学步园

在网络游戏里，玩家的行走与平时单机版的游戏有着很大的差别，当你按下键盘时，人物角色并不能立即就向前行走，而是需要把它移动的请求发送到服务器，让服务器来作出判断是否可以行走，然后把行走位置通知视野里所有其它玩家，第二人生的客户端就会把这个人物按位置信息显示出来。下面就来分析怎么样发送玩家状态信息给服务器。

 

#001 void LLAppViewer::idle()

#002 {

#003      // Update frame timers

#004      static LLTimer idle_timer;

#005 

#006      LLControlBase::updateAllListeners();

#007 

#008      LLFrameTimer::updateFrameTime();

#009      LLEventTimer::updateClass();

#010      LLCriticalDamp::updateInterpolants();

#011      LLMortician::updateClass();

#012       F32 dt_raw = idle_timer.getElapsedTimeAndResetF32();

#013 

……

#077     

#078          static LLFrameTimer agent_update_timer;

#079          static U32                          last_control_flags;

#080     

#081          //     When appropriate, update agent location to the simulator.

#082          F32 agent_update_time = agent_update_timer.getElapsedTimeF32();

#083          BOOL flags_changed = gAgent.controlFlagsDirty() || (last_control_flags != gAgent.getControlFlags());

#084     

#085          if (flags_changed || (agent_update_time > (1.0f / (F32) AGENT_UPDATES_PER_SECOND)))

#086          {

#087                 // Send avatar and camera info

#088                 last_control_flags = gAgent.getControlFlags();

#089                 send_agent_update(TRUE);

#090                 agent_update_timer.reset();

#091          }

#092      }

#093 ......

#094 }

 

上面第83行获取当前角色的状态是否发生变化，然后通过send_agent_update函数不断地发送状态消息给服务器。接着下来就去分析这个函数，它的代码如下：

#001 void send_agent_update(BOOL force_send, BOOL send_reliable)

#002 {

#003      if (gAgent.getTeleportState() != LLAgent::TELEPORT_NONE)

#004      {

#005             // We don't care if they want to send an agent update, they're not allowed to until the simulator

……

#147 

#148      if (duplicate_count < DUP_MSGS && !gDisconnected)

#149      {

#150             // Build the message

#151             msg->newMessageFast(_PREHASH_AgentUpdate);

#152             msg->nextBlockFast(_PREHASH_AgentData);

#153             msg->addUUIDFast(_PREHASH_AgentID, gAgent.getID());

#154             msg->addUUIDFast(_PREHASH_SessionID, gAgent.getSessionID());

#155             msg->addQuatFast(_PREHASH_BodyRotation, body_rotation);

#156             msg->addQuatFast(_PREHASH_HeadRotation, head_rotation);

#157             msg->addU8Fast(_PREHASH_State, render_state);

#158             msg->addU8Fast(_PREHASH_Flags, flags);

#159 

#160 //          if (camera_pos_agent.mV[VY] > 255.f)

#161 //          {

#162 //                 llinfos << "Sending camera center " << camera_pos_agent << llendl;

#163 //          }

#164            

#165             msg->addVector3Fast(_PREHASH_CameraCenter, camera_pos_agent);

#166             msg->addVector3Fast(_PREHASH_CameraAtAxis, gCamera->getAtAxis());

#167             msg->addVector3Fast(_PREHASH_CameraLeftAxis, gCamera->getLeftAxis());

#168             msg->addVector3Fast(_PREHASH_CameraUpAxis, gCamera->getUpAxis());

#169             msg->addF32Fast(_PREHASH_Far, gAgent.mDrawDistance);

#170            

#171             msg->addU32Fast(_PREHASH_ControlFlags, control_flags);

#172 

#173             if (gDebugClicks)

#174             {

#175                    if (control_flags & AGENT_CONTROL_LBUTTON_DOWN)

#176                    {

#177                           llinfos << "AgentUpdate left button down" << llendl;

#178                    }

#179 

#180                    if (control_flags & AGENT_CONTROL_LBUTTON_UP)

#181                    {

#182                           llinfos << "AgentUpdate left button up" << llendl;

#183                    }

#184             }

#185 

#186             gAgent.enableControlFlagReset();

#187 

#188             if (!send_reliable)

#189             {

#190                    gAgent.sendMessage();

#191             }

#192             else

#193             {

#194                    gAgent.sendReliableMessage();

#195             }

#196 

#197             //llinfos << "agent " << avatar_pos_agent << " cam " << camera_pos_agent << llendl;

#198 

#199             // Copy the old data

#200             last_head_rot = head_rotation;

#201             last_render_state = render_state;

#202             last_camera_pos_agent = camera_pos_agent;

#203             last_camera_at = gCamera->getAtAxis();

#204             last_camera_left = gCamera->getLeftAxis();

#205             last_camera_up = gCamera->getUpAxis();

#206             last_control_flags = control_flags;

#207             last_flags = flags;

#208      }

#209 }

#210 

 

在上面的代码里，就调用msg消息对象创建状态消息，然后通过sendMessage和sendReliableMessage函数发送给服务器，这样在服务器的玩家角色就会更新状态，如果行走的话，也会得到更新的。第二人生里的消息结构是根据XML模板来构造的，这个部分的功能也比较复杂。