Thursday, 12 November 2015

Getting ready to render!

A few more hours tonight on the port. Good progress.

The focus was on the dynamic data structures; how they are built, what their relationships are, and how they are used. As a result I've updated the disassembly with more accurate and descriptive labels and comments, including some of the work done by others that preceded me.

The good news is that I now understand most of what is required to render a screen. The game builds a table of (simple) sprites to be rendered; the first 2 are the player, the next 2 are special objects, and the remaining (up to 36) comprise background, then foreground sprites. I'll go into more detail in another post.

The bad news is that each sprite has a pre-render routine that fiddles bits and bytes in the sprite rendering table, and at this point I don't know what half the bytes in the table do. That said, I haven't even attempted to reverse-engineer them just yet.

Next session I'll complete the coding of the data structure building in C, and then start on the actual rendering just to see what falls out without the per-sprite data fiddling. I don't think it'll be long before I have something that vaguely resembles a proper screen!

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