3d:: a system for drawing transparent things, with sorting being the responsibility of HR

hyper.h

@@ -2090,6 +2090,9 @@ enum class PPR {
   MINEMARK, ARROW,
   MOBILE_ARROW,
   LINE, 
+  // in depth tested models transparent surfaces need to be depth sorted by HyperRogue
+  // and set to PPR::TRANSPARENT to draw them after all the opaque ones
+  TRANSPARENT,
   // no depth testing for SUPERLINE and above
   SUPERLINE, TEXT, CIRCLE,
   MAX,
@@ -2832,6 +2835,7 @@ struct textureinfo {
 struct drawqueueitem {
   PPR prio;
   color_t color;
+  int subprio;
   virtual void draw() = 0;
   virtual void draw_back() {}
   virtual void draw_pre() {}

polygons.cpp

@@ -1515,6 +1515,12 @@ void drawqueue() {
         < xintval(ap2.V * xpush0(.1));
       });
 
+  for(PPR p: {PPR::TRANSPARENT})
+    sort(&ptds[qp0[int(p)]], &ptds[qp[int(p)]], 
+      [] (const unique_ptr<drawqueueitem>& p1, const unique_ptr<drawqueueitem>& p2) {
+        return p1->subprio > p2->subprio;
+        });
+
   profile_stop(3);
 
 #if CAP_SDL