting_weapon_hook, getMaterialSizeForMelting);
+    TWEAK_HOOK("realistic-melting", material_size_for_melting_trapcomp_hook, getMaterialSizeForMelting);
+    TWEAK_HOOK("realistic-melting", material_size_for_melting_tool_hook, getMaterialSizeForMelting);
+
     return CR_OK;
 }
 

plugins/tweak/tweaks/material-size-for-melting.h

@@ -0,0 +1,69 @@
+#include <cmath>
+
+#include "modules/Materials.h"
+#include "modules/Random.h"
+
+#include "df/inorganic_raw.h"
+#include "df/item_armorst.h"
+#include "df/item_constructed.h"
+#include "df/item_glovesst.h"
+#include "df/item_helmst.h"
+#include "df/item_pantsst.h"
+#include "df/item_shieldst.h"
+#include "df/item_shoesst.h"
+#include "df/item_toolst.h"
+#include "df/item_trapcompst.h"
+#include "df/item_weaponst.h"
+
+struct Mrng {
+    Random::MersenneRNG rng;
+    Mrng() { rng.init(); }
+};
+
+static float get_random() {
+    static Mrng mrng;
+    return static_cast <float> (mrng.rng.drandom1());
+}
+
+static int32_t get_material_size_for_melting(df::item_constructed *item, int32_t base_material_size, float production_stack_size) {
+    const float melt_return_per_material_size = 0.3f, base_melt_recovery = 0.95f, loss_per_wear_level = 0.1f;
+
+    if (item->mat_type != 0) // bail if not INORGANIC
+        return base_material_size;
+
+    float forging_cost_per_item;
+    if (auto inorganic = df::inorganic_raw::find(item->mat_index);
+        inorganic && inorganic->flags.is_set(df::inorganic_flags::DEEP_SPECIAL))
+    {
+        // adamantine items
+        forging_cost_per_item = static_cast<float>(base_material_size) / production_stack_size;
+    } else {
+        // non adamantine items
+        forging_cost_per_item = std::max(std::floor(static_cast<float>(base_material_size) / 3.0f), 1.0f);
+        forging_cost_per_item /= production_stack_size;
+    }
+
+    float calculated_size = forging_cost_per_item / melt_return_per_material_size;
+    float melt_recovery = base_melt_recovery - static_cast<float>(item->wear) * loss_per_wear_level;
+    calculated_size *= melt_recovery;
+    int32_t random_part = ((modff(calculated_size, &calculated_size) > get_random()) ? 1 : 0);
+    return static_cast<int32_t>(calculated_size) + random_part;
+}
+
+#define DEFINE_MATERIAL_SIZE_FOR_MELTING_TWEAK(TYPE, PRODUCTION_STACK_SIZE) \
+struct material_size_for_melting_##TYPE##_hook : df::item_##TYPE##st {\
+    typedef df::item_##TYPE##st interpose_base;\
+    DEFINE_VMETHOD_INTERPOSE(int32_t, getMaterialSizeForMelting, ()) {\
+        return get_material_size_for_melting(this, INTERPOSE_NEXT(getMaterialSizeForMelting)(), PRODUCTION_STACK_SIZE);\
+    }\
+};\
+IMPLEMENT_VMETHOD_INTERPOSE(material_size_for_melting_##TYPE##_hook, getMaterialSizeForMelting);
+
+DEFINE_MATERIAL_SIZE_FOR_MELTING_TWEAK(armor, 1.0f)
+DEFINE_MATERIAL_SIZE_FOR_MELTING_TWEAK(gloves, 2.0f)
+DEFINE_MATERIAL_SIZE_FOR_MELTING_TWEAK(shoes, 2.0f)
+DEFINE_MATERIAL_SIZE_FOR_MELTING_TWEAK(helm, 1.0f)
+DEFINE_MATERIAL_SIZE_FOR_MELTING_TWEAK(pants, 1.0f)
+DEFINE_MATERIAL_SIZE_FOR_MELTING_TWEAK(weapon, 1.0f)
+DEFINE_MATERIAL_SIZE_FOR_MELTING_TWEAK(trapcomp, 1.0f)
+DEFINE_MATERIAL_SIZE_FOR_MELTING_TWEAK(tool, 1.0f)