From d4dcc4ec9815f1574eb12b3ee20aa0362f77704b Mon Sep 17 00:00:00 2001
From: Javier Sancho <jsf@jsancho.org>
Date: Tue, 27 Aug 2019 20:09:18 +0200
Subject: [PATCH] Voronoi mesh relax

---
 dungeon-master/geom/point.scm   | 20 ++++++++++++++++++-
 dungeon-master/geom/voronoi.scm | 34 +++++++++++++++++++++++++++++----
 2 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/dungeon-master/geom/point.scm b/dungeon-master/geom/point.scm
index 64faaac..3f471eb 100644
--- a/dungeon-master/geom/point.scm
+++ b/dungeon-master/geom/point.scm
@@ -4,7 +4,9 @@
             point?
             point-x
             point-y
-	    points-distance))
+	    points-distance
+            sum-points
+            scale-point))
 
 (define-record-type <point>
   (make-point x y)
@@ -16,3 +18,19 @@
   (abs
    (sqrt (+ (expt (- (point-x p1) (point-x p2)) 2)
             (expt (- (point-y p1) (point-y p2)) 2)))))
+
+(define (sum-points . points-to-sum)
+  (let loop ((points points-to-sum)
+             (x 0)
+             (y 0))
+    (cond ((null? points)
+           (make-point x y))
+          (else
+           (loop (cdr points)
+                 (+ x (point-x (car points)))
+                 (+ y (point-y (car points))))))))
+
+(define (scale-point point scale)
+  (make-point
+   (* (point-x point) scale)
+   (* (point-y point) scale)))
diff --git a/dungeon-master/geom/voronoi.scm b/dungeon-master/geom/voronoi.scm
index 9217285..66acf9e 100644
--- a/dungeon-master/geom/voronoi.scm
+++ b/dungeon-master/geom/voronoi.scm
@@ -32,6 +32,14 @@
       (> (angle-sign seed c1 c2) 0)))
   (make-raw-voronoi-region seed (list-sort compare-angles vertices)))
 
+(define (voronoi-region-center region)
+  (let* ((vertices (voronoi-region-vertices region))
+         (centers (map (lambda (v) (triangle-center v)) vertices)))
+    (scale-point
+     (apply sum-points centers)
+     (/ 1 (length vertices)))))
+
+
 ;;; Voronoi mesh
 
 (define-record-type <voronoi-mesh>
@@ -42,7 +50,7 @@
   (frame voronoi-mesh-frame)
   (regions voronoi-mesh-regions))
 
-(define* (make-voronoi-mesh vertices #:optional (relax-steps 3))
+(define (make-voronoi-mesh vertices)
   ;; Delaunay triangulation
   (receive (triangles points frame)
       (bowyer-watson vertices)
@@ -86,9 +94,27 @@
                   ordered-regions)))
     filtered-regions))
 
-(define* (voronoi-mesh-relax voronoi #:optional (to-relax '()))
-  (let ((regions (partitioning voronoi)))
-    voronoi))
+(define* (voronoi-mesh-relax voronoi #:optional (points-to-relax '()))
+  (let ((regions
+         (map
+          (lambda (r) (cons (voronoi-region-seed r) (voronoi-region-center r)))
+          (partitioning voronoi)))
+        (points
+         (filter
+          (lambda (p) (not (member p (voronoi-mesh-frame voronoi))))
+          (voronoi-mesh-points voronoi)))
+        (to-relax
+         (if (null? points-to-relax)
+             (voronoi-mesh-points voronoi)
+             points-to-relax)))
+    (make-voronoi-mesh
+     (map
+      (lambda (point)
+        (let ((center (assoc-ref regions point)))
+          (if (and center (member point to-relax))
+              center
+              point)))
+      points))))
 
 (define (make-regions points triangles)
   (map-in-order
-- 
2.39.2