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

LMP88959 / PL-EarlyC