From 8a70efed05880195c53b71021331155a6c113cf2 Mon Sep 17 00:00:00 2001
From: Jonathan Westhues <jwesthues@cq.cx>
Date: Tue, 1 Jul 2008 20:32:24 -0800
Subject: [PATCH] Make sliver triangle tests work on the minimum altitude, not
 on area.

[git-p4: depot-paths = "//depot/solvespace/": change = 1816]
---
 mesh.cpp     |  6 +++---
 polygon.cpp  | 10 +++++++++-
 polygon.h    |  1 +
 solvespace.h |  2 +-
 util.cpp     |  5 +----
 wishlist.txt |  1 +
 6 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/mesh.cpp b/mesh.cpp
index 586fba28..b41e05a1 100644
--- a/mesh.cpp
+++ b/mesh.cpp
@@ -67,8 +67,8 @@ void SMesh::Simplify(int start) {
     int i, j;
     for(i = start; i < l.n; i++) {
         STriangle *tr = &(l.elem[i]);
-        if((tr->Normal()).Magnitude() < LENGTH_EPS*LENGTH_EPS) {
-            tr->tag = 0;
+        if(tr->MinAltitude() < LENGTH_EPS) {
+            tr->tag = 1;
         } else {
             tr->tag = 0;
         }
@@ -171,7 +171,7 @@ void SMesh::Simplify(int start) {
 
         for(i = 0; i < convc - 2; i++) {
             STriangle tr = STriangle::From(meta, conv[0], conv[i+1], conv[i+2]);
-            if((tr.Normal()).Magnitude() > LENGTH_EPS*LENGTH_EPS) {
+            if(tr.MinAltitude() > LENGTH_EPS) {
                 tout[toutc++] = tr;
             }
         }
diff --git a/polygon.cpp b/polygon.cpp
index 06555692..57914020 100644
--- a/polygon.cpp
+++ b/polygon.cpp
@@ -5,9 +5,17 @@ Vector STriangle::Normal(void) {
     return ab.Cross(bc);
 }
 
+double STriangle::MinAltitude(void) {
+    double altA = a.DistanceToLine(b, c.Minus(b)),
+           altB = b.DistanceToLine(c, a.Minus(c)),
+           altC = c.DistanceToLine(a, b.Minus(a));
+
+    return min(altA, min(altB, altC));
+}
+
 bool STriangle::ContainsPoint(Vector p) {
     Vector n = Normal();
-    if(n.Magnitude() < LENGTH_EPS*LENGTH_EPS) {
+    if(MinAltitude() < LENGTH_EPS) {
         // shouldn't happen; zero-area triangle
         return false;
     }
diff --git a/polygon.h b/polygon.h
index fafe332e..54b84aaa 100644
--- a/polygon.h
+++ b/polygon.h
@@ -124,6 +124,7 @@ public:
     static STriangle From(STriMeta meta, Vector a, Vector b, Vector c);
     Vector Normal(void);
     void FlipNormal(void);
+    double MinAltitude(void);
     int WindingNumberForPoint(Vector p);
     bool ContainsPoint(Vector p);
     bool ContainsPointProjd(Vector n, Vector p);
diff --git a/solvespace.h b/solvespace.h
index 8fea9c0d..d0b1cf93 100644
--- a/solvespace.h
+++ b/solvespace.h
@@ -24,7 +24,7 @@ inline int WRAP(int v, int n) {
 #define ZERO(v) memset((v), 0, sizeof(*(v)))
 #define CO(v) (v).x, (v).y, (v).z
 
-#define LENGTH_EPS  (0.0000001)
+#define LENGTH_EPS  (1e-7)
 
 #define isforname(c) (isalnum(c) || (c) == '_' || (c) == '-' || (c) == '#')
 
diff --git a/util.cpp b/util.cpp
index eccfbd9a..ea9c5040 100644
--- a/util.cpp
+++ b/util.cpp
@@ -269,10 +269,7 @@ Vector Vector::From(hParam x, hParam y, hParam z) {
 }
 
 bool Vector::Equals(Vector v) {
-    if(fabs(x - v.x) > LENGTH_EPS) return false;
-    if(fabs(y - v.y) > LENGTH_EPS) return false;
-    if(fabs(z - v.z) > LENGTH_EPS) return false;
-    return true;
+    return (this->Minus(v)).Magnitude() < LENGTH_EPS;
 }
 
 Vector Vector::Plus(Vector b) {
diff --git a/wishlist.txt b/wishlist.txt
index 21508c2b..e0ca8716 100644
--- a/wishlist.txt
+++ b/wishlist.txt
@@ -8,6 +8,7 @@ auto-generate circles and faces when lathing
 copy the section geometry to other end when sweeping
 cylindrical faces
 draw explicit edges
+symmetric about line segment
 
 
 long term