Deflektor clone for Camputers Lynx – in progress

This game writing business has taken a little more time that I had hoped!  I lost time last weekend, after I decided to adjust my approach to the ray tracing.  

Originally, I did a ray tracing search at the resolution of the board squares.  This returned a list of square centre positions, so I could draw the ray.  This is what I showed in previous screenshots.

This suffered subtle problems when the ray went off-screen, because the search terminated before the path stepped off-screen, so the user could not see where the ray ended up, it would just end at the final mirror!

Also, to make the screen repaint handling easier, I decided I wanted to XOR plot the ray.   This meant writing a line-drawing routine.  I initially started a Bresenham algorithm, but abandoned this when I realised that rolling the search and line-drawing into one would be a great idea.

Here’s what it looks like now:

deflektor7

The ray tracing search MkII is now high-resolution, and steps in units of 2 pixels, in the direction of travel.  At each step we XOR plot the point on screen.  When we intersect the centre-piece of a mirror, we re-direct the ray.  Similarly, intersecting the centre of other objects allows their specific actions to take place.  The ray tracing terminated when:

  • The ray length exceeds the maximum allowed (overextension).
  • The ray is directed off-screen.
  • The ray hits a wall
  • The ray hits a POD or an MINE.

This is currently wrapped in a Lynx BASIC program that calls two assembly language modules, and I have a playable demo!

Not everything is done yet – there are other objects I have yet to implement.

This then needs wrapping with a title screen, scoring, energy loss, and so forth.

… And I need some levels defining!

Jonathan

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