User Guide > Modeling > Techiques   

Editing Points on a Surface

To edit a surface you can use an Edit surface operator (SOP). This tool lets you pick points then manipulate them in 3D. You can repeat these steps with different selections of points all within a single Edit SOP. This differs from many modeling operators which allow you to only apply an operation to one selection at a time.


1. Create a Grid

Select File > New and save any work that you want to keep. Click the following button to have Houdini build the grid for you:

Load Start File

In the Viewer pane, tumble the view to see the new ground grid. Select View > Shading > Smooth Wire Shaded to see the edges of the polygons. Select the ground object in the Network pane, and press i to go into this object.

2. Apply the Edit SOP to some Points

In the Viewer pane, press tab > Filter > Edit. From the Viewer Pane menu, select Select > Selection Type > Points to choose this method of picking. At first you can't see any points. Click on the stowbar at the right edge of the Viewer pane to bring up the Display option bar. Click on the Points button to make the surface points visible.

Shift-click on four or five points at various points around the perimeter of the grid. RMB-click to accept these points and start editing. Click-drag up on the vertical handle on the transform manipulator. This moves the points up to create small peaks.

Note: Make sure that Select > Select Whole Geometry is off so that you can focus on individual points. If all points are selected with one click then Select Whole Geometry is probably on.

3. Soften the Points

The edited points create a harsh result and could use some softening. MMB-drag in the Viewer pane to call up a value grid which lets you adjust the edit operations Soft Radius. This creates a drop off for the point edit. You could also adjust the Soft Radius slider found in the Operation controls at the top of the Viewer pane to achieve the same results.

4. Manipulate Another Point

Right now your point selection is locked to the five points you have already selected. To create a new selection you can choose Select > Reselet Geometry from the Viewer pane menu. This puts you into a selection state where you can either replace, add or remove from the selection you already have. There are options in the Select menu for these three approaches to selecting.

Click on one or more points on the surface then RMB-click to accept. Now you can edit this point using the transform handle. To control the handle itself, RMB-click on the handle to pull up a menu of options. For instance, you can change the handle to a Rotate (r) handle or use the Peak Handle (y) to work off normal to the surface.

5. Disable Secure Selection

If you do not want to choose Reselect Geometry every time you want to select new points then you can toggle Select > Secure Selection to off. This means that any click that is not on the manipulator directly will start a new selection. As usual, any new selection would require a RMB-click to accept. Some people will find this a faster way to work while others may not want to take a chance that their existing selection is not accidentally lost - (although any selection change can be undone using Edit > Undo)

6. Selection Style

You may also want to change your Selection Style which can be set using the Viewer pane's Select menu. You can choose either Box, Lasso or Brush selection. The Lasso selection is shown below.