Once velocity picks have been made they can be gridded using the volume processing tools. The VMB plugins contains a special tree item that enables a quick application of the volume processing workflow without the need to process the entire volume:
Pressing "Add velocity display" in the right-click menu of a slice (inline, crossline, time-slice) adds a special layer. Its right-click menu does not allow the selection of stored volumes or attributes, but the selection of a stored volume processing (gridding) flow.
The selection of a flow will launch its computation on the current slice only. If you already added a velocity display ,you can either reload it in case of modification or select a different processing setup.
Note: Although the display is for a single slice the computation is still volume-based. Therefore it can take some time to process and will make OpendTect unresponsive during that period of time. For large jobs batch processes may still be preferred.
The volume processing tool of OpendTect has a step called "Velocity gridder". It can grid either velocity functions or volumes.
The VMB plugin enables the selection of a third velocity source, the velocity picks made in the VMB analysis windows (vertical/horizontal). No parameter is required since the velocity picks are attached to the migration velocity during the analysis. The stored RMO will be converted to interval velocities and gridded in the volume. Please note that the gridding of velocities is done in order to maintain the time-depth relation hold by the velocity function.
The surface limited filler intends to paint velocities in a 3D area whose geometry is defined by one or more 3D horizons. This step may look like the inter-horizon filler but it is actually more powerful.
The Add and Remove buttons should be used to select the 3D horizons to be used in the actual step. The side defines the relative position of the horizon with respect to the area to be painted with velocities. For instance one of the horizon could be a salt flank loaded as a 3D horizon.
The painted velocities are referenced to a specific time. This time can be either constant (user-defined), or retrieved from a 3D horizon and not necessarily from one of the horizons defining the limit of the body. An horizon in between could for instance be used.
Then velocities are painted from that reference time. The velocity must be provided as a velocity/gradient pair. The values are once again either user-defined or extracted from a surface data (grid) attached to a 3D horizon.
