Problem on save as after applying Z scale and Z translation

[Olivier.Eckmann]

Hi,

I begin with cloudcompare, so I'm missing something, but I don't find where.
I've a E57 pointcloud on which i should to apply a Z scale of 1.00535 followed by a Z translation of +0.10m.
It's OK on coordinates after these 2 transformations, by when I save to a new E57, coordinates are modified. XY are OK, but Z not.
I join a screencast of my workflow : https://autode.sk/3mbbiDp
If somebody can tell me where I'm wrong, I'll appreciate.

Thanks.

Olivier

[daniel]

I think the issue is that you should not leave the 'keep entity in place' option fixed when you apply the scale.

It will make the bounding-box center fixed in space (thus it will implicitly translate the cloud).

[Olivier.Eckmann]

Hi,

Box dimensions in Z is 35.078. Global box center has zvalue = 73.7539
If I :
Check "keep entity in place", scale is applied around 73.7539 => I should apply +0.10m in Z after
Uncheck "keep entity in place", scale is applied from 0, so I need to translate in Z of -0.38m.

In the 2 cases, values are correct and identical on transformed pointcloud when I check these values, but when I want to export this transformed pointcloud with a new E57 and reopen in CC, Z values are modified.

Olivier

[daniel]

Ah ok I understand your problem.

Are you applying the same Global Shift at loading time? Because if it's not the same run of CC, then the first point is used, and it won't have the same coordinates due to the scaling (hence, resulting in a different local coordinate system). Is it the case?