From d7fe4af1e9fcce1f601e31242dec51a9fec1a788 Mon Sep 17 00:00:00 2001
From: Zeno Rogue <zeno@attnam.com>
Date: Fri, 27 Jan 2023 11:16:34 +0100
Subject: [PATCH] embeddings:: implemented the cylinderHE embedding

---
 embeddings.cpp   | 35 ++++++++++++++++++++++++++++++++++-
 geometry2.cpp    |  4 ++++
 nonisotropic.cpp |  4 ++++
 3 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/embeddings.cpp b/embeddings.cpp
index 08dfa780..2a31f5c9 100644
--- a/embeddings.cpp
+++ b/embeddings.cpp
@@ -183,6 +183,23 @@ EX namespace geom3 {
             g = ginf[gSpace534].g;
             g.gameplay_dimension = 2;
             }
+
+          if(spatial_embedding == seCylinderHE && ieuclid) {
+            g.kind = gcProduct;
+            g.homogeneous_dimension--;
+            g.sig[2] = -1;
+            }
+
+          if(spatial_embedding == seCylinderHoro && ieuclid) {
+            g.kind = gcProduct;
+            g.homogeneous_dimension--;
+            g.sig[2] = -1;
+            }
+
+          if(spatial_embedding == seCylinderNil && ieuclid) {
+            g = ginf[gNil].g;
+            g.gameplay_dimension = 2;
+            }
           }
         }
       }
@@ -562,6 +579,21 @@ struct emb_euc_cylinder : emb_euclid_noniso {
     }
   };
 
+struct emb_euc_cylinder_he : emb_euc_cylinder {
+  bool no_spin() override { return true; }
+  transmatrix get_lsti() override { return cspin90(0, 2); }
+  hyperpoint actual_to_intermediate(hyperpoint a) override {
+    ld z0 = zlevel(a);
+    a /= exp(z0);
+    ld y0 = atan2(a[1], a[0]);
+    ld x0 = asin_auto(hypot(a[0], a[1]));
+    return hyperpoint(x0-1, y0, z0, 1);
+    }
+  transmatrix intermediate_to_actual_translation(hyperpoint i) override {
+    return zpush(i[2]) * cspin(1, 0, i[1]) * xpush(i[0]);
+    }
+  };
+
 struct emb_euc_in_sph : emb_euclid_noniso {
   bool is_euc_in_sph() override { return true; }
   ld center_z() override { return 1; }
@@ -646,7 +678,7 @@ EX unique_ptr<embedding_method> make_embed() {
   if(!embedded_plane)
     emb1 = new emb_none;
   else if(any_cylinder(spatial_embedding) && mgclass() == gcEuclid)
-    emb1 = new emb_euc_cylinder;
+    emb1 = spatial_embedding == seCylinderHE ? new emb_euc_cylinder_he : new emb_euc_cylinder;
   else if(mgclass() == ggclass())
     emb1 = new emb_same_in_same;
   else if(mgclass() == gcSphere && among(ggclass(), gcHyperbolic, gcEuclid))
@@ -933,6 +965,7 @@ void embedding_method::auto_configure() {
   if(spatial_embedding == seProductS) configure_cylinder();
   if(spatial_embedding == seCylinderE) configure_cylinder();
   if(spatial_embedding == seCylinderH) configure_cylinder();
+  if(spatial_embedding == seCylinderHE) configure_cylinder();
   }
 
 }
diff --git a/geometry2.cpp b/geometry2.cpp
index 7a4cab7e..44bb5021 100644
--- a/geometry2.cpp
+++ b/geometry2.cpp
@@ -241,6 +241,8 @@ void horo_distance::become(hyperpoint h1) {
     a = 0, b = hdist(h1, C0);
   else if(cgi.emb->is_euc_in_product())
     a = 0, b = hdist(h1, C0);
+  else if(cgi.emb->is_cylinder())
+    a = 0, b = hdist(h1, tile_center());
   else
     a = 0, b = intval(h1, tile_center());
   }
@@ -253,6 +255,8 @@ horo_distance::horo_distance(shiftpoint h1, const shiftmatrix& T) {
   if(sn::in() || mhybrid || nil || sl2) become(inverse_shift(T, h1));
   else if(cgi.emb->is_euc_in_product())
     a = 0, b = hdist(h1.h, unshift(T * tile_center(), h1.shift));
+  else if(cgi.emb->is_cylinder())
+    a = 0, b = hdist(h1.h, unshift(T * tile_center(), h1.shift));
   else
     a = 0, b = intval(h1.h, unshift(T * tile_center(), h1.shift));
   }
diff --git a/nonisotropic.cpp b/nonisotropic.cpp
index be839dfe..4aedad5a 100644
--- a/nonisotropic.cpp
+++ b/nonisotropic.cpp
@@ -1374,6 +1374,10 @@ EX namespace hybrid {
         dynamicval<eGeometryClass> dgc(cginf.g.kind, cginf.g.sig[2] < 0 ? gcHyperbolic : gcSphere);
         return f();
         }
+      if(cgi.emb->is_cylinder()) {
+        dynamicval<eGeometryClass> dgc(cginf.g.kind, cginf.g.sig[2] < 0 ? gcHyperbolic : gcSphere);
+        return f();
+        }
       geom3::light_flip(true);
       finalizer ff([] { geom3::light_flip(false); });
       return f();