unity popcornfx ue4 editor unity3d mesh script shape-sampler unreal attribute plugin rendering particle unreal-4 spawn crash meshsampling collision animation position import pk-unityplugin baking error effects unreal-engine-4 hh-unityplugin ribbon android curve events fbx rotation bug vr billboarding ios shader camera image spawner axis fx compile-error sampler-shape projection physics material issues event sampler velocity build time spatial-layers unreal-collision distortion dll animtrack blueprint lighting attractor builder delay flux api scale scaling parent-field shape attributes atlas id texture evolver model backdrop folder runtime popcorn projector evolverspawner draw-order plexus - cull time-multiplier dllnotfoundexeption htm folder-structure audiospectrum ui sound cparticlesampleranimtrack preferences linux bake order track pivot