Wonderful. Just wondering, how many hours per week must they waste for a form of art that's just waiting for a pedestrian or a car to cross over and mar the whole pic...? Must feel terrible when it happens...
Thank you! 
well, it depends on the size or complexity of the image. It takes hours and days. Yeah, you are right,eventhough they try to cover it with plastic or a trauplin, the painting fades away eventually cos of weather, wind, pedestrians... And it's total disaster for them if it starts to rain.

@ cornelia : here are a few works of 3D art.
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and they arent real, they are '2-dimensional'. They only appear 3-dimensional when seen from the right angle. they appear a total distortation and dont make any sense if seen from the wrong side.