Creating
a Custom Drop Shadow Tool
In this lesson,
you will create a drop shadow using an existing clip as a starting
point. This will involve some color correction, blurring and translation.
At the end, you will turn the drop shadow operators into a subnet
and publish it as a Digital
Asset. This will make it easy to re-use in future composites.
This lesson
will continue from where the Layering
Clips lesson finished. You can load the following file to give
you a clear starting point.
If necessary,
select Network > Compositing
(SOP) from the Viewer pane menu. Press i
to go into img1.
1.
Add a Transform COP
In the Network
pane, MMB-click
on the output of the butterfly operator and select
Effects > Transform
then click to place.
This operator
is branching away from the original node. Click on the output of
the xform COP and then click on the input of the
layer COP. In the Parameter pane, move the
xform operator up on the list so that it sits above
butterfly. This means that it will be below butterfly
in the composite.
2.
Create the Shadow Effect
Select the xform
operator and in the Parameter pane, set the Translate
values to 0.025
and -0.025.
These values are UV values as opposed to pixel values. The new butterfly
is appearing from underneath the original.
RMB-click
on the output of the xform operator and select Color
> HSV then click to place. This operator
is placed between the existing operators. Select
the new hsv operator and click on the A
button next to Plane Scope
to focus the color shift on the RGB channels and not the Alpha channel.
Next, set Saturation
Shift to 1
and Value Scale
to 0. Now the
shadow looks black.
3.
Blur the Effect
RMB-click
on the output of the xform operator and select Effects
> Blur then click to place. This operator
is placed between the existing operators. Select the new blur
operator and set its Size
to 35. Now the
shadow has a softer look.

4.
Make the Shadow Opacity
RMB-click
on the output of the blur COP and select Color
> Bright. This inserts a Bright
COP in-between this operator and the layer operator.
In the Parameter
pane, set the Plane Scope
to A (alpha)
by clicking on the R, G and B buttons to turn them off. This will
make sure that the brightness setting is only affecting the incoming
alpha.
Set Brightness
to 0.66. The
shadow is now semi-transparent. You can use this value to control
the opacity of the shadow.

5.
Create a Subnet
In the Network
pane, select the four operators contributing to the drop shadow.
Press Ctrl-RMB
and select Collapse Selected into
Subnet. Rename it drop_shadow.

6.
Create a Custom Operator Type
RMB-click on
the drop_shadow subnet and select Create
Type From... Set the Operator
Name to drop_shadow and the
Operator Label
to Drop Shadow. Set the Save
to Library to $HOME/houdini6/OPcomposite.otl
and click Accept.
In the Operator
Type Properties panel, click on the Parameters tab. In the Network
pane, go into the drop_shadow subnet and select
the xform operator. From the Parameter pane, drag
the Translate parameter name onto the Parameter list in the Operator
Type Properties panel. Set its Label
to Offset.
Next, click
on the blur operator and drag the Size
parameter name onto the Parameter list. Set its Label
to Blur Size.
Next, click
on the bright operator and drag the Brigntness
parameter name onto the Parameter list. Set its Name
to opacity and its Label
to Opacity.
Click Accept.
Click on the drop_shadow operator and the new parameters are available
for editing.

7.
Test the new tool
In the Network
pane, MMB-click
on the output of title and select Drop
Shadow. Click to place a new branch that uses
the drop_shadow operator. Re-link this into the
layer operator and position it under the title
on the list. If you want, change some of the drop_shadow
parameters to control the shadow.

8.
Render out the Results
In the Network
pane, select Network > Outputs.
Press tab > Generators > Composite.
In the Parameter pane, set the COP name to layer1
then click the Render
button to render to an mplay window. You can also set up the
Output Picture to render out a sequence of images.

Re-using
the Drop Shadow tool
When you created
the Drop Shadow
tool, it was put into the OPcomposite.otl
Library and referenced into your Houdini (hip) file. When you start
a new file this tool is no longer available. To access it, you must
install the OPcomposite.otl
Library using File > Install
Operator Type Library...
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