Question

Draping extruded polygons on draped raster causes offset

  • 29 June 2018
  • 5 replies
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I am generating a 3d pdf file.

I have draped a tif file over terrain and then draped polygons for the same area. The fact the entire tif drapes to the terrain and each polygon drapes over the terrain seperately creates offsets between the raster and vector.

Is there a transformer to resolve this? Perhaps I can merge the building polygons so they drape to the surface as one feature? I'm unsure what transformers will help me acheive this?


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Hi! We need more info to be able to help you.

Is your TIFF file geo-referenced (in other words: is it a GeoTIFF or is there an auxiliary *.tfw file)? Are your polygons geo-referenced? If all can be answered with yes: do both inputs have the same coordinate system or projection?

If this all checks out: which transformer(s) are you using for the drape and what are the settings?

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Hi @proudgis,

I am not sure how you draped the tif over the terrain, but the best way would be to set the tif as an appearance on the terrain surface using the AppearanceSetter transformer.

In the AppearanceSetter parameters, please set Texture Coordinate Generation Parameters - Texture Mapping Type to Top Down Georeferenced. This will use the tif georeferencing to properly align the image to the terrain. Write the textured terrain to the PDF instead of the TIF file.

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Thanks for the suggestions @DaveAtSafe, @sander. I can confirm all files are georeferenced correctly. I have attempted the changes to 'Texture Coordinate Generation Parameters' as suggested and this made no change. The FMW in use is copied below, along with the full PDF image, which might show the issue more clearly. The lower terrain at the river draws the tif image in, leaving building overhang on all sides.

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Thanks for the suggestions @DaveAtSafe, @sander. I can confirm all files are georeferenced correctly. I have attempted the changes to 'Texture Coordinate Generation Parameters' as suggested and this made no change. The FMW in use is copied below, along with the full PDF image, which might show the issue more clearly. The lower terrain at the river draws the tif image in, leaving building overhang on all sides.

Hi @proudgis,

 

Hmm.. looking at it from above, it actually seems to be more of a scaling issue than an offset issue.

 

Since you are using a CSV to create your terrain, I'm just checking one more time: you did set the coordinate system parameter on the CSV Reader to match that of the building features, right?

 

Other than that, I don't really notice anything strange in your workspace which could lead to an offset/scaling issue. However, you might want to replace the TINGenerator and SurfaceDraper transformers for one single transformer: SurfaceModeller. Not only is this more efficient, but we lower the risk of any possible spatial mismatch.

 

Please give it a go and let us know if it helped...

 

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Hi @proudgis,

 

Hmm.. looking at it from above, it actually seems to be more of a scaling issue than an offset issue.

 

Since you are using a CSV to create your terrain, I'm just checking one more time: you did set the coordinate system parameter on the CSV Reader to match that of the building features, right?

 

Other than that, I don't really notice anything strange in your workspace which could lead to an offset/scaling issue. However, you might want to replace the TINGenerator and SurfaceDraper transformers for one single transformer: SurfaceModeller. Not only is this more efficient, but we lower the risk of any possible spatial mismatch.

 

Please give it a go and let us know if it helped...

 

SurfaceModeller hasn't made a difference to the output unfortunately, but I will use this efficiency reasons. I have however resolved the issue. The main thing I overlooked was that the appearance setter seems to overlay the raster in a way that fits the extents of the grid regardless of raster size. The problem (I think) is that although the raster and the terrain are the same extents, the xyz lists the centre-point xyz of the cell which I hadn't factored in the cell size. Using the bbox of the 3Dpointreplacer as the clipper has now aligned the raster as expected. Thanks for the help!

 

 

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