Hi @jtpausti ,

>>>>>to smooth out that polyline between the white and gradient regions

What do you mean?

Do you want to make it thinner?

You can remove this polylines from the drawing, or if you need them, you can use another method to rasterize the drawing:

Print it to PDF with AutoCAD PDF (High Quality Print).pc3 printer, then open resulting PDF in Preview.app and save as raster image (JPG, PNG, TIFF)