From b1e99acaab3f14dd9397badc5d0049db1d44b7e4 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 29 Oct 2024 14:03:40 +1000
Subject: [PATCH] geom/tri: add `inclusive` test for points

---
 cruft/util/geom/tri.cpp | 26 ++++++++++++++++++++++++++
 cruft/util/geom/tri.hpp | 22 ++++++++++++++++------
 2 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/cruft/util/geom/tri.cpp b/cruft/util/geom/tri.cpp
index 7c4cdea1..3e379839 100644
--- a/cruft/util/geom/tri.cpp
+++ b/cruft/util/geom/tri.cpp
@@ -7,3 +7,29 @@
  */
 
 #include "tri.hpp"
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename T>
+bool
+cruft::geom::inclusive (tri2<T> const &obj, point2<T> const &p)
+{
+    // Assumes ccw winding
+    CHECK (cross (obj.b - obj.a, obj.c - obj.a) > 0);
+
+    auto const sign = [] (
+        cruft::point2f const p_,
+        cruft::point2f const a_,
+        cruft::point2f const b_)
+    {
+        return cross (p_ - a_, b_ - a_);
+    };
+
+    return  sign (p, obj.a, obj.b) <= 0
+        and sign (p, obj.b, obj.c) <= 0
+        and sign (p, obj.c, obj.a) <= 0;
+}
+
+
+//-----------------------------------------------------------------------------
+template bool cruft::geom::inclusive (tri2<f32> const&, point2<f32> const&);
diff --git a/cruft/util/geom/tri.hpp b/cruft/util/geom/tri.hpp
index 19a1d9a7..970d3b20 100644
--- a/cruft/util/geom/tri.hpp
+++ b/cruft/util/geom/tri.hpp
@@ -6,8 +6,7 @@
  * Copyright 2016-2018 Danny Robson <danny@nerdcruft.net>
  */
 
-#ifndef CRUFT_GEOM_TRI_HPP
-#define CRUFT_GEOM_TRI_HPP
+#pragma once
 
 #include "../point.hpp"
 #include "sample/fwd.hpp"
@@ -15,13 +14,16 @@
 #include <cstddef>
 #include <random>
 
+
 namespace cruft::geom {
     ///////////////////////////////////////////////////////////////////////////
     template <size_t S, typename T>
     struct tri {
         tri () = default;
-        tri (point<S,T> _a, point<S,T> _b, point<S,T> _c):
-            a (_a), b (_b), c (_c)
+        tri (point<S,T> _a, point<S,T> _b, point<S,T> _c)
+            : a (_a)
+            , b (_b)
+            , c (_c)
         { ; }
 
         cruft::point<S,T> a, b, c;
@@ -30,6 +32,10 @@ namespace cruft::geom {
     template <size_t S, typename T>
     tri (point<S,T>, point<S,T>, point<S,T>) -> tri<S,T>;
 
+    template <typename T> using tri2 = tri<2, T>;
+    template <typename T> using tri3 = tri<3, T>;
+
+    using tri2f = tri<2,float>;
     using tri3f = tri<3,float>;
 
 
@@ -120,6 +126,10 @@ namespace cruft::geom {
     {
         return area (tri (a, b, c));
     }
-};
 
-#endif
+
+    //-------------------------------------------------------------------------
+    template <typename T>
+    bool
+    inclusive (tri2<T> const &obj, point2<T> const &p);
+};