frustum object

src/typed-geometry/types/objects/frustum.hh

+#pragma once
+
+#include <typed-geometry/feature/assert.hh>
+
+#include <typed-geometry/functions/swizzling/swizzling-basic.hh>
+#include <typed-geometry/functions/vector/dot.hh>
+#include <typed-geometry/functions/vector/length.hh>
+#include <typed-geometry/functions/vector/normalize.hh>
+#include <typed-geometry/types/scalars/default.hh>
+#include "../pos.hh"
+#include "../vec.hh"
+#include "plane.hh"
+
+namespace tg
+{
+template <class ScalarT>
+struct frustum;
+
+// Common frustum types
+
+using ffrustum = frustum<f32>;
+
+using dfrustum = frustum<f64>;
+
+// ======== IMPLEMENTATION ========
+
+template <class ScalarT>
+struct frustum
+{
+    // frustum represented by 6 planes
+    array<tg::plane<3, ScalarT>, 6> planes;
+
+    constexpr frustum() = default;
+    explicit constexpr frustum(array<tg::plane<3, ScalarT>, 6> const& planes) : planes(planes)
+    { /* TG_CONTRACT(..); */
+    }
+
+    // extract frustum from a view-projection-matrix (proj * view)
+    explicit constexpr frustum(mat<4, 4, ScalarT> const& m)
+    {
+        // computing planes in order: left, right, bottom, top, near, far
+        for (auto i = 0u; i < 3; ++i)
+            for (auto j = 0u; j < 2; ++j)
+            {
+                // plane parameters from matrix (see http://www8.cs.umu.se/kurser/5DV051/HT12/lab/plane_extraction.pdf)
+                vec4 abcd;
+                for (auto k = 0; k < 4; ++k)
+                    abcd[k] = j == 0 ? m[k][3] + m[k][i] : m[k][3] - m[k][i];
+
+                auto n = vec3(abcd);
+                auto l = length(n);
+                planes[2 * i + j] = plane3(dir3(n / l), -abcd.w / l);
+            }
+    }
+
+    [[nodiscard]] bool operator==(frustum const& rhs) const
+    {
+        for (auto i = 0u; i < planes.size(); ++i)
+        {
+            if (planes[i] != rhs.planes[i])
+                return false;
+        }
+        return true;
+    }
+    [[nodiscard]] bool operator!=(frustum const& rhs) const { return !operator==(rhs); }
+};
+
+template <class I, int D, class ScalarT, class TraitsT>
+constexpr void introspect(I&& i, frustum<ScalarT>& v)
+{
+    i(v.planes, "planes");
+}
+
+} // namespace tg