From 43d741660f6377392a789da76a5cabe62769d5b6 Mon Sep 17 00:00:00 2001
From: ketmar <ketmar@ketmar.no-ip.org>
Date: Fri, 27 Dec 2013 23:07:09 +0200
Subject: [PATCH] shadowcasting sux; back to the basics

---
 src/main.c   |  2 +-
 src/zlight.c | 73 +++++++++++++++++++++++++++++++++++-------------------------
 2 files changed, 44 insertions(+), 31 deletions(-)

diff --git a/src/main.c b/src/main.c
index 5f76382..fa3355c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -308,7 +308,7 @@ static void rebuild_screen (void) {
     render_lights();
     /* sample light */
     //light_dump = 1;
-    for (int tt = 10; tt > 0; --tt) {
+    for (int tt = 20*0+1; tt > 0; --tt) {
       renderlight_sector(light_x, light_y, light_radius, light_as, light_ae, light_color);
     }
     //light_dump = 0;
diff --git a/src/zlight.c b/src/zlight.c
index 3b4303f..f9665ba 100644
--- a/src/zlight.c
+++ b/src/zlight.c
@@ -168,6 +168,9 @@ static void realize_lightmask (void) {
 
 
 ////////////////////////////////////////////////////////////////////////////////
+static int lrad_sqr;
+
+
 static int trace_point_count;
 static struct {
   int x;
@@ -195,6 +198,7 @@ void t_draw_line_no_last (int x0, int y0, int x1, int y1) {
 
 
 static void trace_start (void) {
+  lrad_sqr = lrad*lrad;
   trace_point_count = 0;
   prepare_lightmask();
 }
@@ -228,7 +232,7 @@ static void trace_to_point (int x1, int y1) {
   int dx =  K8ABS(x1-x0), sx = (x0 < x1 ? 1 : -1);
   int dy = -K8ABS(y1-y0), sy = (y0 < y1 ? 1 : -1);
   int err = dx+dy, e2; /* error value e_xy */
-  int ox = x0, oy = y0, dst = lrad*lrad;
+  int ox = x0, oy = y0, dst = lrad_sqr;
   for (;;) {
     if ((x0-lcx)*(x0-lcx)+(y0-lcy)*(y0-lcy) >= dst) {
       trace_add_point(x0, y0);
@@ -323,40 +327,34 @@ static inline int light_is_blocked (int x, int y) {
 }
 
 
+static int lsc_xx, lsc_xy, lsc_yx, lsc_yy;
+
+
 // recursive lightcasting function
-static void light_octant (int cx, int cy, int row, double start, double end, int radius, int octant) {
+static void light_octant (int cx, int cy, int row, double start, double end) {
   if (start >= end) {
-    // multipliers for transforming coordinates to other octants
-    static const int mult[4][8] = {
-      {1, 0, 0,-1,-1, 0, 0, 1},
-      {0, 1,-1, 0, 0,-1, 1, 0},
-      {0, 1, 1, 0, 0,-1,-1, 0},
-      {1, 0, 0, 1,-1, 0, 0,-1},
-    };
-    int xx = mult[0][octant];
-    int xy = mult[1][octant];
-    int yx = mult[2][octant];
-    int yy = mult[3][octant];
-    int radius_sqr = radius*radius;
-    for (int j = row; j <= radius; ++j) {
+    double new_start;
+    double l_slope, r_slope;
+    int dst = lrad_sqr;
+    int xx = lsc_xx, xy = lsc_xy, yx = lsc_yx, yy = lsc_yy;
+    for (int j = row; j <= lrad; ++j) {
       int dx = -j-1;
-      int dy = -j, dysqr = dy*dy;
+      int dy = -j;
+      int dysqr = dy*dy;
       int blocked = 0;
-      double new_start = 666.666;
       int x = cx+dx*xx+dy*xy;
       int y = cy+dx*yx+dy*yy;
       double dyp5 = dy+0.5;
       double dym5 = dy-0.5;
-      while (dx <= 0) {
-        ++dx;
+      while (dx++ <= 0) {
         // translate the dx, dy coordinates into map coordinates
         x += xx;
         y += yx;
         // l_slope and r_slope store the slopes of the left and right
         // extremities of the tile we're considering
-        double l_slope = (dx-0.5)/dyp5;
-        double r_slope = (dx+0.5)/dym5;
+        l_slope = (dx-0.5)/dyp5;
         if (end > l_slope) break;
+        r_slope = (dx+0.5)/dym5;
         if (start >= r_slope) {
           // our light beam is touching this tile; light it
           int blk = light_is_blocked(x, y);
@@ -367,16 +365,18 @@ static void light_octant (int cx, int cy, int row, double start, double end, int
             } else {
               blocked = 0;
               start = new_start;
-              if (dx*dx+dysqr < radius_sqr) lb_light_plot(x, y);
+              if (dx*dx+dysqr < dst) lb_light_plot(x, y);
             }
           } else {
-            if (blk && j < radius) {
-              // this is a blocking tile, start a child scan
-              blocked = 1;
-              light_octant(cx, cy, j+1, start, l_slope, radius, octant);
-              new_start = r_slope;
+            if (blk) {
+              if (j < lrad) {
+                // this is a blocking tile, start a child scan
+                blocked = 1;
+                light_octant(cx, cy, j+1, start, l_slope);
+                new_start = r_slope;
+              }
             } else {
-              if (!blk && dx*dx+dysqr < radius_sqr) lb_light_plot(x, y);
+              if (dx*dx+dysqr < dst) lb_light_plot(x, y);
             }
           }
         }
@@ -402,7 +402,7 @@ static void trace_light (int as, int ae) {
   trace_start();
   if (asx == aex) {
     /* do full circle (square, actually) */
-#if 0
+#if 1
     /* top */
     for (int d = -lrad; d < lrad; ++d) trace_to_point(lcx+d, lcy-lrad);
     /* right */
@@ -412,7 +412,20 @@ static void trace_light (int as, int ae) {
     /* left */
     for (int d = lrad; d > -lrad; --d) trace_to_point(lcx-lrad, lcy+d);
 #else
-    for (int oct = 0; oct < 8; ++oct) light_octant(lcx, lcy, 1, 1.0, 0.0, lrad, oct);
+    // multipliers for transforming coordinates to other octants
+    static const int mult[4][8] = {
+      {1, 0, 0,-1,-1, 0, 0, 1},
+      {0, 1,-1, 0, 0,-1, 1, 0},
+      {0, 1, 1, 0, 0,-1,-1, 0},
+      {1, 0, 0, 1,-1, 0, 0,-1},
+    };
+    for (int oct = 0; oct < 8; ++oct) {
+      lsc_xx = mult[0][oct];
+      lsc_xy = mult[1][oct];
+      lsc_yx = mult[2][oct];
+      lsc_yy = mult[3][oct];
+      light_octant(lcx, lcy, 1, 1.0, 0.0);
+    }
     lb_light_plot(lcx, lcy);
 #endif
   } else {
-- 
2.11.4.GIT