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         Tutorial 4: Advanced Shadowing

         Gaffer has added the ability to add realistic shadows to your
         scene. The soft edges of these shadows are not simple blurs like
         shadow maps can give, but the true shadowing effect due to
         partial blocking of area lights. Shadows in LightWave are an
         expensive option (in rendering time), and these area light
         shadows are even more expensive. However, Gaffer gives you this
         new ability as an option allowing you to optimize the look of
         your scene as you feel best.

         We'll go back to the urn scene we've been using for our tests and
         see how we can change the shadows the urn casts onto the ground.

         Load "arealght.lws". The urn's surface is the same as before,
         with selective lighting used to ignore the fill lights. We want
         the ground surface to receive the area light shadows, so go to
         the ground surface, and open Gaffer's options panel. We want the
         main light to cast these area light shadows.

         We do this by typing the light's name ("Main") in the first
         "Prefix" field in the "Area Light Shadows" section of the panel (
         not the Light Intensity Adjustments section.) You should a "1"
         beside the entry letting you know that there is one light in the
         scene that matches that prefix.

         Area lights cast soft shadows because they have a finite size, so
         we need to define that size. We also need to tell Gaffer a
         quality setting for the shadows. A higher quality makes more
         accurate shadows, but takes longer to render.

         For testing purposes let's try a "Quality" value of 10% and a
         "Radius" of .3. Usually you keep the quality setting very low
         when you are testing, then set it to a final high value for final
         rendering. Render the frame and you'll see the effect of this
         area light.

         Obviously the radius setting is to high. The shadow is very
         broad, and has speckles in it due to the low quality setting. We
         can make the shadow smoother by raising the quality, but render
         times will increase, so you usually have to compromise based on
         your needs.

         Let's fix our shadow by reducing the light size and making
         tighter shadows. This will incidentally increase the shadow
         quality (at no extra render expense) because tight shadows are
         more efficient than "loose" ones. Go back to the ground surface's
         Gaffer settings, change the light radius to .05, and render a
         frame.

         Now the shadow shape is looking good, but we need to decide what
         quality setting to use. The setting you choose is up to you, and
         is based on your machine speed and personal patience. Here are
         some settings to try, along with the render times on a 200 MHz
         Pentium Pro.Try these to get a feel for the quality you can
         expect from mixing and matching quality settings with AA
         settings.

         10% Quality - Medium AA - 2 minutes 22 seconds
         50% Quality - Medium AA - 4 minutes 12 seconds
         100% Quality- Low AA - 3 minutes 41 seconds

         When choosing area light qualities, remember that LightWave's own
         antialiasing helps considerably. One common mistake is deciding
         the shadow quality settings on a scene that uses no antialiasing,
         then rendering your final scene with AA turned on. This
         effectively uses settings that are too high, and therefore too
         slow.

         Judging from the three render tests, a good compromise quality
         setting would be using Low AA and 100% shadow quality. One
         advanced trick that can be useful is to use LightWave's "Surface
         Blur" plug-in, or even the Bloom tool (which comes with Gaffer!)
         to fuzz the shadows slightly by simply blurring the surface
         itself.


