1 files changed, 74 insertions, 0 deletions
diff --git a/src/tile-atlas.hpp b/src/tile-atlas.hpp
new file mode 100644
index 00000000..b32a70d8
--- /dev/null
+++ b/src/tile-atlas.hpp
@@ -0,0 +1,74 @@
+#pragma once
+#include "compat/assert.hpp"
+#include <Magnum/Magnum.h>
+#include <Magnum/GL/RectangleTexture.h>
+#include <array>
+#include <string>
+
+namespace Magnum::Examples {
+
+struct tile_atlas final
+{
+    using quad = std::array<Vector3, 4>;
+
+    tile_atlas(Containers::StringView name, const ImageView2D& img, Vector2ui dimensions);
+
+    std::array<Vector2, 4> texcoords_for_id(std::size_t id) const;
+    static constexpr quad floor_quad(Vector3 center, Vector2 size);
+    static constexpr quad wall_quad_N(Vector3 center, Vector3 size);
+    static constexpr quad wall_quad_W(Vector3 center, Vector3 size);
+    static constexpr std::array<UnsignedShort, 6> indices(std::size_t N);
+    Vector2ui pixel_size() const { return size_; }
+    Vector2ui num_tiles() const { return dims_; }
+    GL::RectangleTexture& texture() { return tex_; }
+    Containers::StringView name() const { return name_; }
+
+private:
+    GL::RectangleTexture tex_;
+    std::string name_;
+    Vector2ui size_, dims_;
+};
+
+constexpr std::array<UnsignedShort, 6> tile_atlas::indices(std::size_t N)
+{
+    using u16 = UnsignedShort;
+    return {                                        /* 3--1  1 */
+        (u16)(0+N*4), (u16)(1+N*4), (u16)(2+N*4),   /* | /  /| */
+        (u16)(2+N*4), (u16)(1+N*4), (u16)(3+N*4),   /* |/  / | */
+    };                                              /* 2  2--0 */
+}
+
+constexpr tile_atlas::quad tile_atlas::floor_quad(const Vector3 center, const Vector2 size)
+{
+    float x = size[0]*.5f, y = size[1]*.5f;
+    return {{
+        { x + center[0], -y + center[1], center[2]},
+        { x + center[0],  y + center[1], center[2]},
+        {-x + center[0], -y + center[1], center[2]},
+        {-x + center[0],  y + center[1], center[2]},
+    }};
+}
+
+constexpr tile_atlas::quad tile_atlas::wall_quad_W(const Vector3 center, const Vector3 size)
+{
+    float x = size[0]*.5f, y = size[1]*.5f, z = size[2];
+    return {{
+        {-x + center[0],  y + center[1],     center[2] },
+        {-x + center[0],  y + center[1], z + center[2] },
+        {-x + center[0], -y + center[1],     center[2] },
+        {-x + center[0], -y + center[1], z + center[2] },
+    }};
+}
+
+constexpr tile_atlas::quad tile_atlas::wall_quad_N(const Vector3 center, const Vector3 size)
+{
+    float x = size[0]*.5f, y = size[1]*.5f, z = size[2];
+    return {{
+        { x + center[0], -y + center[1],     center[2] },
+        { x + center[0], -y + center[1], z + center[2] },
+        {-x + center[0], -y + center[1],     center[2] },
+        {-x + center[0], -y + center[1], z + center[2] },
+    }};
+}
+
+} // namespace Magnum::Examples