[OpendTect_Developers] Help with Fault creation in 3D Seismic Image

[Bert Bril]

Hi all,


Jaideep Singh wrote:


> Yes, I want to be create a fault in a 3D surface with the fault
> properties like length in X, Y and Z provided.

Your explanations are pretty vague. Especially software developers hate 
vague specifications ...


> Other thing I want to do is change values of seismic volume around a
> seed point.

This will be *hard*. You cannot, in OpendTect, edit stored seismic data 
in-place. To change it, you will have to create a new line attribute 
(2D) or a new cube (3D). It's not easy at all, you may want to take the 
Browse/Edit functionality in the seismic data manager as an example 
(uiSeis/uiseisbrowser.cc).


> For this, I want to enter seed point coordinates ( which
> would be in X, Y, Z ?).

In OpendTect, coordinates are X, Y and some kind of Z (depending on 
where you are looking). In general, Z will be the survey's Z dimension, 
which can be time or depth, time in seconds and depth in meters or feet.


> If I enter these in X,, Y, Z, what relation does
> this have in the attribute nextStep() function that is called for every
> trace.

 From this I conclude that you decided to use the Attribute Engine to 
access your data. I'm not sure whether this is the right choice. I would 
make the choice based on whether you want to extract attributes.

If you look in the Tutorial plugin, you'll see that you can also access 
seismic data as such, directly.


> *I'm not sure how to relate X, Y, Z to samples in traces*.

You need to find the trace that contains that sample. There is no 
universal (X,Y,Z) -> sample value function. This is because seismic data 
is usually not accessed in this way, but rather in bundles of traces or 
trace parts. You figure out at what positions you need the traces, and 
then receive them in the order that suits the provider.

If you use the 'direct access' methods, you'll likely use the 
SeisTrcReader combined with a Seis::RangeSelData object:

* For 2D seismics, you'll need to search for this (X,Y) along the line. 
If you happen to know the trace number, life will be a lot easier. The 
searching can be done in the 2D line geometry database S2DPOS().

* For 3D seismics, convert the (X,Y) to inline/crossline using 
SI().transform().

Setting the RangeSelData will make the reader only deliver the one trace 
you want. The needed sample value is trivial to get unless the Z 
dimension of the trace is not the one you need.


> Also, in place of entering seed point, I want to just left-click mouse
> button to achieve this. How can this be done?

Not really my field of expertise, but you have to beware of the fact 
that different scenes can have different vertical axes. For example you 
can have depth scenes in time surveys. Or even some other dimension, 
like geological time.



Bert

-- 
-- Bert Bril / OpendTect developer at dGB
-- mailto:Bert.Bril at opendtect.org , http://opendtect.org