topic Digitising elevations from point cloud. in AutoCAD Forum

Digitising elevations from point cloud.

dlbsurveysuk — Tue, 14 Apr 2020 07:13:01 GMT

Hi, point cloud newbie here.

I have some 3d survey data of a small house and back yard in autocad to which I have attached a point cloud using surveyed targets (specified x,y,z co-ordinates of surveyed targets in Recap Pro).

I would like to extract some 2d elevations of the house to digitise/trace over (the y values of the elevations must conform to the z values of the 3d model).

I'm basically making it up as I go along by watching random videos on Youtube etc without really knowing what I'm doing. I am now stuck. This should be a simple procedure?!!?!

I've rotated the house about the z axis using 3drotate to get square to the building and have been trying to use a section/elevation plane/slice and the generate section/elevation dialogue to create a 2d section/elevation and get the error "there are no solids or surfaces that can be projected".

I don't know if it's the way I'm using the section plane or I'm just going about the whole thing in the wrong way. Have wasted many hours trying to sort this out.

Latest video watched https://www.youtube.com/watch?v=fC6WwoaqusI&t=313s

Tried to follow the method in the above video but got the above error, plus my Autocad doesn't even show the same dialogues.

Any help or general pointers to clear information on how to achieve this would be much appreciated.

Thanks.

Re: Digitising elevations from point cloud.

Pointdump — Tue, 14 Apr 2020 08:03:16 GMT

Quentin,
Welcome to the Autodesk Forums.
"...my Autocad doesn't even show the same dialogues."
Video is using AutoCAD MEP. Are you using Vanilla AutoCAD or a "Vertical", like Civil 3D?
Please elaborate a little about your goal. Do you need a Surface to design a driveway, or a plan view to design a room addition, or maybe something else?

Dave

Re: Digitising elevations from point cloud.

dlbsurveysuk — Tue, 14 Apr 2020 08:20:14 GMT

Hi, thanks for the reply.

I am using Vanilla Autocad 2021.

The goal is to extract 2d plans - A topographical plan and three elevations (front, back, and side). Internal plans are on hold at the moment due to the coronavirus situation.

The drawings are for an Architect to design a room extension.

Quentin.

Re: Digitising elevations from point cloud.

Pointdump — Tue, 14 Apr 2020 14:12:40 GMT

Quentin,
I would have thought, like you, that plane slice would have been just the ticket for drawing a building footprint. But then, I've never done that with a point cloud, so maybe there's a trick or two to make it happen. Maybe someone here has done this very thing and will weigh in with key insights.
Dave

Re: Digitising elevations from point cloud.

dlbsurveysuk — Tue, 14 Apr 2020 19:07:50 GMT

OK I've figured it out.

1. Turn off Dynamic UCS (f6)

2. Rotate point cloud in the xy plane to make required elevation square to the x axis

3 Introduce a section plane just in front of the line of the elevation

4 Rotate the UCS 90 degrees about the x axis so the z becomes y for 2d drafting

5 Turn off 3d snaps

6 Trace over point cloud

This gives me a plan of any elevation I want at the correct level.