Added covers, cross-fade

src/items/InteractiveObject.cpp

@@ -63,6 +63,23 @@ namespace ZL {
         isAnimating = true;
     }
 
+    void InteractiveObject::fadeTo(float targetAlpha, float durationSec, std::function<void()> onComplete) {
+        if (isAnimating) return;
+        AnimTask task;
+        task.type        = AnimTask::Type::Fade;
+        task.startPos    = position;
+        task.startRotY   = rotationY;
+        task.startScale  = alpha;         // reuse startScale to hold start alpha
+        task.targetPos   = position;
+        task.targetRotY  = rotationY;
+        task.targetScale = targetAlpha;   // reuse targetScale to hold target alpha
+        task.durationMs  = durationSec * 1000.f;
+        task.elapsedMs   = 0.f;
+        task.onComplete  = std::move(onComplete);
+        animTask    = std::move(task);
+        isAnimating = true;
+    }
+
     void InteractiveObject::update(int64_t deltaMs) {
         if (!isAnimating || !animTask) return;
 
@@ -81,6 +98,9 @@ namespace ZL {
             case AnimTask::Type::Scale:
                 scale = task.startScale + (task.targetScale - task.startScale) * t;
                 break;
+            case AnimTask::Type::Fade:
+                alpha = task.startScale + (task.targetScale - task.startScale) * t;
+                break;
         }
 
         if (t >= 1.0f) {
@@ -99,6 +119,12 @@ namespace ZL {
 
     void InteractiveObject::draw(Renderer& renderer) const {
         if (!isActive || !loadedObject.texture) return;
+
+        if (alpha < 0.999f) {
+            glEnable(GL_BLEND);
+            glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+        }
+
         renderer.PushMatrix();
         renderer.TranslateMatrix(position);
         if (rotationY != 0.f) {
@@ -109,9 +135,13 @@ namespace ZL {
         if (scale != 1.f)
             renderer.ScaleMatrix(scale);
         renderer.RenderUniform1i(textureUniformName, 0);
+        renderer.RenderUniform1f("uAlpha", alpha);
         glBindTexture(GL_TEXTURE_2D, loadedObject.texture->getTexID());
         renderer.DrawVertexRenderStruct(loadedObject.mesh);
         renderer.PopMatrix();
+
+        // Restore uAlpha so subsequent fog-shader users (character weapons, etc.) are not affected.
+        renderer.RenderUniform1f("uAlpha", 1.0f);
     }
 
 } // namespace ZL