Document upright world planes; mod documentation

tests/TileSurfaceRasterizerTests.cs

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+namespace Cthangover.Mods.TileRender.Tests
+{
+    using Cthangover.Core.Mods.Testing;
+    using Godot;
+    /// <summary>Chunk edges, world phase and diagonal blending must match the full reference texture byte-for-byte.</summary>
+    public class TileSurfaceRasterizerTests
+    {
+        [ModTest("surfaces/homogeneous_field_preserves_every_patch_byte")]
+        static void HomogeneousPatch(ModTestContext ctx)
+        {
+            var atlas = new byte[16 * 16 * 4];
+            for (var i = 0; i < atlas.Length; i++) atlas[i] = (byte)(i * 73 % 256);
+            foreach (var size in new[] { 8, 32 })
+            foreach (var diffuse in new[] { false, true })
+            {
+                var field = new TileSurfaceField { Width = 3, Height = 2, TileSize = size, PatchSize = 16,
+                    Materials = new int[6], Diffuse = new[] { diffuse, diffuse, diffuse, diffuse, diffuse, diffuse } };
+                var pixels = TileSurfaceRasterizer.Render(field, atlas, 16, new Rect2I(0, 0, 3, 2));
+                for (var y = 0; y < 2 * size; y++) for (var x = 0; x < 3 * size; x++) for (var c = 0; c < 4; c++)
+                    ModAssert.Equal(atlas[((y % 16) * 16 + x % 16) * 4 + c], pixels[(y * 3 * size + x) * 4 + c], "exact source sample including alpha");
+            }
+        }
+        [ModTest("surfaces/chunks_equal_monolithic_pixels")]
+        static void ChunksEqualMonolithicPixels(ModTestContext ctx)
+        {
+            var field = new TileSurfaceField { Width = 4, Height = 3, TileSize = 8, PatchSize = 16,
+                Materials = new[] { 0, 0, 1, 1, 0, -1, 1, 1, 1, 0, 0, 1 },
+                Diffuse = new[] { true, true, true, true, true, true, true, false, true, true, true, true } };
+            var atlas = new byte[32 * 16 * 4];
+            for (var y = 0; y < 16; y++) for (var x = 0; x < 32; x++)
+            { var i = (y * 32 + x) * 4; atlas[i] = (byte)(x * 7); atlas[i + 1] = (byte)(y * 15); atlas[i + 3] = 255; }
+            var full = TileSurfaceRasterizer.Render(field, atlas, 32, new Rect2I(0, 0, 4, 3));
+            for (var cy = 0; cy < 3; cy++) for (var cx = 0; cx < 4; cx++)
+            {
+                var part = TileSurfaceRasterizer.Render(field, atlas, 32, new Rect2I(cx, cy, 1, 1));
+                for (var y = 0; y < 8; y++) for (var x = 0; x < 8; x++) for (var c = 0; c < 4; c++)
+                    ModAssert.Equal(full[((cy * 8 + y) * 32 + cx * 8 + x) * 4 + c], part[(y * 8 + x) * 4 + c], "chunk including halo and global patch phase");
+            }
+        }
+    }
+}