I need to paint on only one side(spotlight) of the petal. i have modeled it in maya and then modified in zbrush using a plane.
If the petals are one polygon thick, it’s impossible.
If the petals have a front and a back surface, it would normally be possible using Backface Masking (found in the Brush palette). Unfortunately, this feature is currently not working correctly and is being investigated by the development team.
A solution would be if you could apply different groups to the front and back surfaces. You could then hide or mask one surface so that you can paint the other.