PL-EarlyC

Early C 3D Software Renderer Public Domain Source Release by EMMIR 2018-2022

demo88.mp4

The code here is an early C implementation of PiSHi LE. PiSHi LE is a subset of the integer-only 3D graphics library used in King's Crook, a software rendered game.

Check out the real time version here: https://github.com/LMP88959/PL-68000

General Info:

This code is written for an early C compiler for the Motorola 68000 processor. (an old version of the Portable C Compiler from around 1981). Along with an assembler and linker from the same time period. -- Side note: even though the Portable C Compiler supports the void type, structure assignment, and enums, I don't use them in this code.

I modified the compiler a bit to add special handling for inline ASM and interrupt service routines. I also stripped any support for floats or doubles from it.

The assembled code runs on a modified Motorola 68000 emulator which I also stripped of floating point support.

The program interacts with simulated hardware components through memory mapped I/O.

Hardware components I'm simulating are a clock, keyboard, terminal and a VDC (Video Device Controller) -- a simple 256/true color video card.

Unlike PL3D-KC, this release is not as general as it utilizes 16-bit operations where necessary to improve speed since the 68000 does not support hardware 32-bit math operations.

Purpose:

Seeing how C looked back in its early days. Learning about the interesting features of early C.

Main things to notice are:

• K&R function declarations
• A function declaration was only necessary when its return type was not int (I kept unneeded decls so the reader could easily see what functions exist)
• B-style initialization support (e.g x 0;)
• Old assignment operator (e.g =<< instead of <<=, or =+ instead of +=)
• Heavy use of implied-integer type whenever a type is not explicitly written.
• Auto (local) variables must be declared at top of scope.
• No void type.
• Six character external symbol limit (for linking).
• No fancy preprocessing, only #define and #include
• Octal literals with 8 and 9 were legal and were interpreted as 010 and 011 respectively.
• Struct member names are global for all structs.
• You can use an arrow operator -> to access first member of a struct on (for example) an integer to access memory at that location. ex:

  struct { int iaddr; };  ... 0720->iaddr = 0;
  

  The above is the same as

  *((int *)0720) = 0;
  

Feature List:

• N-gon rendering (not limited to triangles)
• Depth (Z) buffering
• Flat polygon filling
• Affine texture mapped polygon filling
• Near plane clipping
• Viewport clipping
• Back face culling
• Immediate mode interface
• Matrix stack for transformations
• Code to generate a box
• Indexed or true color rendering

External Resources:

https://spin0r.wordpress.com/2014/11/21/kr-c/

https://news.ycombinator.com/item?id=10165007

Contact Me:

YouTube channel and Discord server for my game King's Crook:

YouTube: https://www.youtube.com/c/LMP88

Discord: https://discord.gg/hdYctSmyQJ