pointcloud to trace to 3D space a poorman’s guide. (WIP)

First catch your data.

Wrestle it into the processing and editing software of your choice and process and clean your points to taste. When you are happy with this get it into cloud compare.

If you are using real world coordinates, now’s the time to make a copy of the global-shift used on opening to avoid headaches later (select a cloud, Edit -> global shift).

Dice into bite-size portions along the faces of interest (walls, ceilings, floors etc) using the slice tool.

The faffy bit.

This bit needs a bit of prep, and some notes to not get yourself in a mess.

Step 1. choose a piece

Step 2. move the view so you are looking toward the face. You don’t need to be precise.

Step 3. Use the point picking tool to make 2 points at either end of your wall roughly where you want a baseline to be.

Save these points as a text file.

Step 4: open text file in a text editor of your choice, and level the Z. E.g. if point 1 is Z 102.33 and point 2 is Z 103.65, change them both to 102.00.

Then, copy point 2 and paste on the next line and change the Z to something more, such as 107 in this example – this is point 3.

Step 5: open this file in cloud compare and delete the original points

Step 6: use the alignment tool to reposition these 3 points on the flat – you select point 1 (bottom left) first, then point 2, then point 3.

Step 7: copy the transform that is displayed in the console, select the original pointcloud and transform (cmd/ctrl + t) and paste to apply the same transform to the pointcloud

This has got the pointcloud belly up for rasterizing. Next we want to make it make it as QGIS friendly as possible.

I’d suggest doing up to step 7 for all of the walls you want first, as it’s easy to forget the next step later if you’re not careful.

Step 8: To be as grid friendly in our 2D work as we can, use the power of maths and the transform tool to set the y to the z of points 1 and 2. Look at the Y of your repositioned point with the point tool, it will be something a bit random, like 8.2. So in this example, subtract 8.2 from 102, and then transform the cloud and points accordingly. i.e. y= (102-8.2).

Step 9: save these new coordinates, along with the small y transform.

You could do something similar with the X if you want so that your length dimensions start at 0 from point 1, or something else so that all your walls line up nicely. As you like.

Step 10: The global shift again. We want it in local coordinates, cos it don’t make no sense otherwise. Select all your transformed walls, and set the global shift to 0.

Step 11: rasterize your walls.

Step 12: open in QGIS and draw!
Your Y is Z in the real world, your X is just metres from

If you add you XY points, and to QGIS, and label them up with the original coordinates, you now have a way to print your data in 2D with enough information to return it back into 3D should you only have a book to go on.