Terrain Models vs. Terrain Displacement

[mfured20]

Hey Guys!

 

I hope I am putting this in the correct forum. I am looking to do some physically accurate terrain work in the Smokey Mountains. My initial plan was to use DEM information exported into 16bit tiff grayscale images and use them as vraydisplacement, inspired by the work ideas put forward by Eric Hanson's Gnomon Workshop disk 'Digital Sets 4: Image Based Terrain'.

 

For those that haven't seen this disk, the basic plan was to take Digital Elevation Model [DEM] available thru the USGS, convert it to a 16bit tiff using some fairly antiquated opensource software, and apply it to a plane using vray displacement. This creates an image plane essentially 6 miles x 4 miles. This size allows me to see rolling hills wandering off into the distance, ane I bet would look amazing with some Fog.

 

Now for the bad news: I can't get any of that aforementioned antiquated software to work. After much searching, I decided to just use the .DEM and .DDF importer to bring the info into max, but the mesh it makes is outrageous, and is overpowering my poor little 32bit machine.

 

So, finally getting around to my question, do you guys, when trying to copy terrain directly, use vraydisplacement or meshes to do it? I have never actually tried before.

 

Thanks for reading my ramblings, and thanks in advance for any advice!

 

- Matt

[ctk111]

That's a fairly large area and you might be limited by your machine. How many segments do you have on the plane you've placed the modifier on? Maybe you can reduce that number. Another option would be to bring your DEM data into something like ArcView or it's equivilent and adjust the elevation parameters. I forget what it's called, but essentially you're redistributing the gray scale color value by grouping more elevations together and therefor reducing the variation in color.

[mfured20]

I have thought about using different planes to put the displacement on, but I havent been able to generate a black and white image from the DEM to use as displacement at all. I'm trying to figure out how to get that DEM info into max in the most efficient way.

 

I have used wave textures to simulate the ocean on large planes before, and have tended to break the plane up into essentially 20x20, sometimes more depending on the size. It has worked very well.

 

In terms of generating this DEM from the raw data file into a 16bit tiff... it only comes in at, say, 1300 x 1600 pixels. The only way it works is because of the depth of gray in 16bit format, using some 55k shades of gray in that smallish texture. I don't know how that will change the way vraydisplacemnt works.

 

anyway, thanks for the advice, I will definately try to break up my planes if I can ever get the displacement map to work. I'm just using the default max one at the moment, and i guess its working... sorta...

[mfured20]

Well Guys and Gals, I went and did it again. I came up with a solution that I am sure I could have come to if I hadn't been impatient and posted up here.

 

In any case, I will share with you what I have learned.

 

I last left off by downloading a DEM of an area in the Smoky Mountains and I imported it directly into max. Max brought it in as a mesh with 3.6mil vertecies at real-world heights, meaning that the valley floor I wanted to work on was already at aprox 4000ft. The filesize was tremendous, and that was before I had put in any trees, cars, or the building itself.

 

In my effort to find a work around using displacement, I found this oldschool little reader called 3Dem that allows you to view DEM files and make sure you have what you need. Under File it has an option to export the DEM to a .ter file, which is the filetype used by Terragen. I then downloaded Terragen to see if it was something I would be interested in buying, and found it to be a kinda strange working environment. Furthermore, while I could import that DEM info just fine, I couldn't seem to export it in a format that would work for displacement.

 

After a bit more poking around, I gave up on Terragen for this application and decided to try World Machine. After playing with the program for a bit [really powerful program, but steep learning curve], I figured out how to import the .ter file and export it right to a 16bit tiff. The only problem is that until I purchase the full version, it limited my exported tiff size to 512x512.

 

I then went back to max and was amazed to see that the 512 file size was sufficient to give a very decent mountainscape. I guess that 16bit file really does have a lot of info in it.

 

in any case, I have attached on here the things that I have done. The first image is the one that I acheived from just straight importing the .DFF [DEM] file. The texture on it is just a USGS topo map, and its UVW mapping is a touch off to boot. The other image is the vray displacement map at 512x512. both images were rendered at 3000x2250, displacement in 2:22, and the mesh in 2:09. There seems to be some corruption in the imported mesh too, which is absent in the displacement.

 

its pretty dam close, all things considered. now for trees and fog!

[Nic H]

how do you go about placing trees on a vray displaced surface seeing as though it only shows at rendertime?

[mfured20]

Yo Nic -

 

My original intent was to create a pysical mesh displacement generated from the same vray displacement map and use it as an object to scatter my trees on. And actually its worked out pretty well, in some ways, its even better than the vray displacement.

 

I think the best way to show what I had in mind is with an image. The attached image is split into two sides: on the left half is a mesh that I made, using the exact same displacement map, from the normal displace modifier on a plane with 1000x1000 subds. On the right half is the vray displacement off of a plane with 4x4 subds. The dividing line is kinda hard to see, but its actually off to the right of center a bit. The displacement side is certainly noisier.

 

When I started out, I figured that any mesh that I could make would be either simple and too facetted to use, or smooth and too big to use. This notion is what promted me to try out displacement. But this 2mil poly displacement mesh is pretty smooth [except for some obvious facets in the shadows], and while it is a little slow on my computer, it might be worth using in the future. I will use it to scatter proxied trees on, and I may use it for the final rendering, depending on memory issues.

 

Oh, and FWIW, at 3000x1688, the mesh rendered in 1:26 and the displacment in 1:50.

[mfured20]

Hey guys, just thought I would let people know how this worked out for me.

 

Using the physcial mesh for scattering the trees worked pretty well. I used the GroundWiz Planter Lite plugin, and I really liked it. The Lite version is limited, tho, but it worked well enough for my test. I will have to test the full version against vRay Scatter to see which I will actually invest in.

 

I scattered 57,000 groupings of four simple trees over the scene because thats all my 32bit machine could handle. I had to supplement the detail a bit with some simple bumpmapping. The trees themselves are just spheres mapped with opacity and with a noise modifier applied; for this application they will work just fine.

 

When I had finished scattering the trees, I deleted the physical ground meshes. I had thought that things would be ok with them, but the geometry started weighing very heavily on my RAM, and I would crash out pretty frequently. I ended up with a plane with vray displacment on it, just like I had originally intended. Even with all the trees, the file size [compressed on saving enabled] was only 1.7mb with just over 2mil polys. The texture I used is pretty crappy, but it will work for me right now; it was generated from satellite imagery with some painting added.

 

When I had finished with the scattering, I started playing with the vray fog feature. It's great, really easy to use. I spent about 5 hours playing with it, but I like the effect I came up with. When I finally get to the real image, I will put in more fog I think, especially if it is dusk.

 

So, just to recap: Plane with vRay Displacement for the terrain, vRay Sun/Sky, Vray Fog, tree scattering of vRay Proxies using GroundWiz Lite. Image at 3000x1689 rendered in 50m:42s.

 

Hope this thread helps people fumbling with the same issues!