render: Reimplement rendering engine using functional combinators.

Warning: This is a huge commit.

I completely gutted the old scene graph and replaced it with a somewhat
monadic rendering combinator module instead.  The interface remains
purely functional, but replaces the <model> data type with procedures in
the rendering monad instead.  This opens the door for
rendering *anything*, not just meshes.  Now I can implement particle
systems and other non-static things.

1 files changed, 8 insertions, 10 deletions

diff --git a/sly/game.scm b/sly/game.scm
index 7e4a79c..ef92e90 100644
--- a/sly/game.scm
+++ b/sly/game.scm
@@ -35,7 +35,6 @@
   #:use-module (sly math vector)
   #:use-module (sly window)
   #:use-module (sly render)
-  #:use-module (sly render scene)
   #:export (draw-hook
             after-game-loop-error-hook
             run-game-loop
@@ -67,13 +66,13 @@ for the given STACK and error KEY with additional arguments ARGS."
                         (tick-rate 60)
                         (max-ticks-per-frame 4))
   "Run the game loop.  SCENE is a signal which contains the current
-scene to render.  FRAME-RATE specifies the optimal number of frames to
-draw SCENE per second.  TICK-RATE specifies the optimal game logic
-updates per second.  Both FRAME-RATE and TICK-RATE are 60 by default.
-MAX-TICKS-PER-FRAME is the maximum number of times the game loop will
-update game state in a single frame.  When this upper bound is reached
-due to poor performance, the game will start to slow down instead of
-becoming completely unresponsive and possibly crashing."
+scene renderer procedure.  FRAME-RATE specifies the optimal number of
+frames to draw SCENE per second.  TICK-RATE specifies the optimal game
+logic updates per second.  Both FRAME-RATE and TICK-RATE are 60 by
+default.  MAX-TICKS-PER-FRAME is the maximum number of times the game
+loop will update game state in a single frame.  When this upper bound
+is reached due to poor performance, the game will start to slow down
+instead of becoming completely unresponsive and possibly crashing."
   (let ((tick-interval  (interval tick-rate))
         (frame-interval (interval frame-rate))
         (gfx            (make-graphics)))
@@ -84,8 +83,7 @@ becoming completely unresponsive and possibly crashing."
         (gl-viewport 0 0 (vx size) (vy size)))
       (gl-clear (clear-buffer-mask color-buffer depth-buffer))
       (run-hook draw-hook dt alpha)
-      (with-graphics gfx
-                     (draw-scene (signal-ref scene) gfx))
+      (with-graphics gfx ((signal-ref scene) gfx))
       (SDL:gl-swap-buffers))
 
     (define (update lag)