Gridded2DSet for a irregular grid / geometry of points


hi.

i have a function (x,y) -> (color) and use it as a background for a diagramm. now i try to transform this background for a diagramm with logarithmic axisis. that means i need a grid with irregular distances. the gridded2dset i used had either the wrong length or the wrong dimension or was useless in an other way. i have no idea how to go on. please help! (may be with same code?)

an other question is the geometry of the points in visad. do they have to be squared or are there other forms. and is it possible to center the points on the coordinates? if i try to pick a point near many others it could help if the center of the point would be the best place for.

thanks for all.

sven