While playing around with my loaded DEM maps, I'm noticing an issue with adding water where it doesn't seem to appear in areas it should be. In the attached screen shot, there is a flat like area that is definitely below the higher land areas. By placing the cursor in that area, it says the altitude is below 0 in most cases. The water elevation is well above zero yet is seen stopped at this area from appearing but not to adjacent areas. Any clue as to why the DEM map is not allowing the water to cover areas it should be?
Hi,
Just a guess here...
Your DEMs cover a fair sized area ?
Have you used a Lake to add water or a sphere with water shader ?
If you use the former, if I remember correctly it is basically a flat disc that doesn't take curvature of the planet surface into consideration. I'm sure I'll be corrected swiftly if my assumption is incorrect.
Rgds
Chris
Lake. Must be the issue.
Didn't know I needed (or could) to go planet level of water. Thought Lake was my only option. Thanks and I'll start reading up on this!
Hmmm...let's have a look at your screenshot:
The lake has a 300km radius and is ~60km away from "origin" (= 0,0,0 coordinates).
At these coordinates, away from the origin where the altitude and Y are the same, there's a discrepancy between Y and "altitude".
You can see this by the different altitude settings in your lake object.
Y is 200m and altitude is 782m.
The further away from 0,0,0 the more discrepancy between these 2 coordinates arises.
This is what red_planet describes in more easier words.
Solution:
1) transform your scene closer to 0,0,0, using a transform shader
2) red_planets' suggestion to add a second planet at the same position as your normal planet. Increase radius with 100m if you want 100m water level etc.
I'll dig up some useful reading on the coordinates issues when I'm home.
Matt has written some useful information about this in the past.
Cheers,
Martin
Here's some info from Matt about this:
http://www.planetside.co.uk/forums/index.php?topic=6701.msg71067#msg71067
http://www.planetside.co.uk/forums/index.php?topic=9512.msg100839#msg100839
http://www.planetside.co.uk/forums/index.php?topic=5686.msg59609#msg59609
Thanks for the reply's. I am noticing that the issue may ultimately stem from the DEM, which was converted to a TER file out of Global Mapper. The bounding box of the DEM is not curved to the Planet, thus making a whole section higher than it supposed to be. I think it was mentioned that Georeferencing may be an issue but I don't know. Attached is a colored screen grab showing the blue areas that are above 400 meters. The flat area should be around zero but it is not.
Update: Just added a screen shot of the Dem's Bounding box which is clearly off the planet....
Update:
After reading all the links, I placed the DEM at 0,0 centered and then unchecked Flatten First. This improved the elevation significantly.
So with importing DEM files, the procedure is:
Location Tab in Heightfield Shader/ Position Center checked and Position 0,0
In Displacement Tab, Uncheck Flatten Surface First
Just wanted to put this in clearly in case someone else searches for the same thing.
Let me know if there is a better way of doing this.
The Lake object is curved with the planet. The lake has the same altitude all across its surface, but altitude becomes different from Y as you move away from the origin.
Matt
It indeed is! Never realized it, just checked. Thanks for telling us, Matt
Plus keep in mind that when you point your mouse cursor in the 3D preview that it shows "Y" and not "altitude".
Which is why I always right click and "Copy Altitude" and paste in a text editor to get the correct info... ;)