Deviations in width of hallway

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GCFdesign
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Re: Deviations in width of hallway

Post by GCFdesign »

I do not believe for this exercise that this would adequately define the required location of the desired hallway clearance envelope.

VXGrid wrote: Mon Mar 28, 2022 12:29 pm
landmeterbeuckx wrote: Fri Mar 25, 2022 12:56 pm Hi,
I have a project where there is a hallway scanned but there is a tolerance of 1.83m between points on both sides of the hallway.

Plastering wasn't done up to standards so there are places where it is 1.82m and others 1.84m

How would i tackle this so i can color my pointcloud green where it is fine but red where it is over tolerance.
Mh you can try to achieve that with PointCab Origins:
Activate the delta tool and the PDF export when doing a section.
Generate the section on the left wall, extend the bounding box over the right wall, set the colours and bounding boxes accordingly, rinse and repeat for the other side.
In the PDF on the last page there is in addition a % of how many points are within the generated bins.


Guess it could look like this:
(In my case everything between [4,3; 4,38) is red and everthing between [4,38; 4,39) is green.
deltaOrigins.png

Personally I think I would use red and blue - not red and green ;)
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Re: Deviations in width of hallway

Post by VXGrid »

GCFdesign wrote: Mon Mar 28, 2022 5:39 pm I do not believe for this exercise that this would adequately define the required location of the desired hallway clearance envelope.

Can you elaborate please?
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Re: Deviations in width of hallway

Post by GCFdesign »

VXGrid

Your proposed workflow would likely return a result, likewise the opposing datum at any location would conclude in a result. However, my point is that technically either datums are not truly definable, but merely a response to the captured data, which in turn such data, however small has itself been compromised in terms of accuracy (the nature of the data we all have to deal with).
An idealised hallway centre or axis throughout the data is not known and yet again from design stage to as-built such a path centre would itself mean nothing.
Clearly the 1.83m width is the driving criteria to search fro, however, how such an envelope of idealised space is located throughout the dataset is key in performing such a search.
It could be that your suggestion and indeed other suggestions would suffice, however, from a purest point of view, it would not, however, maybe your suggestion is as close to a practical solution that can be achieved.

VXGrid wrote: Tue Mar 29, 2022 7:22 am
GCFdesign wrote: Mon Mar 28, 2022 5:39 pm I do not believe for this exercise that this would adequately define the required location of the desired hallway clearance envelope.

Can you elaborate please?
Regards,

Gary Fellows

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GCF Design Limited

https://gcfdesign.wixsite.com/gcfdesign
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Re: Deviations in width of hallway

Post by smacl »

GCFdesign wrote: Tue Mar 29, 2022 7:47 am VXGrid

Your proposed workflow would likely return a result, likewise the opposing datum at any location would conclude in a result. However, my point is that technically either datums are not truly definable, but merely a response to the captured data, which in turn such data, however small has itself been compromised in terms of accuracy (the nature of the data we all have to deal with).
An idealised hallway centre or axis throughout the data is not known and yet again from design stage to as-built such a path centre would itself mean nothing.
Clearly the 1.83m width is the driving criteria to search fro, however, how such an envelope of idealised space is located throughout the dataset is key in performing such a search.
It could be that your suggestion and indeed other suggestions would suffice, however, from a purest point of view, it would not, however, maybe your suggestion is as close to a practical solution that can be achieved.

VXGrid wrote: Tue Mar 29, 2022 7:22 am
GCFdesign wrote: Mon Mar 28, 2022 5:39 pm I do not believe for this exercise that this would adequately define the required location of the desired hallway clearance envelope.

Can you elaborate please?
Agreed, assuming the walls should be vertical one approach would be as follows;
  • Draw a rough centre polyline down the corridor and extrude this vertically to form a set of planes / polyplane
  • Create a grid at regular horizontal and vertical intervals along the above
  • Project points left and right from each grid position intersecting the point cloud to determine the width
  • Use these widths and intersection positions for the final analysis
We do something similar in tunnelling for clearance analysis, where we move a section template along an alignment at regular intervals, fit the position of the template in section against the cloud at each interval and use the result as the new centre line for our extruded model. In tunnelling this is called a wriggle survey and can also be applied to the likes of mine shafts and box tunnels.

For a corridor, you could do this manually on an iterative basis by refining the centre line of your design model where there is clash detected on one side but not the other.
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Re: Deviations in width of hallway

Post by VXGrid »

smacl wrote: Tue Mar 29, 2022 8:46 am
GCFdesign wrote: Tue Mar 29, 2022 7:47 am VXGrid

Your proposed workflow would likely return a result, likewise the opposing datum at any location would conclude in a result. However, my point is that technically either datums are not truly definable, but merely a response to the captured data, which in turn such data, however small has itself been compromised in terms of accuracy (the nature of the data we all have to deal with).
An idealised hallway centre or axis throughout the data is not known and yet again from design stage to as-built such a path centre would itself mean nothing.
Clearly the 1.83m width is the driving criteria to search fro, however, how such an envelope of idealised space is located throughout the dataset is key in performing such a search.
It could be that your suggestion and indeed other suggestions would suffice, however, from a purest point of view, it would not, however, maybe your suggestion is as close to a practical solution that can be achieved.

