EU7 scenery format and models streaming

scene/eu7/eu7_section.h

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+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <utility>
+
+#include <glm/glm.hpp>
+
+namespace scene::eu7 {
+
+// Musi byc zgodne z scene::EU07_SECTIONSIZE / EU07_REGIONSIDESECTIONCOUNT.
+constexpr int kSectionSizeM { 1000 };
+constexpr int kRegionSideSectionCount { 500 };
+
+[[nodiscard]] std::pair<int, int>
+section_row_column( glm::dvec3 const &world_location );
+
+[[nodiscard]] std::size_t
+section_index( glm::dvec3 const &world_location );
+
+[[nodiscard]] std::size_t
+section_index( int const row, int const column );
+
+} // namespace scene::eu7