Shadow Generator in Green Screen Wizard
GreenScreenWizard offers three shadow generators.
The Wall Shadow Generator
The Floor Shadow Generator
The Wall and Floor Shadow Generator
To activate any of the generators, simply decide on the type
of generator you would like and click on the appropriate button at the bottom
of the screen.
The Wall Shadow Generator
The wall shadowed generator gives, as the name implies, the
ability to produce shadows on a wall. The wall shadow generator is the simplest
to use and understand. It simply takes the green screen image and wherever
there is something solid it creates a black spot projected onto the wall. You
can move and scale the shadow using the top three controls shown.
You also have control as to how blurry and how dark the
shadow will be.
Here's the shadow with blur increased:
Here's the shadow with more transparency:
If your shadow has unwanted spots or if the hair or dark
areas are not showing up you may need to adjust the restore black slider. This
slider, like the slider in the combined page, will determine which blacks are
solid and which blacks are transparent. To remove the shadow simply uncheck the
"Add Shadow" checkbox or hit the "Clear" button.
The Floor Shadow Generator
The floor shadow generator is designed to place shadows on
the ground or floor. It is more complicated because people who are standing on
the ground want the shadow to start where their feet touch the ground. Because
GreenScreenWizard does not know where the person is standing you, the user,
must tell it.
Notice in this image, Carolyn seems to be floating above her
shadow. That is because the skew base, represented by the red line is not
aligned with her feet. We use the skew base slider to align the red line with
her feet, causing the shadow to be properly aligned.
Here is the image with the skew base in its proper position.
Notice how the shadow is now properly positioned now with her feet.
You can remove the red line by clicking "Clear Guides" or
by unchecking the "Show Baseline" checkbox.
Once you have the base defined, you can skew the shadow to
the left or the right using the skew slider.
You can also scale the shadow using the scale slider.
A problem arises if the feet in the photo are not parallel
to the base of the photo.
Consider this image:
As you can see we cannot move the baseline so that both feet
have the shadow at the right level. We can solve this problem in one of two
ways. We could move the feet off the screen as shown here. In this case we have
moved the shadow base below the bottom of screen.
A more complicated way to solve the problem is to use the
base angle. You adjust the skew base in the base angle until both feet are
touched by line. For bizarre mathematical reasons which I won't get into you
need to manually move the shadow into the proper position using the
right-and-left and up-and-down controls.
As with the wall shadow generator, you can use the shadow transparency and shadow border
controls. In addition to those feature, you may also want to use the show virtual room
function to make a more constant background for shadow adjustment.
The Wall and Floor Shadow Generator
The shadow generator that creates an image on the floor and
the wall is the most complicated. It will attempt to do a skewed image on the
ground until it hits the edge of the wall and then it will create a shadow on
the wall for the remainder of the image. To create this effect we need to give
the shadow generator two pieces of information. Like the floor shadow we need
to define the skew base to tell the shadow generator where the shadow should
start. In addition we need to define a virtual room to tell the shadow
generator where the floor ends the wall starts. This is probably best shown by
example.
Let's start with this image. As you can see there is some
floor and some wall, in this case curtains.
Clicking the wall and floor button will cause the following
image will appear.
The red line is the skew base that needs to be lowered to
below her feet. The light gray area shown is the wall of the virtual room. The
dark gray area is the floor. We can adjust this dividing line with the virtual
room left edge and the virtual room right edge sliders. In this case we need to
lower the virtual room slightly tilted to match the curtains.
After we adjust the virtual room to match the line of the
curtains we can adjust the scale and the skew in the skew base to give us a
realistic shadow.
We then click the "Clear Guides" button to remove the virtual room and
if present, the skew baseline.
Closing the dialog will cause the Wizard to compute the
final output as shown here.
The shadow generator only works on things that are
visible on the screen. It also assumes a flat background, one that does not
have any holes like a window.
If used properly the shadow generator can add realism to
your green screen photography.
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