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:
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.

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