animations

interfaces/Crafter.Graphics-Animation.cppm

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+/*
+Crafter®.Graphics
+Copyright (C) 2025 Catcrafts®
+Catcrafts.net
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 3.0 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
+*/
+
+export module Crafter.Graphics:Animation;
+import std;
+
+namespace Crafter {
+    template <typename T>
+    constexpr T Lerp(T a, T b, double elapsed) {
+        return a + static_cast<T>(elapsed * (b - a));
+    }
+
+    template <typename Tuple, std::size_t... Is>
+    constexpr auto LerpTupleImpl(const Tuple& a, const Tuple& b, double elapsed, std::index_sequence<Is...>) {
+        return std::make_tuple(Lerp(std::get<Is>(a), std::get<Is>(b), elapsed)...);
+    }
+
+    template <typename Tuple>
+    constexpr auto LerpTuple(const Tuple& a, const Tuple& b, double elapsed) {
+        return LerpTupleImpl(a, b, elapsed, std::make_index_sequence<std::tuple_size_v<Tuple>>{});
+    }
+
+    export template <typename T>
+    struct Keyframe{
+        std::chrono::duration<double> duration;
+        T values;
+    };
+
+    export template <typename T>
+    struct Animation {
+        std::vector<Keyframe<T>> keyframes;
+        std::uint_fast32_t currentFrame;
+        std::chrono::time_point<std::chrono::high_resolution_clock> startedAt;
+        Animation(std::vector<Keyframe<T>>&& keyframes) : keyframes(std::move(keyframes)) {}
+        void Start(std::chrono::time_point<std::chrono::high_resolution_clock> time) {
+            currentFrame = 0;
+            startedAt = time;
+        }
+        T Play(std::chrono::time_point<std::chrono::high_resolution_clock> time) {
+            std::chrono::duration<double> elapsed = time - startedAt;  // elapsed time since animation started
+            std::chrono::duration<double> accumulated(0);
+
+            for (std::uint_fast32_t i = currentFrame; i < keyframes.size() - 1; ++i) {
+                accumulated += keyframes[i+1].duration;
+                if (elapsed < accumulated) {
+                    std::chrono::duration<double> frameStartTime = accumulated - keyframes[i+1].duration;
+                    auto t = (elapsed - frameStartTime) / keyframes[i+1].duration.count();
+
+                    currentFrame = i;
+                    return LerpTuple(
+                        keyframes[i].values,
+                        keyframes[i + 1].values,
+                        t.count()
+                    );
+                }
+            }
+
+            // If we get here, we're past the last keyframe
+            currentFrame = keyframes.size() - 1;
+            return keyframes.back().values;
+        }
+    };
+}