cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   AcesWild
   Member

   Hi.

   My desire is to take some text, and scale it towards the screen on the Z axis. So, I have derived a new class from CCBitmapFontAtlas, I added a scheduled method (to change the Z axis scale factor) and an update method to do the scaling.

   Just for a test, I have overridden the draw method like this

   -(void) draw
   {
      DEBUG_NSLOG(@"\n m_scaleFactor = %f", m_scaleFactor);
      glScalef(1, 1, -100);
   
      [super draw];
   }

   I have verified that my overridden method does get called, but there is absolutely no sclaing taking place.

   Im definitely doing something wrong as I am pretty new to cocos2d and I am definitely an openGL n00b.

   Any help please?

   Posted 1 year ago #
2. 

   JunoMan
   Member

   There is no perspective scaling in Cocos2d as it uses a parallel projection matrix.

   To do what you want to do you need to calculate the appropriate scaling factor and set the X and Y to that.

   From memory I think its something like.

   float scale_x = 1/m_scaleFactor;
   float scale_y = 1/m_scaleFactor;
   glScalef(scale_x, scale_y, 1);

   m_scaleFactor is effectively your Z distance.

   The bigger the m_scaleFactor, the smaller and further away the sprite will seem. (You'll need to check for 0.0 of course)

   More here http://en.wikibooks.org/wiki/Build_a_3D_Engine

   Posted 1 year ago #
3. 

   araker
   Moderator

   To get this working you need a 3d projection, depthbuffer and a vertexZ value bigger or smaller than 0. Also you don't want everything to be effected by the scale, that's where the push and pop is for.

   -(void) draw
   {
      DEBUG_NSLOG(@"\n m_scaleFactor = %f", m_scaleFactor);
      glPushMatrix();
      glScalef(1, 1, -100);
   
      [super draw];
      glPopMatrix();
   }

   I'm not sure though if this is going to give you the effect you want.

   Edit, I think you should go for junoman's suggestion.

   Posted 1 year ago #
4. 

   hm50
   Member

   I am by no means at the level of JunoMan or Araker, but wouldn't a simple CCScaleTo action work? Or myText.scale = x?

   Just ignore me if I am way off base...lol

   Posted 1 year ago #
5. 

   AcesWild
   Member

   I was afraid you guys were going to say something to that effect.
   I kne I could do the scale on the X and Y axis, but was hoping to do a "true" zoom...however, the scale on the X and Y worked pretty well, and it also let me use already built actions which definitely made it easier for me.

   Thanks for the help!

   Posted 1 year ago #

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