Hi Alex
sorry for the abbreviations. I live in this stuff and forget it is all geek speak.
DTM = Digital Terrain Model, sometimes called a Digital Elevation Model in the USA. This is usually a rectangular grid with elevations at the grid nodes.
ECEF = Earth Centred Earth Fixed. this is a well used coordinate reference system for representing a 3D latitude, longitude and elevation in a simple X,Y,Z where the origin is at the centre of the earth.
http://en.wikipedia.org/wiki/Geodetic_s ... oordinates. this coordinate reference system is used by planet apps such as google earth, NASA worldwind etc. it is easy to transform back and forth from a lat/long to an ecef. ECEF's are good as the plot with ease.
For us, a terrain is a real terrain of observations of the earths surface. we survey the earth and oceans, and view it in 3D space. We are looking at OGRE to replace our existing OpenGL codebase. we envisage generating the mesh data for the earth surface (based on real time surveys) and supply it to your 'terrain handler'. does that sound correct?
It is good that you are using double precision numbers. we tried using floats, but ECEF's (in metres) from the centre of the earth are problematic. you get truncation of the big numbers, so jitter in the rendering.
We are developing in c# so are helping out with the mogre wrapper. it is going quite well.
I am interested in how well your roam engine behaves. we have studied this in the past, but the popping and tearing at the sides was always a problem. It would be great if you have this sorted.
We are old hands at terrains, but new to ogre. however we are beavering away here in Perth, and will be in a position in the near future where we will nned to decide which way to go to get massive terrains into our scene. By massive I mean billions of elevation observations. do you believe your system can be of use? if it is close, i am interested, but if you are a way's off, we will investigate sinbad's implementation of terrains, and figure out how to use them with ecef's. failing that, we will probably implement the hoppe lod engine we are already familiar with. having said that, reinventing wheels is not something i am fond of, so if you are close to release into the wild, i would like to take a look before deciding.
regards
pk