Description

Velocity Brush Editor is an interactive tool for manually retouching a velocity model that is displayed as a 2D section (trace position versus depth). Instead of editing numbers in a grid, you click and drag a round or elliptical "brush" cursor directly over the velocity section in the viewer to locally raise, lower, or replace velocity values, much like a paint tool in an image editor. The size of the brush is set simply by how far you drag when you click, so no separate brush-size control is needed. This makes it quick to smooth out picking artifacts, fix a localized velocity bust, or blend in a known velocity near a well without leaving the interactive view. Every stroke is recorded, and pressing Ctrl+Z undoes the last up to five strokes, so edits can be tried out safely before the result is accepted.

Input data

Input gather

The velocity gather to be edited, arranged as trace position along one axis and depth along the other. This is the model you loaded for review (for example, a velocity field produced by tomography, NMO picking, or a previous depth-conversion step). The module never changes this input directly — it is kept untouched so that the "Max relative change" limit and the "Relative" brush mode always measure against the original, unedited values.

Parameters

Work mode

Chooses how the brush changes velocity values under the cursor. Relative nudges the existing values up or down by a percentage each time you paint over them, which is useful when you simply want an area to be "a bit faster" or "a bit slower" without knowing the exact number. Constant instead blends the painted area toward a single target velocity that you specify, which is useful when you know the correct velocity for a zone (for example from well control or a known lithology) and want to force the model toward that value. Switching this option changes which of the other parameters are shown, since "Brush percentage" and "Max relative change" only apply to Relative mode, while "Desired velocity" only applies to Constant mode.

Default: Relative. Start in this mode for general smoothing/nudging work, and switch to Constant only when you have a specific target velocity in mind for a given area.

Brush percentage (+ increase, - decrease)

Only used in Relative work mode. Sets how strongly each brush pass changes the velocity under the cursor, expressed as a percentage of the current value. A positive value raises velocity where you paint; a negative value lowers it. The full percentage is applied at the center of the brush and fades toward the edge (the fade shape is controlled by "Harshness"), so a single pass rarely swings the whole footprint by the full amount at once — repeated strokes over the same spot build up the effect (subject to the "Max relative change" limit).

Default: 0.1 (10%). Use small values (a few percent) for gentle, cumulative touch-ups you build up with several strokes, and larger values when you need a fast, more aggressive correction in one or two passes.

Max relative change

Only used in Relative work mode. Caps how far any single point of the velocity model is allowed to drift from its original (unedited) value, expressed as a percentage. No matter how many times you paint over the same spot, the resulting velocity is always clamped to stay within this percentage above or below the value it had before you started editing. This acts as a safety limit that keeps repeated brushing from producing unrealistic velocities.

Default: 0.2 (20%), minimum 0. Lower this to keep edits conservative and close to the original model; raise it if you need to make larger corrections and are confident the change is geologically justified.

Desired velocity

Only used in Constant work mode. Sets the target velocity value that the brush paints toward. Near the center of the brush, the painted value moves closer to this target; toward the edge of the brush the effect fades and the original value is preserved, giving a smooth blend rather than a hard-edged patch. The on-screen brush cursor is color-coded to this value while Constant mode is active, so you can see at a glance what velocity you are about to paint.

Default: 2000 m/s, adjustable from 0 to 20000 m/s in steps of 100 m/s. Set this to the velocity you expect for the layer or feature you are correcting, for example a value tied to well control or a known lithology, before you start painting.

Harshness (0=soft, 1=hard)

Controls how sharply the brush effect is bounded, independent of work mode. At 0 the brush is fully soft: the change is strongest at the center and fades smoothly and gradually to nothing at the edge, so edits blend seamlessly into the surrounding, unpainted velocities. At 1 the brush is fully hard: the full effect is applied uniformly everywhere inside the brush footprint with no feathering, producing a sharply bounded patch. Values in between give a progressively narrower, steeper falloff as you move from soft toward hard.

Default: 0.1 (mostly soft), adjustable from 0 to 1. Keep this low for natural-looking, blended corrections; raise it toward 1 when you need to stamp in a well-defined value over a specific zone with a crisp boundary.

Output data

Output gather

A copy of the input velocity gather that carries your manual brush edits. It starts out identical to the input gather and is updated live in the viewer as you paint, so you can see the effect of each stroke immediately. This edited gather is what should be carried forward into any downstream step, such as depth conversion or migration, once you are satisfied with the touch-ups.