up scaling terrain

[SeerBlue]

hey again, first of thanks for a great program, I have been using it quite a bit lately, trying to learn as much as I can as part of the Medem Project, and with VTP (just never end up capturing any screen shots).
Got a question, when I resize the terrain tiles up, and it does an excellant job up to 10k square, I get a 1 wide pixel drop off in the elevations on the top and right side of the terrain. I am guessing this is because it goes from bottom left to top right during rescale. It is not a real problem as the resulting seam can either be cropped out in GM (it's just 1 pixel, who needs it ) or digitized out with GM's contours,,, so, back on topic, I noticed when i use the design map instead of import height field there is an option to wrap edges, would this remove the drop off by repeating the edge or am I thinking wrong here. I have run a 5k resize to 10k tile thru once, but I didn't pay attention to the erosion/terrace settings and lost alot of terrain, so I am not sure if the edge wrapping got rid of the drop off or I just eroded it away.

[Aaron]

Hi SeerBlue,

I didn't realise there was a problem with L3DT's resizing, but I'm not surprised to hear it either. Those bits were written quite a long time ago, so there's a good chance they're not entirely kosher (may not be double-precision). I'll have a look into it.

The 'wrap edges' option is probably not what you want. It makes the map appear seamless by wrapping-around the left and right edges, and the top and bottom edges. This amounts to a toroidal-world, which some renderers use to approximate infinite terrain. So, only use this feature if you want the elevation at the edge of the map to be the same as at the opposite edge.

Cheers,
Aaron.

[SeerBlue]

thanks for the quick reply, Its not a real problem, after thinking about it for a bit more, I came up with a few more options to work around it. Resize up a little larger (2 pixels) than where I want to end up and trim back to the needed size, as the last elevations before the drop are spot on, or resize to the needed size , trim the drop and then open each tile in turn in Global Mapper and generate contours, and then open the generated contour workspaces at the same time and the break in the contours can be healed easily in global mapper. Anyway this is all just to try to figure out the best way to upscale and downscale the MEDEM tiles as they are terraformed to our map and then remerge them seamlessly. So far L3DT's rescaling is the best and definately the easiest to use, Leveller works good but gives me fits as it is not a simple one step operation, and Global mapper can only change the horizontal and vertical scale thru xyz .asc export, not bad for small terrains but a killer for large ones. And it may just be that it is apperent because I am going from a relatively small tile to a pretty big one. Going in one step produces the least drop, multi stepped rescale seems to compound the width of the drop.
Probably more info than needed, but it may come in useful for some one else, that's how most of my questions get answered, reading replies to some one elses post. SeerBlue

[Aaron]

Hi SeerBlue,

It's fixed. It was a silly coordinate-mapping error. I've also added a progress bar to the resizing calc (with a reliable time estimate), and removed that stupid "warning: size is pretty big" message.

The fix will be included in the next release.

Cheers,
Aaron.

[SeerBlue]

WOOOT, great news, as all 40,000 vtp .bt tiles will soon be going up on the FTP at ME-DEM. (right now UPS is whisking them across the country to Java).
Thanks for all the work you have done and advice given. SeerBlue

[SeerBlue]

just a note to say the upscaling works perfect in the beta for 2.4. SeerBlue