[OpendTect_Developers] Body construction in OpendTect and related

[Yuancheng Liu]

Dear all,

it is a very interesting and challenging topic for  geoscientists to 
extract geological bodies from seismic volumes, such as reservoir 
bodies, salt bodies etc. In OpendTect, we have made some basic tools 
available for users to play around. So, if you want to make some bodies 
on  your application, this post might save you some time.

We have two kinds of bodies available in our code. One is 
MarchingCubes(wiki here <http://en.wikipedia.org/wiki/Marching_cubes>) 
based bodies, such as iso-surfaces. Another one is Delaunay triangulated 
bodies based on 3D points, such as polygon bodies, pick-set based 
bodies. But if you want to display seismic data on those bodies, you 
need to convert them into implicit bodies, which are implemented with 
MarchingCubes. Here, an implicit body is a  3D cube data set filled with 
-1, 0 1(or your threshold value with inside or outside values) and 
constructed by Marching cubes.

Here is a simple case of how to make and store your geo-body.

|CubeSampling body_range;  
/*Set this based on the required body boundary. */

mDeclareAndTryAlloc(Array3DImpl<float>*,arr,Array3DImpl<float> 
(cs.nrInl(),cs.nrCrl(),cs.nrZ()) ); 
/*The arr is what you really have to calculate. First, you have to make 
your geo-body either  by triangulation or by any boundaries you may 
apply.  After you have you body shape, you need to set all the position 
values based on your threshold, set negative value inside and positive 
value outside and 0 on the body boundary.*/

RefMan<EM::MarchingCubesSurface> emcs = new 
EM::MarchingCubesSurface(EM::EMM());
emcs->surface().setVolumeData( 0, 0, 0, *arr, 0, &taskrunner);
emcs->setInlSampling(SamplingData<int>(cs.hrg.start.inl,cs.hrg.step.inl));
emcs->setCrlSampling(SamplingData<int>(cs.hrg.start.crl,cs.hrg.step.crl));
emcs->setZSampling(SamplingData<float>(cs.zrg.start,cs.zrg.step));
emcs->setFullyLoaded( true );
emcs->setChangedFlag();
EM::EMM().addObject( emcs );
/*Now you may save the body the way you want.*/|

If you have any questions or suggestions on how to use or apply bodies, 
please let me know.

Happy coding.

Yuancheng

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