"Plot transparency" causes aerial not to plot

[Peter.NguyenUPHMM]

Every year, my organization provides new aerials (.ecw files) for us to use. With my projects, I use MAPIINSERT to attach the aerials on a layer with a Layer Transparency value of 50. Once I've completed my project in paper space, I plot with "Plot transparency" checked. With this year's aerials, however, my aerials don't plot with the "Plot transparency" selection checked, using different plotting options to verify (e.g. print, PDFs, various .pc3's). This year's segmented aerials are each about 100 mb larger than the previous year's. I've tried changing the Raster Graphics to "Lower resolution," and increasing RASTERTHRESHOLD and RASTERPERCENT to max, but these didn't work either. Does anyone know any workarounds for this issue? Using Civil 3D 2023.

[Mike.M.Carlson]

I see this behavior too. Civil 3D doesn't seem to honor the transparency band in .ecw files. The only workaround I found that works is to create an image clipping boundary using a closed polyline around the RGB and transparent edges.

It pains me to offer the work-a-round above but .ecw (despite being such amazing compression tech) is not fully supported in Civil 3D. They don't even support .ecw v3 file format yet.

I can say I even reached out to Hexagon support recently and we tried every possible method to export from GeoCompressor with various combinations of settings and Civil 3D just doesn't like .ecw transparency settings. I will say OpenRoads Designer and ArcGIS Pro had no problem with any of the .ecw files and they accept the latest .ecw v3 format. Sigh....  

[ChicagoLooper]

Hi @Peter.NguyenUPHMM 

This sounds like your ecw is a 4 channel multiband raster. Civil3D/Map3D only support 3 channels, such as RGB. 

If you or your coworkers have access to third party software, e.g., Arc Pro, Global Mapper, QGIS, etc. etc. etc., you can use it to export the ecw to another format. AutoCAD friendly formats include tiff, jp2000, jpg, to name a few. 

You may also ask the supplier of the rasters if they offer the same (or similar) image in another format. This will save you the time from performing the conversion yourself. 

[Mike.M.Carlson]

I can apply transparency (4 band) in ortho imagery all the time in C3D (tif, png, jpg)…just ecw gets messed up somehow for me.

[Peter.NguyenUPHMM]

Mike,

Do you happen to have an example of using the image clipping boundary? I usually clip my aerials by selecting the corners, but not typically using CLIP -> POLYLINE. Should I just make it the shape of my viewport? And how do I separate the RGB and transparent edges?

Thanks,

Peter

[Mike.M.Carlson · Accepted solution]

Hi,

no example, but I can walk through steps 🙂

1. draw a poly line around the limits of RGB / Band 4 interface
   
   
2. select image and in contextual Ribbon, look for Clip Image
3. at command line select poly line object and select your polyline

this clips out the ;th band regions that are not honored in C3D for .ecw

[Peter.NguyenUPHMM]

When I do this, my whole .ecw disappears (rather than simply clipping outside the boundaries of the polyline).

[Mike.M.Carlson]

Please select Invert Clip at command line. maybe your default settings are backwords.