Fixed: Clientside mobjs on moving planes

The server will now tell clients when a mobj is
on the floor so that it knows when it can rely on
its local plane Z heights for placing the objects.

Fixes Z coord flickering for remote mobjs on
moving planes.

doomsday/engine/portable/include/sv_pool.h

@@ -89,6 +89,7 @@ typedef enum {
 #define MDFC_TRANSLUCENCY       0x040000 // Mobj has translucency.
 #define MDFC_FADETARGET         0x080000 // Mobj is fading to/from visible/invisible
 #define MDFC_TYPE               0x100000 // Mobj type specified in delta.
+#define MDFC_ON_FLOOR           0x200000 // Mobj Z is floorZ.
 
 // Extra flags for the Extra Flags byte.
 #define MDFE_FAST_MOM           0x01 // Momentum has 10.6 bits (+/- 512)

doomsday/engine/portable/src/cl_mobj.c

@@ -749,19 +749,33 @@ void ClMobj_ReadDelta2(boolean skip)
     }
     if(df & MDF_POS_Z)
     {
-        d->pos[VZ] = FIX2FLT((Msg_ReadShort() << FRACBITS) | (Msg_ReadByte() << 8));
-        if(info)
+        if(!(moreFlags & MDFE_Z_FLOOR))
         {
-            info->flags |= CLMF_KNOWN_Z;
+            d->pos[VZ] = FIX2FLT((Msg_ReadShort() << FRACBITS) | (Msg_ReadByte() << 8));
+            if(info)
+            {
+                info->flags |= CLMF_KNOWN_Z;
+
+                // The mobj won't stick if an explicit coordinate is supplied.
+                info->flags &= ~(CLMF_STICK_FLOOR | CLMF_STICK_CEILING);
+            }
+            d->floorZ = Msg_ReadFloat();
+        }
+        else
+        {
+            // Ignore these.
+            Msg_ReadShort();
+            Msg_ReadByte();
+            Msg_ReadFloat();
 
-            // The mobj won't stick if an explicit coordinate is supplied.
-            info->flags &= ~(CLMF_STICK_FLOOR | CLMF_STICK_CEILING);
+            info->flags |= CLMF_KNOWN_Z;
+            d->pos[VZ] = d->floorZ;
         }
 
-        d->floorZ = Msg_ReadFloat();
         d->ceilingZ = Msg_ReadFloat();
     }
 
+    /*
     // When these flags are set, the normal Z coord is not included.
     if(moreFlags & MDFE_Z_FLOOR)
     {
@@ -775,6 +789,7 @@ void ClMobj_ReadDelta2(boolean skip)
         if(info)
             info->flags |= CLMF_KNOWN_Z;
     }
+    */
 
     // Momentum using 8.8 fixed point.
     if(df & MDF_MOM_X)
@@ -872,12 +887,14 @@ void ClMobj_ReadDelta2(boolean skip)
         }
     }
 
+    /*
     if(df & (MDF_POS_X | MDF_POS_Y | MDF_POS_Z) ||
        moreFlags & (MDFE_Z_FLOOR | MDFE_Z_CEILING))
     {
         // This'll update floorz and ceilingz.
         ClMobj_CheckPlanes(mo, justCreated);
     }
+    */
 
     // If the clmobj is Hidden (or Nulled), it will not be linked back to
     // the world until it's officially Created. (Otherwise, partially updated

doomsday/engine/portable/src/sv_frame.c

@@ -228,6 +228,13 @@ void Sv_WriteMobjDelta(const void* deltaPtr)
         moreFlags |= MDFE_FADETARGET;
     }
 
+    // On the floor?
+    if(df & MDFC_ON_FLOOR)
+    {
+        df |= MDF_MORE_FLAGS;
+        moreFlags |= MDFE_Z_FLOOR;
+    }
+
     // Mobj type?
     if(df & MDFC_TYPE)
     {
@@ -239,6 +246,7 @@ void Sv_WriteMobjDelta(const void* deltaPtr)
     if(d->selector & ~DDMOBJ_SELECTOR_MASK)
         df |= MDF_SELSPEC;
 
+    /*
     // Floor/ceiling z?
     if(df & MDF_POS_Z)
     {
@@ -249,6 +257,7 @@ void Sv_WriteMobjDelta(const void* deltaPtr)
             moreFlags |= (d->pos[VZ] == DDMINFLOAT ? MDFE_Z_FLOOR : MDFE_Z_CEILING);
         }
     }
+    */
 
 #ifdef _DEBUG
     if(df & MDFC_NULL)

doomsday/engine/portable/src/sv_pool.c

@@ -580,7 +580,15 @@ boolean Sv_RegisterCompareMobj(cregister_t* reg, const mobj_t* s,
     if(r->pos[VY] != s->pos[VY])
         df |= MDF_POS_Y;
     if(r->pos[VZ] != Sv_GetMaxedMobjZ(s) || r->floorZ != s->floorZ || r->ceilingZ != s->ceilingZ)
+    {
         df |= MDF_POS_Z;
+        if(!(df & MDFC_CREATE) && s->pos[VZ] <= s->floorZ)
+        {
+            // It is currently on the floor. The client will place it on its
+            // clientside floor and disregard the Z coordinate.
+            df |= MDFC_ON_FLOOR;
+        }
+    }
 
     if(r->mom[MX] != s->mom[MX])
         df |= MDF_MOM_X;