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Home - General / All posts - Visual resolution problems on draped orthophotos?
sjvanek10 post(s)
#18-Sep-14 14:55

Hi, is there a way to increase the resolution of draped imagery? it seems to me that Manifold defaults to the resolution of the underlying surface (terrain) - e.g. 30 m for an ASTER DEM, when draping imagery. So beautifully crisp orthophotos are degraded when overlaid on the terrain.

This is partly a function of the high resolution of the imagery; from a distance it looks fine, and kudos to manifold for making it so incredibly simple to visualize this.

I have tried increasing the pixel dimensions of an extracted image as suggested by manifold documentation, which produces nice clear terrain features but the overlaid image is still grainy.

image attached

Attachments:
ASTGTM2_S02W079_dem Terrain Image 2.jpg

tjhb
10,094 post(s)
#18-Sep-14 23:51

it seems to me that Manifold defaults to the resolution of the underlying surface (terrain) - e.g. 30 m for an ASTER DEM, when draping imagery. So beautifully crisp orthophotos are degraded when overlaid on the terrain.

You're right. For now the way to avoid this is to resample the terrain to match the resolution of the imagery.* Obviously that creates a lot of extra memory overhead--but it also avoids the necessity to resample the imagery on the fly, so CPU load may be reduced overall.

*The quickest way to achieve this is to place image and surface together in a map, right click the layer tab for the surface, and choose Match. Accept or choose the image as the target.

sjvanek10 post(s)
#19-Sep-14 20:34

Wow, ok, that was quick to convert. Now there is a slight additional problem, I can only see a very small patch of the terrain at a time, as if Manifold only has the capability to display a certain n x n pixels? Can that be changed in settings or some such? I looked but have not found something yet.

If I can just see more than 200 x 200 m or so it will look amazing!

tjhb
10,094 post(s)
#19-Sep-14 21:53

Terrain > Surface > Display.

dale

630 post(s)
#19-Sep-14 23:21

Read the terrain bit in the manual for performance tips. Turn off clouds, fog, and gradually increase the distance from 4 upwards. Change details to low, then once you have your view composed, change to high and re render.

For more search the forum.

tjhb
10,094 post(s)
#20-Sep-14 01:37

I got quite a bit out of re-reading that at your suggestion Dale. If there ever were a book that repaid repeated readings, the Manifold manual is it.

dale

630 post(s)
#20-Sep-14 12:48

Agreed, I've had plenty of time to read up on terrain rendering speed, while waiting for a terrain screen redraw

sjvanek10 post(s)
#23-Sep-14 06:05

Thank you thank you thank you for the help. My graphics card is not fast enough to render a 15000 x 15000 pixel image matched to the DEM, so I also found it necessary to use resize to get the image down to 1/5 size, 3000 x 3000 and only then match to the DEM - with that I can compose the view in 16-tile mode in terrain-surface-tiles, and then gradually expand outward to 50 tiles and high quality for final rendering. From a virtual distance of about 1 km oblique the result is pretty stunning, and very helpful for our project team.

Maybe I'll head to a University computer lab and search out some faster graphics cards to compose a number of additional views, and with a less resized image. Very cool.

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