VXGrid wrote: Tue Mar 29, 2022 7:22 am

Can you elaborate please?
Agreed, assuming the walls should be vertical one approach would be as follows;
  • Draw a rough centre polyline down the corridor and extrude this vertically to form a set of planes / polyplane
  • Create a grid at regular horizontal and vertical intervals along the above
  • Project points left and right from each grid position intersecting the point cloud to determine the width
  • Use these widths and intersection positions for the final analysis
We do something similar in tunnelling for clearance analysis, where we move a section template along an alignment at regular intervals, fit the position of the template in section against the cloud at each interval and use the result as the new centre line for our extruded model. In tunnelling this is called a wriggle survey and can also be applied to the likes of mine shafts and box tunnels.

For a corridor, you could do this manually on an iterative basis by refining the centre line of your design model where there is clash detected on one side but not the other.
Wouldn't this mean we base our width calculations on Normals, which might not be the shortest distance between either walls due to noise?
Even if we would use the points itself from one wall to the other, we might get a sampling issue (depending how many setups we have).
Projecting single points of one wall to planes on the other wall might give the best results, but still, projecting in which direction and given that we "know" that the wall on either side might be not ideal due to construction, so our measurements will be off.

You are both right, my approach is flawed by using the beginning and end point of one wall to define a fixed plane, against which we compare orthogonal projected the point cloud of the other wall and testing if our orthogonal projected point is within this defined distance.
Defining our reference plane in another way would end in a different result, but luckily we could get the best definition by using the same feature, but within a small bounding area to check the flatness of the wall where define our reference plane.

The big question is: What is the background of the request. Is it a yes/no situation aka is everything build as defined or not, or is it a question to find out where our issue areas are?
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Re: Deviations in width of hallway

Post by smacl »

VXGrid wrote: Wed Mar 30, 2022 7:39 amWouldn't this mean we base our width calculations on Normals, which might not be the shortest distance between either walls due to noise?
Even if we would use the points itself from one wall to the other, we might get a sampling issue (depending how many setups we have).
Depends on how we define corridor width in this context. I'd think of it as the horizontal distance between two points, within a specified search tolerance, measured at right angles (or normal) to the defined corridor centre line. It is dangerous to use either wall as the reference system for projecting normals as the walls may have small variations that upset those normals, e.g. noise, pillars, doors etc.., where a defined centre line would not.

Note that you have to use some notion of normal projection here. Say you didn't, you might consider an alternative would be to cut a horizontal slice and for every point on the slice store the distance as the distance to the nearest point greater than say 90% of the corridor width away from that point. This doesn't work as there is nothing to stop you measuring between two points on the same side of the corridor.

For a robust result, you would start with an arbitrary centre line and then use a fitting exercise such as wriggle analysis to produce a more precise centre line on which to base you analysis. Important for clash detection in tunnels and shafts, probably an overkill in this scenario.
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Re: Deviations in width of hallway

Post by landmeterbeuckx »

Let me explain the situation.

Plasterboard has been installed but badly due to water coming down the ceiling, bad placing,....

A certain standard stipulates that the distance between 2 corresponding points must be at least 1.83m. IF it is less, the work will be rejected. It has to do with the possibility to move a hospital bed in the hallway.

Since both matching walls have different concave and convex deviations, it is difficult to see where exactly the problems are.

In pointcab I defined 2 points at the corners and made deviation plans per part between doorways. This way they can see bumps and cavities per section, but the distances themselves I thought to do with comparison of 2 surfaces.

Image

Image
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Re: Deviations in width of hallway

Post by kpob46 »

landmeterbeuckx wrote: Wed Mar 30, 2022 2:35 pm Let me explain the situation.

Plasterboard has been installed but badly due to water coming down the ceiling, bad placing,....

A certain standard stipulates that the distance between 2 corresponding points must be at least 1.83m. IF it is less, the work will be rejected. It has to do with the possibility to move a hospital bed in the hallway.

Since both matching walls have different concave and convex deviations, it is difficult to see where exactly the problems are.

In pointcab I defined 2 points at the corners and made deviation plans per part between doorways. This way they can see bumps and cavities per section, but the distances themselves I thought to do with comparison of 2 surfaces.

Image

Image

For this, I would use Cyclone 3DR to simply do a cloud to cloud comparison of one wall to the other. That would display a distance heat map between the two walls. This can also be done in CloudCompare.
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Re: Deviations in width of hallway

Post by landmeterbeuckx »

For this, I would use Cyclone 3DR to simply do a cloud to cloud comparison of one wall to the other. That would display a distance heat map between the two walls. This can also be done in CloudCompare.
Haven't got 3dr but i've tried some stuff with cloudcompare but the client is for the moment happy with the deviation plans and some dimension lignes. I think he will not want to pay extra for a lot of extra time spent working with these clouds.
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Re: Deviations in width of hallway

Post by GCFdesign »

Did you manage to solve the problem?
landmeterbeuckx wrote: Fri Mar 25, 2022 12:56 pm Hi,
I have a project where there is a hallway scanned but there is a tolerance of 1.83m between points on both sides of the hallway.

Plastering wasn't done up to standards so there are places where it is 1.82m and others 1.84m

How would i tackle this so i can color my pointcloud green where it is fine but red where it is over tolerance.
Regards,

Gary Fellows

Director

GCF Design Limited

https://gcfdesign.wixsite.com/gcfdesign
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