precompute texcoords

2 files changed, 36 insertions, 14 deletions

diff --git a/src/tile-atlas.cpp b/src/tile-atlas.cpp
index 50f28cd0..0b09b493 100644
--- a/src/tile-atlas.cpp
+++ b/src/tile-atlas.cpp
@@ -8,12 +8,11 @@
 namespace floormat {
 
 tile_atlas::tile_atlas(Containers::StringView name, const ImageView2D& image, Vector2ui dims) :
-    name_{name},
-    size_{image.size()},
-    dims_{dims}
+    texcoords_{make_texcoords_array(Vector2ui(image.size()), dims)},
+    name_{name}, size_{image.size()}, dims_{dims}
 {
     CORRADE_INTERNAL_ASSERT(dims_[0] > 0 && dims_[1] > 0);
-    CORRADE_INTERNAL_ASSERT(size_ % dims_ == Vector2ui{});
+    CORRADE_INTERNAL_ASSERT(size_ % dims_ == Vector2ui());
     CORRADE_INTERNAL_ASSERT(dims_.product() < 256);
     tex_.setWrapping(GL::SamplerWrapping::ClampToEdge)
         .setMagnificationFilter(GL::SamplerFilter::Linear)
@@ -24,19 +23,36 @@ tile_atlas::tile_atlas(Containers::StringView name, const ImageView2D& image, Ve
         .setSubImage(0, {}, image);
 }
 
-std::array<Vector2, 4> tile_atlas::texcoords_for_id(std::size_t id_) const
+std::array<Vector2, 4> tile_atlas::texcoords_for_id(std::size_t i) const
 {
-    const auto sz = size_/dims_;
-    ASSERT(id_ < sz.product());
-    const Vector2ui id = { (UnsignedInt)id_ % dims_[0], (UnsignedInt)id_ / dims_[0] };
+    ASSERT(i < (size_/dims_).product());
+    return texcoords_[i];
+}
+
+auto tile_atlas::make_texcoords(Vector2ui size, Vector2ui dims, std::uint_fast16_t i) -> texcoords
+{
+    const auto sz = size/dims;
+    const Vector2ui id = { (UnsignedInt)i % dims[0], (UnsignedInt)i / dims[0] };
     const Vector2 p0(id * sz), p1(sz);
     const auto x0 = p0.x(), x1 = p1.x()-1, y0 = p0.y(), y1 = p1.y()-1;
     return {{
-        { (x0+x1)/size_[0], (y0+y1)/size_[1]  }, // bottom right
-        { (x0+x1)/size_[0], y0/size_[1]       }, // top right
-        { x0/size_[0],      (y0+y1)/size_[1]  }, // bottom left
-        { x0/size_[0],      y0/size_[1]       }  // top left
+        { (x0+x1)/size[0], (y0+y1)/size[1]  }, // bottom right
+        { (x0+x1)/size[0], y0     /size[1]  }, // top right
+        { x0     /size[0], (y0+y1)/size[1]  }, // bottom left
+        { x0     /size[0], y0     /size[1]  }  // top left
     }};
 }
 
+auto tile_atlas::make_texcoords_array(Vector2ui size, Vector2ui dims) -> std::unique_ptr<const texcoords[]>
+{
+    const auto sz = size/dims;
+    const std::uint32_t max = sz.product();
+    auto ptr = std::make_unique<std::array<Vector2, 4>[]>(max);
+    for (std::uint_fast16_t i = 0; i < max; i++)
+    {
+        ptr[i] = make_texcoords(size, dims, i);
+    }
+    return ptr;
+}
+
 } // namespace floormat
diff --git a/src/tile-atlas.hpp b/src/tile-atlas.hpp
index 08a090a4..5fb0f899 100644
--- a/src/tile-atlas.hpp
+++ b/src/tile-atlas.hpp
@@ -3,6 +3,7 @@
 #include <Magnum/GL/Texture.h>
 #include <array>
 #include <string>
+#include <memory>
 
 namespace std::filesystem { class path; }
 
@@ -11,20 +12,25 @@ namespace floormat {
 struct tile_atlas final
 {
     using quad = std::array<Vector3, 4>;
+    using texcoords = std::array<Vector2, 4>;
 
     tile_atlas(Containers::StringView name, const ImageView2D& img, Vector2ui dimensions);
 
-    std::array<Vector2, 4> texcoords_for_id(std::size_t id) const;
+    texcoords 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_; }
+    [[maybe_unused]] Vector2ui pixel_size() const { return size_; }
     Vector2ui num_tiles() const { return dims_; }
     GL::Texture2D& texture() { return tex_; }
     Containers::StringView name() const { return name_; }
 
 private:
+    static std::unique_ptr<const texcoords[]> make_texcoords_array(Vector2ui size, Vector2ui dims);
+    static texcoords make_texcoords(Vector2ui size, Vector2ui dims, std::uint_fast16_t i);
+
+    std::unique_ptr<const texcoords[]> texcoords_;
     GL::Texture2D tex_;
     std::string name_;
     Vector2ui size_, dims_;