ported from perforce

DonkeysAndDroids.Godot/HexMeshBuilder.cs

@@ -0,0 +1,75 @@
+using System;
+using Godot;
+using Array = Godot.Collections.Array;
+
+public static class HexMeshBuilder
+{
+    public static ArrayMesh CreateFlatHexMesh()
+    {
+        var uvs = new Vector2[19];
+        var vertices = new Vector3[19];
+        var normals = new Vector3[19];
+
+        const float height = 0.02f;
+        vertices[0] = new(0f, height, 0f);
+        uvs[0] = new(0.5f, 0.5f);
+        normals[0] = Vector3.Up;
+
+        for (var i = 0; i < 18; i++)
+        {
+            var angleDeg = 60f * i - 30f;
+            var angleRad = Mathf.DegToRad(angleDeg);
+            var x = MathF.Cos(angleRad);
+            var z = MathF.Sin(angleRad);
+
+            var y = i >= 12 ? height : 0.0f;
+            var s = 1.0f - y;
+            vertices[i + 1] = new(x * s, y, z * s);
+            uvs[i + 1] = 
+                i < 6 ? new((i % 6), 0.5f) : 
+                i >= 12 ? new Vector2(x * 0.5f + 0.5f, z * 0.5f + 0.5f) :
+                new((i % 6), 0.5f + height);
+            normals[i + 1] = 
+                i < 6 ? Vector3.Up : 
+                i >= 12 ? new Vector3(x, s, z).Normalized() :
+                new Vector3(x, 0.75f, z).Normalized();
+        }
+
+        var indices = new int[18 * 3];
+        var idx = 0;
+        for (var i = 0; i < 6; i++)
+        {
+            var curr = i + 1;
+            var next = (i + 1) % 6 + 1;
+
+            indices[idx++] = 0;
+            indices[idx++] = curr + 12;
+            indices[idx++] = next + 12;
+        }
+
+        for (var j = 0; j < 6; j++)
+        {
+            var curr = j + 7;
+            var next = (j + 1) % 6 + 7;
+
+            indices[idx++] = curr;
+            indices[idx++] = next;
+            indices[idx++] = next + 6;
+            indices[idx++] = curr;
+            indices[idx++] = next + 6;
+            indices[idx++] = curr + 6;
+        }
+
+        var arrays = new Array();
+        arrays.Resize((int)Mesh.ArrayType.Max);
+        arrays[(int)Mesh.ArrayType.Vertex] = vertices;
+        arrays[(int)Mesh.ArrayType.Normal] = normals;
+        arrays[(int)Mesh.ArrayType.Index] = indices;
+        arrays[(int)Mesh.ArrayType.TexUV] = uvs;
+
+        var mesh = new ArrayMesh();
+        mesh.AddSurfaceFromArrays(Mesh.PrimitiveType.Triangles, arrays);
+
+        return mesh;
+    }
+}