Fix #188 fade out projectiles in Gothic 1

_work/data/Scripts/Content/GFA/_intern/collision.d

@@ -473,6 +473,35 @@ func void GFA_CC_ProjectileCollisionWithWorld() {
 };
 
 
+/*
+ * Complete the half-implemented feature in Gothic 1 of fading out the visibility of a projectile before removing it.
+ * This function hooks oCAIArrowBase::DoAI(), if the collectable feature is not enabled.
+ */
+func void GFA_CC_FadeProjectileVisibility() {
+    // Check if AI was already removed
+    var int destroyed; destroyed = MEM_ReadInt(EDI);
+    if (destroyed) {
+        return;
+    };
+
+    // Check validity of projectile
+    var int projectilePtr; projectilePtr = EBX; // oCItem*
+    if (!projectilePtr) {
+        return;
+    };
+    var zCVob projectile; projectile = _^(projectilePtr);
+
+    // Check if the projectile stopped moving
+    if (!(projectile.bitfield[0] & zCVob_bitfield0_physicsEnabled)) {
+        var int arrowAI; arrowAI = ESI; // oCAIArrow*
+        var int lifeTime; lifeTime = MEM_ReadInt(arrowAI+oCAIArrowBase_lifeTime_offset);
+        if (lifeTime == -1082130432) { // -1
+            MEM_WriteInt(arrowAI+oCAIArrowBase_lifeTime_offset, FLOATONE);
+        };
+    };
+};
+
+
 /*
  * Disable collision of projectiles with NPCs once the projectiles have bounced off of another surface. This function is
  * called from GFA_ExtendCollisionCheck() only if GFA_COLL_PRIOR_NPC == -1.

_work/data/Scripts/Content/GFA/_intern/init.d

@@ -173,6 +173,9 @@ func void GFA_InitFeatureCustomCollisions() {
     HookEngineF(oCAIArrow__ReportCollisionToAI_hitChc, 6, GFA_CC_ProjectileCollisionWithNpc); // Hit reg/coll on NPCs
     if (GOTHIC_BASE_VERSION == 1) {
         writeNOP(oCAIArrow__ReportCollisionToAI_destroyPrj, 7); // Disable destroying of projectiles
+        if (!(GFA_Flags & GFA_REUSE_PROJECTILES)) {
+            HookEngineF(oCAIArrow__DoAI_rtn, 6, GFA_CC_FadeProjectileVisibility); // Implement fading like in Gothic 2
+        };
         HookEngineF(oCAIArrow__ReportCollisionToAI_collAll, 8, GFA_CC_ProjectileCollisionWithWorld); // Collision world
         MemoryProtectionOverride(oCAIArrow__ReportCollisionToAI_keepPlyStrp, 2); // Keep poly strip after coll
         MEM_WriteByte(oCAIArrow__ReportCollisionToAI_keepPlyStrp, /*EB*/ 235); // jmp