shift of volumes between scenes

[Brian Brennan]

Good afternoon all.

I just encountered a problem using OpendTect (free version, I think it was 7.0.4) and I wondered if it is a known issue, user error, or something else. Here is what happened:

I have done quite a bit of work in the project in question and had verified that the data was in the right place and indexed properly in time. I had several objects visible in Scene 1, including a co-blended z slice, some wells, and so on.

- I created a Scene 2, and into it I loaded a subvolume volume I created from an existing volume by grabbing the data between two horizons. 

- I loaded that volume into the second scene and made all but the anomalies transparent. Looked great and showed exactly what I needed to show. 

- But when I loaded a dummy well into one of the anomaly blobs using x and y coordinates from the original dataset from my other interpretation software, it showed up exactly as it should have in Scene 1 going through the heart of the anomaly blob, but it didn't hit the blob in Scene 2. The entire volume seemed to have shifted. When I put the cursor in Scene 1 and saw where it was in Scene 2, the events didn't match up. 

- When I load a Z slice into Scene 2 it lines up properly. Seems to be a problem only with the sub-volume.

Thanks for any help you can give me.

Regards,

--

Brian Brennan

Geophysicist

337-258-3641

email: BrianDB...@gmail.com

website: Third Wave Geophysics.com

[Hesham Refayee]

Hello Brian,

Could you please load your subvolume into Scene 1 and check its alignment against your original cube and compare that to scene 2?

Regards,

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Hesham Refayee

Senior Geoscientist

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences

Phone: +12812403939 E-mail: hesham....@dgbes.com Internet: dgbes.com

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[Jonny G Pinto]

Don't know much about OpendTect, but try creating the sub volume using a time reference interval that will include both horizons, then make sure that when loading the sub volume it is loaded at the right time. 

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From: Brian Brennan <briandb...@gmail.com>
Sent: Wednesday, October 22, 2025 1:43 PM
To: us...@opendtect.org <us...@opendtect.org>
Subject: [OpendTect_Users] shift of volumes between scenes

 

[Paul de Groot]

Hi Brian,

I can't reproduce this bug in v7.10. I added a 2nd scene and added volume viewers with default seismic to both scenes. The viewers were aligned perfectly.

Best regards,

Paul.

--

Paul de Groot

Special Adviser

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences
Phone: +31 53 4315155 E-mail: paul.d...@dgbes.com Internet: dgbes.com

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[Brian Brennan]

A little more on this:

I've upgraded to 7.0.9.

I recreated the sub-volume since I first noticed the problem.

I loaded the volume into Scene 1.

The sub-volume was created using the same horizon, top = horizon +50 ms, bottom = horizon + 250 ms.

Problem still exists. 

Pictures below show

1) z slice through anomaly

2) partly transparent volume showing high amplitude anomalies 

3) both

All are shown directly from above, with no tilt. Maybe hard to tell from still pictures, but hopefully you can see in picture 3 that the events are offset from one another.

(the prominent event at the bottom on the volume pictures is at a different time than the one at the top, so the z slice doesn't see it)

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[Paul de Groot]

Hi Brian,

I assume that with no tilt, you mean that perspective view is toggled off. Secondly, I assume that the time-slice and the volume viewer both display data from the same sub-volume. If so, I do not understand why these images are not displayed on top of each other. To investigate this, would it be possible to get access to the sub-volume? (Ideally in a backup of the OpendTect project with only the sub-volume present.)

Thanks and best regards,

Paul.

--

Paul de Groot

Special Adviser

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences
Phone: +31 53 4315155 E-mail: paul.d...@dgbes.com Internet: dgbes.com

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[Brian Brennan]

Hello Paul.

By no tilt, I mean that the view is directly from above, looking straight down on the volume, so there is no parallax, if that is the proper term. And yes, perspective is off.

But they aren't from the same volume. The time slice is from the original volume, and the sub-volume is a separate volume extracted from the original. So I'd guess that a backup would have to have both. 

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[Brian Brennan]

In fact, when I select a time slice from the sub-volume it looks just like the slice from the original volume. In other words, it doesn't match the volume.

I'm looking at the documentation to figure out how to create a copy of my project. Is it a matter of just making a copy of the project folder? If I can do that I'll get rid of everything but the subvolume and send it to you.

[Paul de Groot]

Hi Brian,

If they are not from the same volume, I suspect that something went wrong in the creation of your sub-volume. To test whether the original volume differs from the sub-volume, or something is wrong with the volume viewer (which I now doubt) I suggest to compare the following displays:

1. Display a Time-slice at position Z showing the original volume
2. Display a Time-slice at position Z showing the sub-volume using the same display settings (non-transparent color bar and same clipping). Are 1 and 2 the same? If not, the sub-volume differs from the original data.
3. Add a volume viewer showing the sub-volume. Use the Display -> Position menu to show the same Z position as above. Use the same display settings (not transparent). Is the Z-slice the same as under 2? In that case, there is nothing wrong with the volume viewer.

Best regards,

Paul.

--

Paul de Groot

Special Adviser

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences
Phone: +31 53 4315155 E-mail: paul.d...@dgbes.com Internet: dgbes.com

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[Paul de Groot]

Our mails crossed. I see that you already partly did what I suggested. You can copy a survey in the survey setup window using the copy icon in that window. Please send it to paul.d...@dgbes.com.

Best regards,

Paul.

--

Paul de Groot

Special Adviser

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences
Phone: +31 53 4315155 E-mail: paul.d...@dgbes.com Internet: dgbes.com

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[Brian Brennan]

Aha! Here is what is happening.

In perspective mode, all is good. In orthographic mode, however, I get the apparent shift.

Maybe I have misunderstood how this should work. I figured if I was in orthographic mode, which I use a lot because it looks like a 2D map when you look directly down from above, things should line up. But it seems not to work that way.

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