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