From 29c7faa264e1d521030f1238ae81c13f79755f2c Mon Sep 17 00:00:00 2001
From: Zeno Rogue <zeno@attnam.com>
Date: Sat, 9 May 2020 18:33:37 +0200
Subject: [PATCH] stretch < -1 (seems not to be working correctly)

---
 geom-exp.cpp     |  2 +-
 nonisotropic.cpp | 14 +++++++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/geom-exp.cpp b/geom-exp.cpp
index a9a179eb..dbd489a2 100644
--- a/geom-exp.cpp
+++ b/geom-exp.cpp
@@ -843,7 +843,7 @@ EX void showEuclideanMenu() {
         XLAT(
           "Stretch the metric along the fibers. This can currently be done in rotation spaces and in 8-cell, 24-cell and 120-cell. "
           "Value of 0 means not stretched, -1 means S2xE or H2xE (works only in the limit). "
-          "Only the raycaster is implemented for stretched geometry, so you will see only walls."
+          "Only the raycaster is implemented for stretched geometry, so you will see only walls. (Must be > -1)"
           )
         );
       dialog::reaction = ray::reset_raycaster;
diff --git a/nonisotropic.cpp b/nonisotropic.cpp
index 59ea8ce9..4acb1139 100644
--- a/nonisotropic.cpp
+++ b/nonisotropic.cpp
@@ -2082,12 +2082,20 @@ EX namespace stretch {
     return translate(at) * vel;
     }
   
+  EX ld squared() {
+    return abs(1 + factor);
+    }
+
+  EX ld not_squared() {
+    return sqrt(squared());
+    }
+  
   hyperpoint isometric_to_actual(const hyperpoint at, const hyperpoint velocity) {
-    return mulz(at, velocity, 1/sqrt(1+factor));
+    return mulz(at, velocity, 1/not_squared());
     }
   
   hyperpoint actual_to_isometric(const hyperpoint at, const hyperpoint velocity) {
-    return mulz(at, velocity, sqrt(1+factor));
+    return mulz(at, velocity, not_squared());
     }
   
   hyperpoint christoffel(const hyperpoint at, const hyperpoint velocity, const hyperpoint transported) {
@@ -2227,7 +2235,7 @@ EX namespace nisot {
         auto fix = [&] (hyperpoint& h, ld& m) {
           h = stretch::itranslate(at) * h;
           h[3] = 0;
-          ld m1 = h[0] * h[0] + h[1] * h[1] + h[2] * h[2] * (1 + stretch::factor);
+          ld m1 = h[0] * h[0] + h[1] * h[1] + h[2] * h[2] * stretch::squared();
           h /= sqrt(m1/m);
           h = stretch::translate(at) * h;
           };