frame interp: fix obj_fchain

src/d/actor/d_a_obj_fchain.cpp

@@ -10,6 +10,8 @@
 #include "JSystem/J3DGraphBase/J3DDrawBuffer.h"
 #include "SSystem/SComponent/c_math.h"
 #include "d/d_com_inf_game.h"
+#include "dusk/frame_interpolation.h"
+#include "dusk/settings.h"
 #include <cstring>
 
 static char const l_arcName[] = "Fchain";
@@ -65,6 +67,10 @@ int daObjFchain_c::create() {
             local_48++;
         }
         rv = cPhs_COMPLEATE_e;
+#if TARGET_PC
+        mChainInterpPrevValid = false;
+        mChainInterpCurrValid = false;
+#endif
         break;
     }
     return rv;
@@ -289,6 +295,26 @@ void daObjFchain_shape_c::draw() {
     }
 }
 
+#if TARGET_PC
+static void fchain_interp_callback(bool isSimFrame, void* pUserWork) {
+    static_cast<daObjFchain_c*>(pUserWork)->onInterpCallback();
+}
+
+void daObjFchain_c::onInterpCallback() {
+    if (!mChainInterpPrevValid || !mChainInterpCurrValid) {
+        return;
+    }
+
+    const f32 alpha = dusk::frame_interp::get_interpolation_step();
+
+    for (int i = 0; i < CHAIN_COUNT; i++) {
+        const cXyz& p0 = mChainInterpPrev[i];
+        const cXyz& p1 = mChainInterpCurr[i];
+        field_0x694[i] = p0 + (p1 - p0) * alpha;
+    }
+}
+#endif
+
 int daObjFchain_c::draw() {
     if (field_0x584 != 0) {
         g_env_light.settingTevStruct(0, &current.pos, &tevStr);
@@ -297,6 +323,19 @@ int daObjFchain_c::draw() {
             return 1;
         }
         dComIfGd_getOpaListDark()->entryImm(&mShape, 0);
+
+#if TARGET_PC
+        if (dusk::getSettings().game.enableFrameInterpolation) {
+            if (mChainInterpCurrValid) {
+                memcpy(mChainInterpPrev, mChainInterpCurr, sizeof(mChainInterpCurr));
+                mChainInterpPrevValid = true;
+            }
+
+            memcpy(mChainInterpCurr, field_0x694, sizeof(mChainInterpCurr));
+            mChainInterpCurrValid = true;
+            dusk::frame_interp::add_interpolation_callback(&fchain_interp_callback, this);
+        }
+#endif
     }
     return 1;
 }