It is possible to get the exact position on each triangle.
If I put an UVW MAP-modifier on the triangle, the left-bottom-corner of the plane-gizmo is the pivot-point of the distribution image.
But in UV-mode the map channel-option is greyed-out (map instead of image) and the 'match-color ID on map' doesn't seem to work anymore on a map channel different from 1.
Do you know it it is possible to work with 2 map channels in UV-mode? (1 for distribution, 1 for match color ID)
It works for a mesh with 1 face, but not for RC or a mesh containing multiple faces.