4 files changed, 18 insertions, 3 deletions

@@ -414,6 +414,15 @@ function SetAnimationSlowdown(spriteName, amount)
   sprite.animSlowdown = amount
 end
 
+--- Sets the opacity of the sprite when it is rendered.
+-- @param spriteName the alias of the sprite to modify
+-- @param amount a value from 0.0 to 1.0
+function SetOpacity(spriteName, amount)
+  local spriteId = getSpriteByAlias(spriteName)
+  local sprite = getSprite(spriteId)
+  sprite.opacity = amount
+end
+
 --- Sets the enclosure zone for a sprite.
 -- The sprite will be prevented from exiting the area defined by that zone.
 function AddEnclosureZone(spriteName, zone)
@@ -112,7 +112,9 @@ void Renderer::renderSprite(const Sprite& sprite) {
     if (sprite.hasShadow) {
       int shadowTexId = loadImageFromFile("../res/shadow.png");
       const SDL_Rect shadowDest { sprite.loc.x() - 8, sprite.loc.y() - 8, 16, 8 };
-      SDL_RenderCopy(ren_.get(), textures_.at(shadowTexId).get(), nullptr, &shadowDest);
+      SDL_Texture* shadowTex = textures_.at(shadowTexId).get();
+      SDL_SetTextureAlphaMod(shadowTex, sprite.opacity * 255);
+      SDL_RenderCopy(ren_.get(), shadowTex, nullptr, &shadowDest);
     }
 
     const SpriteFrame& frame = sprite.frames.at(sprite.animations.at(sprite.animationId).frameIndices.at(sprite.animationFrame));
@@ -121,7 +123,9 @@ void Renderer::renderSprite(const Sprite& sprite) {
     if (sprite.bobbing) {
       dest.y -= sprite.bobAmount;
     }
-    SDL_RenderCopy(ren_.get(), textures_.at(loadImageFromFile(sprite.spritesheet)).get(), &src, &dest);
+    SDL_Texture* textureToRender = textures_.at(loadImageFromFile(sprite.spritesheet)).get();
+    SDL_SetTextureAlphaMod(textureToRender, sprite.opacity * 255);
+    SDL_RenderCopy(ren_.get(), textureToRender, &src, &dest);
   }
 }
 
@@ -55,7 +55,8 @@ ScriptSystem::ScriptSystem(Game& game) : game_(game) {
     "solid", &Sprite::solid,
     "behaviourType", &Sprite::behaviourType,
     "followSpriteId", &Sprite::followSpriteId,
-    "interactionScript", &Sprite::interactionScript);
+    "interactionScript", &Sprite::interactionScript,
+    "opacity", &Sprite::opacity);
 
   engine_.new_usertype<MessageSystem>(
     "message",
@@ -100,6 +100,7 @@ public:
   int bobAmount = 0;
   bool bobbingDown = false;
   int animSlowdownProgress = 0;
+  double opacity = 1.0;
 
   // Animation (controls)
   bool normallyHasShadow = false;