From a46fded5d93487974ac5f40ff36c8c0f4f7a9db2 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 4 Nov 2023 11:21:23 +0000
Subject: Static helper for loading ASCII grid data

---
 game/terrain2.cpp     | 16 ++++++++++------
 game/terrain2.h       |  5 ++++-
 test/test-terrain.cpp |  2 +-
 3 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/game/terrain2.cpp b/game/terrain2.cpp
index d1af221..105eb33 100644
--- a/game/terrain2.cpp
+++ b/game/terrain2.cpp
@@ -3,7 +3,8 @@
 #include <glm/gtx/intersect.hpp>
 #include <maths.h>
 
-TerrainMesh::TerrainMesh(const std::filesystem::path & input)
+TerrainMesh
+TerrainMesh::loadFromAsciiGrid(const std::filesystem::path & input)
 {
 	size_t ncols = 0, nrows = 0, xllcorner = 0, yllcorner = 0, cellsize = 0;
 	std::map<std::string_view, size_t *> properties {
@@ -22,11 +23,12 @@ TerrainMesh::TerrainMesh(const std::filesystem::path & input)
 	}
 	std::vector<VertexHandle> vertices;
 	vertices.reserve(ncols * nrows);
+	TerrainMesh mesh;
 	for (size_t row = 0; row < nrows; ++row) {
 		for (size_t col = 0; col < ncols; ++col) {
 			float height = 0;
 			f >> height;
-			vertices.push_back(add_vertex({xllcorner + (col * cellsize), yllcorner + (row * cellsize), height}));
+			vertices.push_back(mesh.add_vertex({xllcorner + (col * cellsize), yllcorner + (row * cellsize), height}));
 		}
 	}
 	if (!f.good()) {
@@ -34,20 +36,22 @@ TerrainMesh::TerrainMesh(const std::filesystem::path & input)
 	}
 	for (size_t row = 1; row < nrows; ++row) {
 		for (size_t col = 1; col < ncols; ++col) {
-			add_face({
+			mesh.add_face({
 					vertices[ncols * (row - 1) + (col - 1)],
 					vertices[ncols * (row - 0) + (col - 0)],
 					vertices[ncols * (row - 0) + (col - 1)],
 			});
-			add_face({
+			mesh.add_face({
 					vertices[ncols * (row - 1) + (col - 1)],
 					vertices[ncols * (row - 1) + (col - 0)],
 					vertices[ncols * (row - 0) + (col - 0)],
 			});
 		}
 	}
-	update_face_normals();
-	update_vertex_normals();
+	mesh.update_face_normals();
+	mesh.update_vertex_normals();
+
+	return mesh;
 };
 
 OpenMesh::FaceHandle
diff --git a/game/terrain2.h b/game/terrain2.h
index 5539a50..69cd380 100644
--- a/game/terrain2.h
+++ b/game/terrain2.h
@@ -18,8 +18,11 @@ struct TerrainTraits : public OpenMesh::DefaultTraits {
 };
 
 class TerrainMesh : public OpenMesh::TriMesh_ArrayKernelT<TerrainTraits> {
+private:
+	TerrainMesh() = default;
+
 public:
-	explicit TerrainMesh(const std::filesystem::path &);
+	static TerrainMesh loadFromAsciiGrid(const std::filesystem::path &);
 
 	struct PointFace {
 		// NOLINTNEXTLINE(hicpp-explicit-conversions)
diff --git a/test/test-terrain.cpp b/test/test-terrain.cpp
index 53eebfb..512a90e 100644
--- a/test/test-terrain.cpp
+++ b/test/test-terrain.cpp
@@ -8,7 +8,7 @@
 
 class TestTerrainMesh : public TerrainMesh {
 public:
-	TestTerrainMesh() : TerrainMesh {FIXTURESDIR "height/SD19.asc"} { }
+	TestTerrainMesh() : TerrainMesh {TerrainMesh::loadFromAsciiGrid(FIXTURESDIR "height/SD19.asc")} { }
 };
 
 constexpr size_t ncols = 200, nrows = 200, xllcorner = 310000, yllcorner = 490000, cellsize = 50;
-- 
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