Perlin bias for layerRGBA

Perlin Bias can add contrast for vertex coloring
MRIcroS('closeAllItems')
MRIcroS('addLayer','stroke.trib')
MRIcroS('addTrack','stroke.trk',1,9)
MRIcroS('clipMesh',1,[-inf -inf -inf], [inf inf 30])
MRIcroS('layerRGBA', 1, 0.9, 0, 0, 1, 0.35)