How to design a scene with existing buildings, and using existing data best workflow.

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06-27-2014 05:12 AM
KennethLindhardt
Occasional Contributor
Hi,
Will start this thread, by saying that I�??m amazed by CityEngine. And love to be the one that are responsible to get this out to the public in Denmark. Just wanted to set things straight if my perversely posts haven�??t explained that probably ;)

I�??m still struggling on which workflow I should use, to create existing buildings in a area of interest. I told in an earlier post that we were receiving  Lidar data with 40 x 40 cm of density in average. Those data will be free for everyone in Denmark, and of course I would like to use that data to create 3D content inside CityEngine. ( I know CityEngine don�??t manage Lidar)
I mention before that I�??ve been working with GIS before, but BIM and 3D visualization is my core competence. So I�??m no GIS expert, but I do work together with a lot of GIS geeks.
My problem is that I can take my building footprints, assign lidar data, and get the height at an attribute like we know from Redlands Redevelopment. But with 100 of different roof types, and even a lot of different roof types within the same building polygone, I�??m having trouble to see how I would create that. I do not see a straight line to follow, so I can build up a rule that could get even close to that. I�??m not talking about the prober facade texture for each building, but just to get the geometry right, or almost anyway.

I have a colleague who is willing to help me. He have created multipatches from our Lidar data, and I hope that you guys have maybe another solution, or a way to clean out those multipatches. I have no trouble seeing how the building should look like, but I would like the building to not be that shaky.

Any good ideas workflows? Am I on the wrong track or?

Left attached picture is the multipatch in ArcScene the the right CityEngine
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5 Replies
by Anonymous User
Not applicable
Original User: kelin84

Let me clarify what I would like to know. I�??m currently not locked on a workflow. I�??m just thinking that there would be a clever way to use the Lidar points, to get the geometry of my buildings.
This is just my thoughts on it so far. My big issue is the roof form for my buildings.
I got a lot of information for my building footprints, that I can use to build up my 3D geometry.
1. Date of built
2. Building use
3. Facade material
4. Roof material
If I create a rule that use these information, I could get pretty close to the architectural design. I know how a school from 1952 would look like, it would be red tiles, white window frames and a red tile roof. So that was my first thought on how to create the building design inside CityEngine.
Now we got our Lidar. To get the building height would not be the problem, but to get the prober roof type and angel automatically is where I�??m stucked at the moment. What have been done to figure out the roof, is it�??s a random procedure? Or is it possible to use something like my multipatches, clean em up, to only use the points where there is significant change in the angel of the point. It could be nice to clean the multipatch up, so it only have 4 point of a roof side, to create only one polygone, instead of all my vertexes as I got now.
Another thing could be to get the min value from my Lidar and assign that value to my building fooprint. Then use the MIN value, and on top of that create random roof, But if the building have an entrance with a little roof on top in a height of 2 m, but the real roof start at 4 m, then the building height wouldn�??t be close to the real height. Has anyone working with a solution that could filter out the �??to MIN�?� points. I�??m thinking about something like: �?? choose the significant MIN, within 20 cm�?� Then it would filter out the two Lidar points that hits the entrance, but don�??t know if that is even possible.
I know this maybe falls a little out of CityEngine, but I guess the the CityEngine people would be the first to explore this.
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MatthiasBuehler1
Frequent Contributor II
Hi,


I don't have all the expertise needed for a clear answer to this.

I have forwarded this thread to some people and I hope you get an answer soon, ok ?

Matt
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by Anonymous User
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Original User: kelin84

That�??s not just OK Matt, that�??s awesome. Thank you for always providing a great service
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KennethLindhardt
Occasional Contributor
I was just exploring the London Example Scene: http://ow.ly/tfqKA found on the CityEngine facebook page.
I�??ve never been to London, but I can tell that the roofs are spot on, from an orthophoto.
See this is where I want to be, in fact it is much better than my first goal. Since this is an extract, from a larger model, I�??m wondering how they done that, without having to model every single roof.
So with all my writing in this post, I could get it down to: �?? I got some free data available, and my goal is to get it close to the London example.
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by Anonymous User
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Original User: garsdaledesign

Hi!  I thought I'd jump in here since it's my webscene you've looked at!   There are two questions I think here:

What worfklow(s) can be used to use Lidar data to get the correct roof types in CityEngine?
and
How was the London model achieved?

Well the sad news is at this moment in time I'm not aware of a way of extracting roof type information from Lidar to use in rule file.   As you have indicated there maybe a way of finding roof angles and lines by doing calculations on the data but this is never going to be perfect.   You still need a bit of extra information to start the process highest ridge height, eave height then an orientation, and a roof type (hip, gable etc..).   The person who cracks this will be a legend within CityEngine circles! (sorry Matt!)

As to the London model this is plain and simple CyberCity3D data data.   I use it as it plays nicely with CityEngine and ArcGIS (as well as collada format).   I'm also the UK contact for this company and help them with integration in CityEngine.  

The key to CityEngine is knowing what data to use and when.... :) 

My suggestion for you is start by assigning the 2D polygons the lidar data heights (eave and ridge maybe or max and min).  Use CityEngine to take those values to get you your heights.   Now for the most part this kind of modelling I've always regarded as background stuff so a rule file that reflects a region's building style is better than nothing yes?  Use real 3D models for small specific areas of interest.   Mix and match simple block models have been used by urban designers and architects it's not really any different now.

Hope this helps a little?

All the best

Elliot


I was just exploring the London Example Scene: http://ow.ly/tfqKA found on the CityEngine facebook page.
I�??ve never been to London, but I can tell that the roofs are spot on, from an orthophoto.
See this is where I want to be, in fact it is much better than my first goal. Since this is an extract, from a larger model, I�??m wondering how they done that, without having to model every single roof.
So with all my writing in this post, I could get it down to: �?? I got some free data available, and my goal is to get it close to the London example.
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