1 files changed, 156 insertions, 0 deletions
diff --git a/lib/triangle.h b/lib/triangle.h
new file mode 100644
index 0000000..abd697c
--- /dev/null
+++ b/lib/triangle.h
@@ -0,0 +1,156 @@
+#pragma once
+
+#include "config/types.h"
+#include "maths.h"
+#include <glm/glm.hpp>
+
+template<glm::length_t Dim, Arithmetic T, glm::qualifier Q = glm::defaultp>
+struct Triangle : public glm::vec<3, glm::vec<Dim, T, Q>> {
+	using Point = glm::vec<Dim, T, Q>;
+	using Base = glm::vec<3, glm::vec<Dim, T, Q>>;
+	using Base::Base;
+
+	[[nodiscard]] constexpr Point
+	operator*(BaryPosition bari) const
+	{
+		return p(0) + (sideDifference(1) * bari.x) + (sideDifference(2) * bari.y);
+	}
+
+	[[nodiscard]] constexpr Point
+	centroid() const
+	{
+		return [this]<glm::length_t... Axis>(std::integer_sequence<glm::length_t, Axis...>) {
+			return Point {(p(0)[Axis] + p(1)[Axis] + p(2)[Axis]) / 3 ...};
+		}(std::make_integer_sequence<glm::length_t, Dim>());
+	}
+
+	[[nodiscard]] constexpr auto
+	area() const
+		requires(Dim == 3)
+	{
+		return glm::length(crossProduct(sideDifference(1), sideDifference(2))) / T {2};
+	}
+
+	[[nodiscard]] constexpr auto
+	area() const
+		requires(Dim == 2)
+	{
+		return std::abs((sideDifference(1).x * sideDifference(2).y) - (sideDifference(2).x * sideDifference(1).y)) / 2;
+	}
+
+	[[nodiscard]] constexpr Normal3D
+	normal() const
+		requires(Dim == 3)
+	{
+		return crossProduct(sideDifference(1), sideDifference(2));
+	}
+
+	[[nodiscard]] constexpr auto
+	height()
+	{
+		return (area() * 2) / ::distance(p(0), p(1));
+	}
+
+	[[nodiscard]] constexpr Normal3D
+	nnormal() const
+		requires(Dim == 3)
+	{
+		return glm::normalize(normal());
+	}
+
+	[[nodiscard]] constexpr auto
+	sideDifference(glm::length_t side) const
+	{
+		return difference(p(side), p(0));
+	}
+
+	[[nodiscard]] constexpr auto
+	calcSideDifference(glm::length_t side) const
+	{
+		return calcDifference(p(side), p(0));
+	}
+
+	[[nodiscard]] constexpr auto
+	angle(glm::length_t corner) const
+	{
+		return Arc {P(corner), P(corner + 2), P(corner + 1)}.length();
+	}
+
+	template<glm::length_t D = Dim>
+	[[nodiscard]] constexpr auto
+	angleAt(const glm::vec<D, T, Q> pos) const
+		requires(D <= Dim)
+	{
+		for (glm::length_t i {}; i < 3; ++i) {
+			if (glm::vec<D, T, Q> {p(i)} == pos) {
+				return angle(i);
+			}
+		}
+		return 0.F;
+	}
+
+	[[nodiscard]] constexpr auto
+	isUp() const
+	{
+		const auto edgeAB = sideDifference(1);
+		const auto edgeAC = sideDifference(2);
+		return edgeAB.x * edgeAC.y >= edgeAB.y * edgeAC.x;
+	}
+
+	[[nodiscard]] constexpr auto
+	p(const glm::length_t idx) const
+	{
+		return Base::operator[](idx);
+	}
+
+	[[nodiscard]] constexpr auto
+	P(const glm::length_t idx) const
+	{
+		return Base::operator[](idx % 3);
+	}
+
+	[[nodiscard]] constexpr Point *
+	begin()
+	{
+		return &(Base::x);
+	}
+
+	[[nodiscard]] constexpr const Point *
+	begin() const
+	{
+		return &(Base::x);
+	}
+
+	[[nodiscard]] constexpr Point *
+	end()
+	{
+		return begin() + 3;
+	}
+
+	[[nodiscard]] constexpr const Point *
+	end() const
+	{
+		return begin() + 3;
+	}
+
+	[[nodiscard]]
+	constexpr auto
+	positionOnPlane(const glm::vec<2, T, Q> coord2d) const
+		requires(Dim == 3)
+	{
+		const auto edgeCrossProduct = crossProduct(calcSideDifference(1), calcSideDifference(2));
+		return coord2d
+				|| static_cast<T>(
+						((edgeCrossProduct.x * p(0).x) + (edgeCrossProduct.y * p(0).y) + (edgeCrossProduct.z * p(0).z)
+								- (edgeCrossProduct.x * coord2d.x) - (edgeCrossProduct.y * coord2d.y))
+						/ edgeCrossProduct.z);
+	}
+
+	[[nodiscard]]
+	constexpr bool
+	containsPoint(const GlobalPosition2D coord) const
+	{
+		return pointLeftOfOrOnLine(coord, p(0), p(1)) && pointLeftOfOrOnLine(coord, p(1), p(2))
+				&& pointLeftOfOrOnLine(coord, p(2), p(0));
+	}
+};