Problem Importing GeoTIFF Terrain Into CityEngine

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02-06-2014 06:23 PM
by Anonymous User
Not applicable
Original User: ForgeSouth

Hi everybody,

I am new to CityEngine and to GIS. I am a hobbyist doing 3D and now am looking to do a recreation of the city I grew up in in South Africa. I am using GlobalMapper 15 and have generated a GeoTIFF file (headers included) as well as a world file (TFW) and a PRJ file. Those two files are separate from the GeoTIFF file.

When I import into CityEngine it reads the terrain bounds and resolution just fine, no problem. The issue is that there is no elevation data in it. It is just basically a texture. I have imported it using the Layer>New Layer>Terrain method, but as I say, no elevation information. The source of the data is an SRTM 3-Arc Second overlay.

I have used 2 export methods in GlobalMapper (Export as Raster Image and Export Elevation Grid Format) but both produce the same problem.

I have also read on in the resources for ArcGIS CityEngine that if there is no elevation data in the image, CityEngine will automatically search for a TFW or PRJ file in the same folder to extract the data, but I have placed all files in the same folder an it is not making any difference. I have also made sure that the header files are written into the TIFF (that's why it is importing correct bounds etc...). The only problem is elevation data.

I have attached all the files, and also some files for Cape Town (even Table Mountain comes out flat on the ground). I would GREATLY appreciate people's help and guidance!! As a hobbyist, I cannot afford ArcGIS mapping, so I have to stick with GlobalMapper (but it seems to be fine), but I would really deeply appreciate assistance!!

PS. I am a layman, so please try to respond in layman's terms :D

Thank you in advance!!!
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6 Replies
MatthiasBuehler1
Frequent Contributor II
Please anybody help Andrew, since I'm no GIS specialist and don't know GlobalMapper ..

Thanks ! :)
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by Anonymous User
Not applicable
Original User: ForgeSouth

Anybody?! Please!!
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JosephMcGlinchy
New Contributor III
Hi Andrew,

I think it may be a problem of vertical exaggeration. CityEngine, by default, sets the max brightness for the terrain layer to be 100.0 and I think your max elevations are larger than this. The maximums I see for Cape Town and Johannesburg are 246.0 and  196.0, respectively. If you make the TIF file the input for both parts of the terrain layer (terrain and texture), you can change the maximum value in the import wizard (under maximum brightness value) or in the Inspector window if you select the terrain layer. At the very bottom you can change the 'elev' attribute as follows:

attr elevation = map_01(brightness, 0.0, 246.0) + elevationDelta


Try that, and hopefully it works! When I imported those files directly with the defaults, the areas look flat. But changing this maximum 'brightness' value should give you the relief you want, no pun intended.



Cheers,
Joe
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by Anonymous User
Not applicable
Original User: ForgeSouth

Hi Joe,

Thanks so much for your response!!

Indeed, I did try the max elevation increase when importing, but that resulted in a kind of perlin noise generation that exaggerated the terrain on what seems to be a pixel points basis. Having lived in Johannesburg all my life I can safely say that the terrain definitely does not look like that haha!

For Cape Town, Table Mountain actually rises up 1100m above sea level, so 246 is well well below what it should be. As far as I can tell from all my readings is that the GeoTIFF file should automatically include the elevation data anyway and that one should not need to adjust anything (size, bounds, scale and elevation) when importing the file. I am wondering why I am not getting the elevation data in the file whilst still getting bounds and scale data.

Perhaps it is more an issue with GlobalMapper than with CityEngine...
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JosephMcGlinchy
New Contributor III
Hi Andrew,

Yes, please double check the output GeoTIFF that represents your elevation data. Make sure those values are consistent with what you know to be true! Otherwise, your input in CityEngine will not look correct either.


-Joe
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by Anonymous User
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Original User: joemcglinchy

Andrew,

I scaled the GeoTIFF you provided for Cape Town to make sure the max elevation is 1100.0, essentially multiplying every pixel by (1100.0/ 251.0), since 251 was actually the maximum value. I did this on the first band of the image.

It looks like the software you are using is creating 3 band UINT8 images out of the elevation data...not quite what you want. I included this processed file for you, perhaps it is more reminiscent of what you know?
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