In this example the active layer is number 7 (boundary is yellow). A layer is made active by either clicking the middle mouse button with the layer, or by typing in [u] or [d] on top of the graphics window to select the next highest (up) ar lowest (down) layer. A node has been selected (white square) by clicking near the node. When selected, the parameter values of the node are displayed in buttons to the right of the model. In this case, for a boundary node, the X-location (153.59 km), the depth (34.55 km) and the inversion switch setting are displayed. These values can be edited by moving the cursor over top of the value (or using the [Tab] key automatically move the cursor over to the buttons) and typing in the new value, followed by a [return]. As each new value is typed in, the location of the node is updated. Also if the node location is move with the mouse, the parameter values in the buttons at the right are automatically updated.
At the bottom right of the model the currently selected layer (7) and the number of boundary nodes and upper (v1) and lower (v2) velocity nodes are displayed. These values are constantly updated as nodes are added or deleted. To delete a node one merely places the cursor near a node and hits [ctrl-x]. If a node is selected (white) hitting [ctrl-x] will delete it regardless of how close the cursor is to the node.
To edit depth (boundary) nodes, one types in [n] on top of the graphics window. This displays the nodes for the selected layer. Typing in [n] again (or [Esc]) hides the nodes. Similarly, typing in [V] or [v] toggles the upper or lower velocity nodes respectively. Depth and velocity nodes cannot be edited simultaneously, but both upper and lower velocity nodes can be edited simultaneously.
In the above example, we have zoomed in to the upper 10.8 km of the model. Layer 4 has been selected. Typing in [ctrl-a] on the graphics window selects all of the nodes (white squares), and draws a new set of buttons to the right of the model (labeled "Change all"). One can move the entire boundary by either clicking with the right mouse button to relocate the boundary, or type in a shift in the "dZ" box (in this case a 2.0 km shift was entered and the boundary was moved down). A negative number would shift the boundary up. Entering a number in the "Z" box would result in all of the nodes being assigned a constant velocity. Also, the inversion switch of all nodes can be set to 0, 1 or -1 by typing in the third button (or clicking with the mouse to toggle between 0, 1 and -1). Note that when a boundary is moved this way, it is possible to end up with crossing boundaries.
Similarly, when velocity nodes are displayed, typing in [ctrl-a] allows you to set the velocity of all nodes to a constant value, or to shift the velocity of all nodes by a constant value, or to set the inversion switch of all nodes.
Example of creating a pinchout. Typing in [p] on the graphics window enters pinchout mode. Four new buttons appear at right. The part of the boundary to be pinched out is entered in X1 and X2 boxes. Or, alternatively as demonstrated here, one can click the left button and then drag a (yellow) box to select a portion of the active layer to be pinched. (Only the horizontal extent of the "rubberband box" is important. The box doesn't even need to include the active layer.) The part of the boundary to be pinched is highlighted in grey. The numbers in the X1 and X2 boxes are updated after selecting with the "rubberband" box. The layer can either be pinched up or down. In this case "down" has been selected. Clicking on the "Pinchout" button, or simply hitting the [spacebar] on top of the graphics screen perfoms the pinchout, as shown below.
