A port of the example sector/portal renderer here.
After seeing the video that describes the renderer, I got interested in seeing how it accomplished so much in a short amount of C code. (and to be clear, this is the simple solid shaded renderer from the video, not the impressive final one with textures, and lighting using lightmaps baked from the author's own radiosity implementation).
I enjoy working with rendering code, and this style is very different from other renderers I've looked at, which makes it enticing.
Porting the code to Nim is more of a sideshow. I like Nim, and something like this port is ideal because I already have graphics utility modules from other projects that I can use for quick experimentation.
prender.c is the C version taken from here.
map-clear.txt is the map provided by original author
for use by prender.c.
sdl2 is the pinned version of the Nim SDL2 bindings I'm using.
Get Nim from here. I'm using version 0.20.2, but earlier versions back to 0.18 should probably work.
To pull in the external source dependencies under [vendor][vendor/], run:
$ git submodule update --init --recursive
You need the development packages for both SDL 1.2 (for the original), and SDL 2 (for the port).
To compile the original:
$ gcc -o dist/prender prender.c -lSDL -lm
The port:
$ nim build
To compile the original, technically this works:
$ gcc -o dist/prender prender.c -lSDL -lm
But as to how to get the GCC or Clang based compiler and the SDL 1.2/2 libraries and headers
for your platform, you're own your own. I will note that for the port, on Windows the binding
library expects the SDL2 library to be named SDL2.dll, and on MacOS, libSDL2.dylib. You might
have to rename them, depending on how you get/compile SDL2.
To compile the port:
$ nim build
All versions expect to be run from the dist directory, which contains map data, and other files loaded at runtime.
- W: Move forward
- S: Move backward
- A: Sidestep left
- D: Sidestep right
- Move the mouse to look around
- T: Go into debug mode where only one sector is drawn at a time. When in this mode
TABwill draw the next queued sector. Prints debugging messages to stdout for each sector, and when all sectors are done. - Escape or Q - quit
The port is fairly straightforward, where I tried to keep the C semantics, while staying true to Nim idioms. I copied over most comments.
Notes from the port:
-
Changed from SDL1 to SDL2. Both are up to the task. This was only in anticipation of using some helper code I have for SDL2 in modified versions from the basic port.
-
Changed the bottom wall base color from a magenta to a shade of green for a contrast I can see better.
-
I changed the map parsing code from
scanf()to parsing functions similar to and from the Nimparseutilsmodule. Requires noticably more code than the original. You could probably get closer to original with thestrscansmodule, but I couldn't be assed to do the conversion. -
I changed growable arrays managed with
realloc()to use Nim seqs instead. -
I included a
geommodule I wrote for vector math. This is the only obviously gratuitous change I made in the port, since its only use at the moment is to provide the definitions of 2 and 3 element vectors. No operations are used. I might try to change the inline operations to using the module operations at some point, just to see if it makes a difference in runtime. -
Changed the queue implementation in
DrawScreento use indices into the backing array rather than pointers to the entries. Nim makes pointer arithmetic verbose compared to C, so it was an easy choice. Also made local templates for the queue functions, to avoid a little repetition. -
Added mouse warping to center of the screen so the cursor won't stray out of the window when looking around, and turned off the cursor.
-
I disabled numeric overflow/underflow checks in DrawScreen, as they do happen, but are clamped by the code. I may narrow this down just to the sections of the code where the overflows occur, just to see what difference it makes rest of the rendering, speed-wise.
-
I left the globals as globals, even though that may pucker some rectums. It's a single file implementation of a renderer. It's fine.
-
There are a couple of glitches that are common to the original port. Which I suppose is a good sign the port is correct. You can step outside of the level at corners. And on the top floor, at certain angles you can see a white wall appear and disappear when you're standing to the right of the stairs.
- On the top floor, at certain positions right of the stairs, a bright white wall is rendered when facing a certain angle. Both the original and the port do this.
I'll probably experiment with some changes to the port. I'll put significant changes in their own subdirectories, to avoid fouling up the basic port, which I want to leave as a clean starting point.
Some possibilities:
-
Figure out what the rendering glitch on the top floor is coming from. I see it in the original and the port.
-
OpenGL support, similar to what Ken Silverman did with Polymost for the Build engine, but I want to see if I can figure it out without looking at the code in the JonoF Build engine port. We'll see how long my resolve lasts. I suspect that getting this working simplifies things if you want to add sprites later, since you can use the z-buffer to composite sprites in after the level is rendered. With the usual complications for transparent walls and decals.
-
One thought I had looking at the data structures for the map sectors is that it has some passing similarities with a nav mesh. It's not optimimzed for the least number of polygons, but it would be interesting to see how well you can put the level geometry to that use without adding any other information. I haven't searched, but it wouldn't surprise me if the Build engine games did that.