Physics: Fix grenade bouncing down slopes

[Baker]

Grenades in Quake don't bounce down slopes and in multiplayer often they get stuck and vibrate annoyingly in places. DarkPlaces has sv_gameplayfix_grenadebouncedownslopes which repairs this and R00k implemented this in Qrack and a custom ProQuake server long ago. This is adapted from Qrack's implementation.

Implementing

1. Create a cvar called sv_gameplayfix_grenadebouncedownslopes and register it. A value of 0 is original Quake behavior obviously.
2. Open sv_physics.c and find this:

Code: Select all

// stop if on ground
   if (trace.plane.normal[2] > 0.7)
   {
      if (ent->v.velocity[2] < 60 || ent->v.movetype != MOVETYPE_BOUNCE)
      {
         ent->v.flags = (int)ent->v.flags | FL_ONGROUND;
         ent->v.groundentity = EDICT_TO_PROG(trace.ent);
         VectorCopy (vec3_origin, ent->v.velocity);
         VectorCopy (vec3_origin, ent->v.avelocity);
      }
   }

And replace with:

Code: Select all

// stop if on ground
   if (trace.plane.normal[2] > 0.7)
   {
      int stop_moving = false;
      if (sv_gameplayfix_grenadebouncedownslopes.value)
      {
         if (DotProduct(trace.plane.normal, ent->v.velocity) < 60)
            stop_moving = true;
      }
      else
      {
         if (ent->v.velocity[2] < 60 || ent->v.movetype != MOVETYPE_BOUNCE)
            stop_moving = true;
      }

      if (stop_moving)
      {
         ent->v.flags = (int)ent->v.flags | FL_ONGROUND;
         ent->v.groundentity = EDICT_TO_PROG(trace.ent);
         VectorCopy (vec3_origin, ent->v.velocity);
         VectorCopy (vec3_origin, ent->v.avelocity);
      }
   }

Disclaimer: I'm not Mr. Physics but have interest in this feature mostly because I find grenades getting stuck in multiplayer annoying and like R00k's fix.

[r00k]

Looking in to whats there currently, I find

Code: Select all

   VectorScale (ent->v.velocity, host_frametime, move);
   trace = SV_PushEntity (ent, move);
   if (trace.fraction == 1)
      return;
   if (ent->free)
      return;

   if (ent->v.movetype == MOVETYPE_BOUNCE)
      backoff = 1.5;
   else if (ent->v.movetype == MOVETYPE_BOUNCEMISSILE)
      backoff = 2.0;
   else
      backoff = 1;

   ClipVelocity (ent->v.velocity, trace.plane.normal, ent->v.velocity, backoff);

// stop if on ground
   //R00k: fixed by LordHavoc
   d = DotProduct(trace.plane.normal, ent->v.velocity);
   if (trace.plane.normal[2] > 0.5 && fabs(d) < 15)//R00k changed so dm6 grenade ramp doesnt stick as much..
   {
      ent->v.flags = (int)ent->v.flags | FL_ONGROUND;
      ent->v.groundentity = EDICT_TO_PROG(trace.ent);
      ClipVelocity (ent->v.velocity, trace.plane.normal, ent->v.velocity, backoff + (trace.plane.normal[2]));
   }
   else
      ent->v.flags = (int)ent->v.flags & ~FL_ONGROUND;
   


I havent tested this with gibs, though i feel they should roll like normal

[Baker]

//R00k changed so dm6 grenade ramp doesnt stick as much..

That was where I was doing my testing ... And I kind of felt that the grenades should more reliably bounce. I see you messed with that. hehe