From 4102debac6fc9bcc58091ead007dbce47b42c712 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 20 Jul 2024 12:19:12 +0100
Subject: Calculate and store the extents of a mesh

---
 gfx/models/mesh.h | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

(limited to 'gfx/models/mesh.h')

diff --git a/gfx/models/mesh.h b/gfx/models/mesh.h
index 248cb8f..f6a1bd2 100644
--- a/gfx/models/mesh.h
+++ b/gfx/models/mesh.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "config/types.h"
 #include "gfx/gl/vertexArrayObject.h"
 #include <glArrays.h>
 #include <glad/gl.h>
@@ -13,19 +14,32 @@ public:
 	void Draw() const;
 	void DrawInstanced(GLuint vao, GLsizei count, GLuint base = 0) const;
 
+	auto
+	minExtent() const
+	{
+		return min;
+	}
+
+	auto
+	maxExtent() const
+	{
+		return max;
+	}
+
 protected:
-	MeshBase(GLsizei m_numIndices, GLenum mode);
+	MeshBase(GLsizei m_numIndices, GLenum mode, std::pair<RelativePosition3D, RelativePosition3D> minmax);
 
 	glVertexArray m_vertexArrayObject;
 	glBuffers<2> m_vertexArrayBuffers;
 	GLsizei m_numIndices;
 	GLenum mode;
+	RelativePosition3D min, max;
 };
 
 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}
+		MeshBase {static_cast<GLsizei>(indices.size()), mode, extent(vertices)}
 	{
 		VertexArrayObject::data(vertices, m_vertexArrayBuffers[0], GL_ARRAY_BUFFER);
 		VertexArrayObject::data(indices, m_vertexArrayBuffers[1], GL_ARRAY_BUFFER);
@@ -37,6 +51,21 @@ 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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