Alien wave pattern - how to?

That's not too difficult, you just have to make all the little steps.

For the wave pattern concentrate on one alien for now, having a movement path. Let the path be several frames, with each frame being a relative movement in a specific direction.

For example:

struct tPathFrame
{
  vector2       m_vDistance;
  float         m_fFrameLength;
};

typedef std::vector   tMovementPath;
   

Now you can store any predefined paths in an array or vector or a list. Give every alien an ID to the path entry. Every alien also needs an Update with the elapes time.

For example:

class CAlien
{
  public:

    vector2   m_vecPos;

    int       m_iPathID;
    int       m_iCurrentPathFrame;
    float     m_fCurrentFramePos;
     
    CAlien() :
      m_iPathID( 0 ),
      m_iCurrentPathFrame( 0 ),
      m_fCurrentFramePos( 0.0f )
    {
    }

    void Update( float fElapsedTime )
    {
      tMovementPath&   MyPath = .....

      while ( fElapsedTime > 0.0f )
      {
        // retrieve current Path Frame

        tPathFrame&  Frame = MyPath[m_iCurrentPathFrame];

        if ( fElapsedTime >= Frame.m_fFrameLength - fCurrentFramePos )
        {
          // move to Frame end position

          m_vecPos += ( Frame.m_fFrameLength - fCurrentFramePos ) / Frame.m_fFrameLength * Frame.m_vDistance;
          
          // this Frame is done

          fCurrentFramePos = 0.0f;
          m_iCurrentPathFrame++;
          if ( m_iCurrentPathFrame >= MyPath.size() )
          {
            // reached the end, loop

            m_iCurrentPathFrame = 0;
          }
          
          // adjust remaining time

          fElapsedTime -= Frame.m_fFrameLength - fCurrentFramePos;
        }
        else
        {
          // move

          m_vecPos += fElapsedTime / Frame.m_fFrameLength * Frame.m_vDistance;

          fCurrentFramePos += fElapsedTime;
          fElapsedTime = 0.0f;
        }
      }
              
    }
};
 

This is pseudo code out of my head, it misses safety checks and maybe got an error or two, but should show the general direction.

[edited by - Endurion on April 15, 2004 3:33:44 AM]

[edited by - Endurion on April 15, 2004 3:34:30 AM]

Yep, that''s how I''d do it. I''d also use bool arrays to define the initial formations of the alien ships, and then just assign them paths, as Endurion said.

Cool. That''s pretty much what I had figured. Thanks for the help!

"There is no dark side of the moon." - Pink Floyd