interpolation: handle specific effect deltas

This resolves various TR1 and TR2 effects jittering in 60fps.
LostArtefacts · Feb 28, 2025 · 93e723d · 93e723d
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commit 93e723d
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Showing 2 changed files with 35 additions and 3 deletions.
diff --git a/docs/tr1/CHANGELOG.md b/docs/tr1/CHANGELOG.md
@@ -3,6 +3,7 @@
 - changed the Controls screen to hide the reset and unbind texts when changing a key (#2103)
 - fixed several instances of the camera going out of bounds (#1034)
 - fixed issues with fixed cameras in 60 FPS shifting before settling on their target (#1186)
+- fixed missiles from mutants/centaurs/Natla jittering in 60 FPS (#1314)
 - fixed the bear AI fix option being applied in the Vilcabamba demo (#2559, regression from 4.8)
 
 ## [4.8.3](https://github.com/LostArtefacts/TRX/compare/tr1-4.8.2...tr1-4.8.3) - 2025-02-17

diff --git a/src/libtrx/game/interpolation.c b/src/libtrx/game/interpolation.c
@@ -88,6 +88,36 @@ static XYZ_32 M_GetItemMaxDelta(const ITEM *const item)
     return (XYZ_32) { .x = max_xz, .y = max_y, .z = max_xz };
 }
 
+static XYZ_32 M_GetEffectMaxDelta(const EFFECT *const effect)
+{
+    int32_t max_xz = 128;
+    int32_t max_y = MAX(128, effect->fall_speed * 2);
+    switch (effect->object_id) {
+#if TR_VERSION == 1
+    case O_MISSILE_1:
+    case O_MISSILE_3:
+        max_xz = 220;
+        break;
+    case O_MISSILE_2:
+        max_xz = 250;
+        break;
+#else
+    case O_MISSILE_FLAME:
+        max_xz = 200;
+        break;
+    case O_MISSILE_KNIFE:
+    case O_MISSILE_HARPOON:
+        max_xz = 150;
+        break;
+#endif
+
+    default:
+        break;
+    }
+
+    return (XYZ_32) { .x = max_xz, .y = max_y, .z = max_xz };
+}
+
 bool Interpolation_IsEnabled(void)
 {
     return m_IsEnabled && M_GetFPS() == 60;
@@ -204,9 +234,10 @@ void Interpolation_Commit(void)
     int16_t effect_num = Effect_GetActiveNum();
     while (effect_num != NO_EFFECT) {
         EFFECT *const effect = Effect_Get(effect_num);
-        INTERPOLATE(effect, pos.x, ratio, 128);
-        INTERPOLATE(effect, pos.y, ratio, MAX(128, effect->fall_speed * 2));
-        INTERPOLATE(effect, pos.z, ratio, 128);
+        const XYZ_32 max_delta = M_GetEffectMaxDelta(effect);
+        INTERPOLATE(effect, pos.x, ratio, max_delta.x);
+        INTERPOLATE(effect, pos.y, ratio, max_delta.y);
+        INTERPOLATE(effect, pos.z, ratio, max_delta.z);
         INTERPOLATE_ROT(effect, rot.x, ratio, DEG_45);
         INTERPOLATE_ROT(effect, rot.y, ratio, DEG_45);
         INTERPOLATE_ROT(effect, rot.z, ratio, DEG_45);