From 064864eac61e936af909470fcccc5c67ef6d3169 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sun, 11 Aug 2024 19:32:23 +0100
Subject: Calculate centre and size of mesh, wrap it all in a Dimensions object

---
 gfx/models/mesh.cpp | 27 +++++++++++++++++++++++++--
 gfx/models/mesh.h   | 51 ++++++++++++++++++++++++---------------------------
 2 files changed, 49 insertions(+), 29 deletions(-)

(limited to 'gfx/models')

diff --git a/gfx/models/mesh.cpp b/gfx/models/mesh.cpp
index 1b6ecda..2eae160 100644
--- a/gfx/models/mesh.cpp
+++ b/gfx/models/mesh.cpp
@@ -1,10 +1,33 @@
 #include "mesh.h"
 
-MeshBase::MeshBase(GLsizei m_numIndices, GLenum mode, std::pair<RelativePosition3D, RelativePosition3D> minmax) :
-	m_numIndices {m_numIndices}, mode {mode}, min {minmax.first}, max {minmax.second}
+MeshBase::MeshBase(GLsizei m_numIndices, GLenum mode, const std::vector<RelativePosition3D> & positions) :
+	m_numIndices {m_numIndices}, mode {mode}, dimensions {positions}
 {
 }
 
+MeshBase::Dimensions::Dimensions(const std::span<const RelativePosition3D> positions) :
+	Dimensions {positions, {extents(positions, 0), extents(positions, 1), extents(positions, 2)}}
+{
+}
+
+MeshBase::Dimensions::Dimensions(
+		const std::span<const RelativePosition3D> positions, const std::array<Extents1D, 3> & extents1ds) :
+	minExtent(extents1ds[0].min, extents1ds[1].min, extents1ds[2].min),
+	maxExtent(extents1ds[0].max, extents1ds[1].max, extents1ds[2].max), centre {(minExtent + maxExtent) / 2.0F},
+	size {std::ranges::max(positions | std::views::transform([this](const auto & v) {
+		return glm::distance(v, centre);
+	}))}
+{
+}
+
+MeshBase::Dimensions::Extents1D
+MeshBase::Dimensions::extents(const std::span<const RelativePosition3D> positions, glm::length_t D)
+{
+	return std::ranges::minmax(positions | std::views::transform([D](const auto & v) {
+		return v[D];
+	}));
+}
+
 void
 MeshBase::Draw() const
 {
diff --git a/gfx/models/mesh.h b/gfx/models/mesh.h
index f6a1bd2..8791aed 100644
--- a/gfx/models/mesh.h
+++ b/gfx/models/mesh.h
@@ -4,6 +4,7 @@
 #include "gfx/gl/vertexArrayObject.h"
 #include <glArrays.h>
 #include <glad/gl.h>
+#include <ranges>
 #include <span>
 #include <stdTypeDefs.h>
 
@@ -11,35 +12,46 @@ class Vertex;
 
 class MeshBase {
 public:
+	class Dimensions {
+	public:
+		using Extents1D = std::ranges::minmax_result<RelativeDistance>;
+		explicit Dimensions(const std::span<const RelativePosition3D>);
+
+		RelativePosition3D minExtent, maxExtent;
+		RelativePosition3D centre;
+		RelativeDistance size;
+
+	private:
+		Dimensions(const std::span<const RelativePosition3D>, const std::array<Extents1D, 3> &);
+		static Extents1D extents(const std::span<const RelativePosition3D>, glm::length_t D);
+	};
+
 	void Draw() const;
 	void DrawInstanced(GLuint vao, GLsizei count, GLuint base = 0) const;
 
-	auto
-	minExtent() const
+	[[nodiscard]] const Dimensions &
+	getDimensions() const
 	{
-		return min;
-	}
-
-	auto
-	maxExtent() const
-	{
-		return max;
+		return dimensions;
 	}
 
 protected:
-	MeshBase(GLsizei m_numIndices, GLenum mode, std::pair<RelativePosition3D, RelativePosition3D> minmax);
+	MeshBase(GLsizei m_numIndices, GLenum mode, const std::vector<RelativePosition3D> &);
 
 	glVertexArray m_vertexArrayObject;
 	glBuffers<2> m_vertexArrayBuffers;
 	GLsizei m_numIndices;
 	GLenum mode;
-	RelativePosition3D min, max;
+	Dimensions dimensions;
 };
 
 template<typename V> class MeshT : public MeshBase, public ConstTypeDefs<MeshT<V>> {
 public:
 	MeshT(const std::span<const V> vertices, const std::span<const unsigned int> indices, GLenum mode = GL_TRIANGLES) :
-		MeshBase {static_cast<GLsizei>(indices.size()), mode, extent(vertices)}
+		MeshBase {static_cast<GLsizei>(indices.size()), mode,
+				materializeRange(vertices | std::views::transform([](const auto & v) {
+					return static_cast<RelativePosition3D>(v.pos);
+				}))}
 	{
 		VertexArrayObject::data(vertices, m_vertexArrayBuffers[0], GL_ARRAY_BUFFER);
 		VertexArrayObject::data(indices, m_vertexArrayBuffers[1], GL_ARRAY_BUFFER);
@@ -51,21 +63,6 @@ public:
 	{
 		return vao.addAttribsFor<V>(m_vertexArrayBuffers[0]).addIndices(m_vertexArrayBuffers[1]);
 	}
-
-	static auto
-	extent(const std::span<const V> vertices)
-	{
-		std::pair<decltype(V::pos), decltype(V::pos)> out {};
-		for (glm::length_t D {}; D < 3; ++D) {
-			const auto mm
-					= std::minmax_element(vertices.begin(), vertices.end(), [D](const auto & va, const auto & vb) {
-						  return va.pos[D] < vb.pos[D];
-					  });
-			out.first[D] = mm.first->pos[D];
-			out.second[D] = mm.second->pos[D];
-		}
-		return out;
-	}
 };
 
 using Mesh = MeshT<Vertex>;
-- 
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