Learning Diary #10: Lua, socket server, path finding, quaternions

12/Jul/2010

Using Lua and a Socket Server to test and debug iPhone Games

Damn, too many balloons. Ops, just change the Lua code real time!

I already talked about #iDevBlogADay. But let’s say it again: I just love this “group”! The first thing I do when I wake up is checking the feed for the day’s articles. And how sad I get if an author hadn’t published his take yet.

Everyday we get 2 new nice articles from fellow indie (or established or beginners – like me)  game developers. One of these articles “Tweak Away” from Mystery Coconut brings Lua and socket servers into your iPhone game development.

Main points you’ll learn from the article:

• How to open a debug server for your game.
• How to integrate Lua into your game and how it can access your game elements.
• Change your game behaviors and state via command line (e.g.: no more re-compiling to change the speed of a ball).
• Scripting all of your game content and behavior.

And yes, Miguel makes everything that easy for us :)

Path Finding

• Path finding class for a RTS game: ASIPathFinder. “ASIPathFinder is a complete implementation of a cooperative path finding algorithm, and will probably be most useful for writing Real Time Strategy games. It is written in Objective-C, and is compatible with Mac OS and iPhone OS.”
• Cocos2D, Path finding and Tile maps – sample app: cool working code which I found on Cocos2D forums.

Cocos2D

• RenderTexture: let’s explain via an example: for a shooter game which leaves bullet holes, we could use sprites for these holes, but a RenderTexture is memory saver.
  a) Sprites: 500 holes – 500 sprites – 1000 triangles – 2000 vertexes.
  b) RenderTexture: will draw only one sprite – it takes a picture and work in that picture.
• EAGLView: create the OpenGL context.

Drawing with Quartz2D

1. Save current context
2. Perform a single combined matrix transformation
3. Draw graphics to this transformation
4. Restore context

Source: Beginning iPhone Games Development

Quaternion

• Sum of a scalar and a vector
• The quotient of two vectors
• Imaginary number: i * i = -1
• A quaterion is a complex number extension: 3 numbers all square roots of -1: i, j, k
• j * j = -1, k * k  = -1
• q = w + xi + yj + zk (w = real, x, y, z = complex).
• or q = [w, v] (w = scalar, v = (x,y,z) – vector)

Source: http://www.gamedev.net/reference/articles/article1095.asp, http://www.paradeofrain.com/2010/07/lessons-learned-in-tilt-controls/