I want to create aspect-aware contours (also called illuminated contours or Tanaka contours) for a map I have created in QGIS but finishing in Illustrator.

To do this I need the colour or luminosity of the contour lines to change depending on their azimuth or angle from northwest like this (done manually):

enter image description here

Is there a way to do this? Ideally without exploding the line into individual 2-vertex segments.

  • Do you want each segment to have a solid color or could the whole thing be a smooth gradient? Is your map going to have straight lines only or is it going to have irregular / smooth shapes?
    – Luciano
    Aug 13, 2019 at 15:28
  • 1
    No, there is no such function
    – joojaa
    Aug 13, 2019 at 15:35
  • @Luciano A smooth gradient would be best, the map will have irregular / smooth shaped contours. Aug 13, 2019 at 15:42
  • @joojaa well that's unfortunate. Aug 13, 2019 at 15:42
  • If it wouldnt have been a question of maps i would have suggested it could be scripted but with maps you most likely have extremely many elements so this would most likely kill your computer.
    – joojaa
    Aug 13, 2019 at 15:53

1 Answer 1


Illustrator contains no inherent method of reading the angle of an object and then applying appearance attributes (fill/stroke) to that object based upon its angle.

In other words, no you can't apply a fill or stroke based solely upon the angle of an object.

  • Well that sucks but thanks for the answer. I'll have to do that in GIS before importing into Illustrator, maybe as individual segments as long as it doesn't set my computer on fire. Aug 14, 2019 at 8:06

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