Face normals of the imported building models

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12-19-2013 12:05 AM
GucluSen
New Contributor
[ATTACH=CONFIG]30003[/ATTACH][ATTACH=CONFIG]30004[/ATTACH][ATTACH=CONFIG]30005[/ATTACH]

Hi,

When I import a 3D shape model from another software, CityEngine views these models in project correctly.

But I want to publish these models on web scene, because of the face normals of the polygons, 3d models seems to be partially.

I can not change all of the polygon's face normal one by one manually.

Whole polygons are separate, they are not combine building by building

How can I correct the face normal automatically on  the building models from inside to outwardly?
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5 Replies
by Anonymous User
Not applicable
Original User: garsdaledesign

This happens a lot, it depends on the source of your model.   If you use the "Scene Light" button you can see which faces are reversed (colored in black) and therefore will be see-through in webscenes.    If they consistently are all the wrong way then CityEngine has a reverse normals (right-click) tool.   

If its a small to medium model I use sketchup and a tool called FrontFace (obtain here).  You can then use a style that highlights the faces that need changing... and just move your mouse over the face with the tool works easily and isn't too fiddly...

Hope that helps!

Elliot



[ATTACH=CONFIG]30003[/ATTACH][ATTACH=CONFIG]30004[/ATTACH][ATTACH=CONFIG]30005[/ATTACH]

Hi,

When I import a 3D shape model from another software, CityEngine views these models in project correctly.

But I want to publish these models on web scene, because of the face normals of the polygons, 3d models seems to be partially.

I can not change all of the polygon's face normal one by one manually.

Whole polygons are separate, they are not combine building by building

How can I correct the face normal automatically on  the building models from inside to outwardly?
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MatthiasBuehler1
Frequent Contributor II
Hi,


Note:

In general, this process can not be done 'all automatted', neither in CityEngine nor in any other application. Reason for this is that it depends heavily on the model itself and on the polygon-connectivity.

Example:

Of you have a cube, where each side has been moved 'out' a bit, so all the faces are disconnected: How is the computer to know what's inside and what's outside if it's just 6 separate polygons ? :) That makes the task very difficult.

matt
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by Anonymous User
Not applicable
Original User: gsenyurdusev

Hi,


Note:

In general, this process can not be done 'all automatted', neither in CityEngine nor in any other application. Reason for this is that it depends heavily on the model itself and on the polygon-connectivity.

Example:

Of you have a cube, where each side has been moved 'out' a bit, so all the faces are disconnected: How is the computer to know what's inside and what's outside if it's just 6 separate polygons ? :) That makes the task very difficult.

matt



Yes, this is very difficult but it has too much works to cover texture all 3D polygons that is produced by using Lidar datas and lots on polygon's face normal is different direction.

May be practicable to use CE SDK.

Thanks,
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PaulCote
New Contributor III
I have the same problem as described in the original post.  My question is whether this problem of flipped normals is a problem with the data or whether it is a problem with City Engine.  I'm still using 2012.1.   I wonder if I should ask my data vendor to fix the problem.

Thanks
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by Anonymous User
Not applicable
Original User: matthiasbuehler

Hi Paul,

It's not a problem of the data, since either way a normal points, the data is valid. It's just what we interpret visually, and that's a whole different story ( see posts above ).

In general, yes, you should ask the data provider if they have methods to provide data with 'better' normals. But I assume they won't be able to provide data that needs no manual rework.


Matt
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