子弹跟踪目标逻辑实现

条件：已知子弹位置，子弹速度大小m_nSpd、方向m_nAngle，目标的位置，每次转角角度FOLLOW_ANGLE

实现目标：要求子弹跟踪目标，且角度能够平滑地过度到正对目标

实现：

1、算出子弹与目标所成的角度nAngle

2、（ANGLE_CIRCLE=360）

            if(m_nAngle != nAngle){
                if(nAngle > m_nAngle){
                    if(nAngle < m_nAngle + 180){
                        m_nAngle += FOLLOW_ANGLE;
                        if(m_nAngle-FOLLOW_ANGLE <= nAngle && m_nAngle >= nAngle)
                            m_nAngle = nAngle;
                    }
                    else/* if (nAngle >= m_nAngle + 180)*/{
                        m_nAngle -= FOLLOW_ANGLE;
                        if(m_nAngle <= 0 && -m_nAngle >= ANGLE_CIRCLE-nAngle)
                            m_nAngle = nAngle;
                    }
                }
                else{
                    if(m_nAngle < nAngle + 180){
                        m_nAngle -= FOLLOW_ANGLE;
                        if(m_nAngle <= nAngle && m_nAngle+FOLLOW_ANGLE>=nAngle)
                            m_nAngle = nAngle;
                    }
                    else{
                        m_nAngle += FOLLOW_ANGLE;
                        if(m_nAngle >= ANGLE_CIRCLE && m_nAngle - ANGLE_CIRCLE >= nAngle){
                            m_nAngle = nAngle;
                        }
                    }
                }
            }