heightfield shader border blend

Started by Ashley, March 19, 2015, 02:45:53 AM

Previous topic - Next topic

Ashley

Heya,

The border blend attribute on heightfield shader nodes defaults to 0.1.
This isn't so good when loading multiple dem files. Is there a way to set it to 0 as default?

Cheers

Dune

I don't know, but it might work if you make your own default scene with the right settings, save it and open that every time.

bigben

#2
I don't think so, although you could load your DEMs, save the file and do a search and replace on the TGD in a text editor. How much effort is justifiable depends on the number of DEMs you're loading I guess.

I normally just disable the stitchable border which in the TGD file appears as
stitchable_border = "1"
replace it with
stitchable_border = "0"

Alternatively you can use a program like QGIS to merge the DEMs into a single (or at least fewer) files.  It might be nice to have this as a configurable preference. Enabled is good for overlapping DEMs (e.g. mixed data sources), disabled is good for tiled DEMs

chrisshort

Quote from: bigben on March 19, 2015, 06:15:01 AM

Alternatively you can use a program like QGIS to merge the DEMs into a single (or at least fewer) files.  It might be nice to have this as a configurable preference. Enabled is good for overlapping DEMs (e.g. mixed data sources), disabled is good for tiled DEMs

What would be the procedure in QGIS to accomplish this? Your last tutorial to get georeferenced image maps using QGIS worked great!

Thanks!

Ashley

Thanks bigben that code solution is good to know. I'm using DEMs more and more these days so I'll check out QGIS.

Cheers  :D

bigben

I suspect this should be relatively straight forward in QGIS if you've downloaded the data. I'll have a look a little later, but I'm hoping that it will be a case of drag and drop data files into it and then export via the Convert menu.  I had a quick hunt around for accessing the USGS 10m NED directly but finding the right URL for the right WMS connection seems to be much harder than it should be.  At least I now have a much greater appreciation for my investment in GlobalMapper where they appear to have moved all of the hard stuff out of sight of the user, providing a useful array of online data sources out of the box.

chrisshort

Thanks! I do have the data already. it would be more convenient if they were combined.
Chris

bigben

hmmm... QGIS is a whole different world to what I'm used to. Looks like it's mainly for analysis, but you can make it do stuff like this.  Looking for a simple tutorial for it as it's not the easiest program to use. 

In the meantime, this is how I do this sort of stuff. https://www.youtube.com/watch?v=kHqa9CE7Wyw  Dropped the screen resolution for the screencast, but you get the idea of what sort of line of sight can be achieved with a very small payload.  The one thing that's not entirely obvious is why I load my global DEM set.  This essentially acts as a hole filler for anywhere where the line of sight extends beyond the limit of the high res data.

chrisshort

Thanks for the video.  What I'm noticing with the DEMS I got from the National set (Arc Grid 1/3) was 4 quadrants (I selected the largest file out of the group of files in the zip, Was there a specific one I should have loaded? *.adf file)

Upon loading I don't get a seamless edge between the groups. A depression seam between all bordering edges. I've worked with other types dems and such and didn't have this issue. Was wondering if I missed a step.  Would like to avoid boarder blending if possible.


bigben

#9
The depression seam is due to border blending, which requires edges to overlap.. Uncheck the stitchable border box if your DEMs share the same coordinates for the edges. The edges are being blended with nothing so the altitude lowers towards the edge.

From what I gather of QGIS, it's a bit more like Photoshop than GlobalMapper. You can load multiple DEMs but you have to merge them together first, load the merged result and then export that. It doesn't seem to distinguish between DEMs and images, it just treats everything as images and most functions seem to only operate on a single image.