Make it possible to fade in/out RenderableFieldLinesSequences (e.g. magnetosphere)

modules/fieldlinessequence/rendering/renderablefieldlinessequence.cpp

@@ -354,6 +354,8 @@ RenderableFieldlinesSequence::RenderableFieldlinesSequence(
 {
     const Parameters p = codegen::bake<Parameters>(dictionary);
 
+    addProperty(Fadeable::_opacity);
+
     // Extracts the general information (from the asset file) that
     // is mandatory for the class to function;
     std::string fileTypeString;
@@ -1031,6 +1033,8 @@ void RenderableFieldlinesSequence::render(const RenderData& data, RendererTasks&
         global::windowDelegate->applicationTime() * (_flowReversed ? -1 : 1)
     );
 
+    _shaderProgram->setUniform("opacity", opacity());
+
     bool additiveBlending = false;
     if (_colorABlendEnabled) {
         additiveBlending = true;

modules/fieldlinessequence/shaders/fieldlinessequence_fs.glsl

@@ -28,7 +28,7 @@ in vec4 vs_color;
 in float vs_depth;
 
 uniform bool usingAdditiveBlending;
-
+uniform float opacity;
 
 Fragment getFragment() {
   if (vs_color.a == 0) {
@@ -40,6 +40,7 @@ Fragment getFragment() {
   Fragment frag;
   frag.depth = vs_depth;
   frag.color = fragColor;
+  frag.color.a *= opacity;
 
   // G-Buffer
   frag.gPosition  = vec4(0.0);//vs_gPosition;