From 6245f795e9c4546cf4ef86b27bc764cc9a896195 Mon Sep 17 00:00:00 2001
From: Kae <80987908+Novaenia@users.noreply.github.com>
Date: Sat, 31 May 2025 16:35:10 +1000
Subject: simple support for animated parallax textures

---
 source/game/StarAnimation.cpp               | 4 ++--
 source/game/StarParallax.cpp                | 9 +++++++++
 source/game/StarParallax.hpp                | 3 +++
 source/rendering/StarEnvironmentPainter.cpp | 9 +++++++++
 4 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/source/game/StarAnimation.cpp b/source/game/StarAnimation.cpp
index 09da400..d8d62dc 100644
--- a/source/game/StarAnimation.cpp
+++ b/source/game/StarAnimation.cpp
@@ -27,8 +27,8 @@ Animation::Animation(Json config, String const& directory) {
   // to the end.
   m_appendFrame = !m_base.contains("<index>");
   m_frameNumber = config.getInt("frameNumber", 1);
-  m_animationCycle = config.getDouble("animationCycle", 1.0);
-  m_animationTime = m_animationCycle * config.getDouble("loops", 1.0);
+  m_animationCycle = config.getFloat("animationCycle", 1.0);
+  m_animationTime = m_animationCycle * config.getFloat("loops", 1.0);
   m_angle = config.getFloat("angle", 0.0f);
   m_offset = jsonToVec2F(config.get("offset", JsonArray{0.0f, 0.0f}));
   m_centered = config.getBool("centered", true);
diff --git a/source/game/StarParallax.cpp b/source/game/StarParallax.cpp
index d537b2c..c6bc044 100644
--- a/source/game/StarParallax.cpp
+++ b/source/game/StarParallax.cpp
@@ -18,12 +18,18 @@ ParallaxLayer::ParallaxLayer() {
   lightMapped = false;
   fadePercent = 0;
   directives = "";
+  frameNumber = 1;
+  frameOffset = 0;
+  animationCycle = 1.0f;
   alpha = 1.0f;
 }
 
 ParallaxLayer::ParallaxLayer(Json const& store) : ParallaxLayer() {
   textures = jsonToStringList(store.get("textures"));
   directives = store.getString("directives");
+  frameNumber = store.getInt("frameNumber", 1);
+  frameOffset = store.getInt("frameOffset", 0);
+  animationCycle = store.getFloat("animationCycle", 1.0f);
   parallaxValue = jsonToVec2F(store.get("parallaxValue"));
   repeat = jsonToVec2B(store.get("repeat"));
   tileLimitTop = store.optFloat("tileLimitTop");
@@ -42,6 +48,9 @@ Json ParallaxLayer::store() const {
   return JsonObject{
       {"textures", jsonFromStringList(textures)},
       {"directives", directives.string()},
+      {"frameNumber", frameNumber},
+      {"frameOffset", frameOffset},
+      {"animationCycle", animationCycle},
       {"parallaxValue", jsonFromVec2F(parallaxValue)},
       {"repeat", jsonFromVec2B(repeat)},
       {"tileLimitTop", jsonFromMaybe(tileLimitTop)},
diff --git a/source/game/StarParallax.hpp b/source/game/StarParallax.hpp
index ee65955..5f6b8d0 100644
--- a/source/game/StarParallax.hpp
+++ b/source/game/StarParallax.hpp
@@ -21,6 +21,9 @@ struct ParallaxLayer {
 
   List<String> textures;
   Directives directives;
+  unsigned frameNumber;
+  int frameOffset;
+  float animationCycle;
   float alpha;
   Vec2F parallaxValue;
   Vec2B repeat;
diff --git a/source/rendering/StarEnvironmentPainter.cpp b/source/rendering/StarEnvironmentPainter.cpp
index d95d968..197914e 100644
--- a/source/rendering/StarEnvironmentPainter.cpp
+++ b/source/rendering/StarEnvironmentPainter.cpp
@@ -251,6 +251,8 @@ void EnvironmentPainter::renderParallaxLayers(
 
     AssetPath first = layer.textures.first();
     first.directives += layer.directives;
+    if (layer.frameNumber > 1)
+      first.subPath.emplace("0");
     Vec2F parallaxSize = Vec2F(m_textureGroup->loadTexture(first)->size());
     Vec2F parallaxPixels = parallaxSize * camera.pixelRatio();
 
@@ -320,6 +322,13 @@ void EnvironmentPainter::renderParallaxLayers(
         for (auto const& textureImage : layer.textures) {
           AssetPath withDirectives = textureImage;
           withDirectives.directives += layer.directives;
+          if (layer.frameNumber > 1) {
+            float time_within_cycle = (float)fmod(sky.epochTime, (double)layer.animationCycle);
+            float time_per_frame = layer.animationCycle / layer.frameNumber;
+            float frame_number = time_within_cycle / time_per_frame;
+            int frame = (layer.frameOffset + clamp<int>(frame_number, 0, layer.frameNumber - 1)) % layer.frameNumber;
+            withDirectives.subPath.emplace(toString(frame));
+          }
           if (auto texture = m_textureGroup->tryTexture(withDirectives)) {
             RectF drawRect = RectF::withSize(anchorPoint, subImage.size() * camera.pixelRatio());
             primitives.emplace_back(std::in_place_type_t<RenderQuad>(), std::move(texture),
-- 
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