CloudCompare forum

I open an e57 file (~250Mb), apply an affine transform, then save as an e57 file. The file size increases by ~50% and reports the same number of points when loaded but displays at a fraction of the point density (looks subsampled/decimated). Any ideas about what is happening? The affine transform 'georeferences' the file and the coordinates become large numbers (in this case State Plane values). This might be the cause of the increase in file size...but is it also causing the display issue?

Indeed, we use 32 bits float precision internally, so very big coordinates can cause a major precision loss (therefore all the points appear to be 'aligned' on a grid).

We should try to warn the user about this. Meanwhile, to cope with that you should only apply the rotation part of your transformation with the 'Edit > Transformation' tool. Then set the remaining translation as 'Global shift' (with "Edit > Edit global shift"). Warning: you'll have to input the opposite translation vector here as when CC will save your file all the points will be translated of (-Tx,-Ty,-Tz).

Thank you for that. I observed upon closer examination the 'stacking' of my points on a grid that looked like all Y data was at 10cm intervals. I now know how do deal with it and thank you for the clarification.