if i put two surface's it seems that therion writes both in the lox file. loch reads the first only. but it can flawlessly read and display both (just replace the if with a loop) ... although maybe they are treated as two sheets of "The Surface". that's fine and i can get nice dem with the cave and surfaces for geological planar features ... the bitmap is a bit of a problem though: only the first surface bitmap is used (ok: can comment on that test and get around it). the bitmap is applied to both sheets (=surface's). the bitmap "tiles" the surface, instead of being overlaid on it [not sure about this]. what i would like: - exporting two or more surfaces - marking one surface as "DEM" and clipping the others in Z to this, unless the option "-clip off" - loch attaching the bitmaps to their grids. replay to Alexander mail: - for the fonts you can edit xtherion init file and set your favourite fonts. the file is well commented. - for Xwindow error on loch, don't know: you may follow the instructions in the error message and debug the program, or provide the lox file that crashed it. marco