SECTION 8 - Essence Settings and Other Attributes

13] Spaceship shield, By Charles Blaquiere (Essence)

To do a Star Trek-like "shield absorbs energy blast and dissipates it", you need to create a sphere for the shield. You then use Shellturb combined with SwapCRF to _vary the transparency_ of the texture and make the energy blast visible. Here's an example:

Create a standard Imagine sphere. Scale in Z by 0.5.
Give it a color of 255, 255, 255 and click on Bright. Add the Bandturb (not Shellturb) texture.

Edit the texture as follows:

  Column One     Two
         0       0.4          Axis position: 110, 0, 0
        20       0.4          Alignment: 0, -90, 0
        30       0
        20       0
        10       0
         5       0
         4       0
         0.4     0

Add the SwapCRF texture. All parameters should be 0, except Color -> N Filt which should be 1.
Add the Solid texture. Leave all parameters at -1 and set Color to 50, 255, 200.
The texture order should read, from top to bottom: Bandturb, SwapCRF, Solid. If not, use the Priority button to make it so.
States/Create DEFAULT, click Textures/Brushes on.
States/Create START, click Textures/Brushes on (This is not a typo. Unless I'm mistaken, you should refrain from using the default state in an animation, which is why I had you create an identical state).
Change the texture:
Time to 1
Fade to 1
Position to -50, 0, 0
States/Create END.
In Action, morph from START to END over N frames.

You'll see an energy blast hit the right side of the image, where the ship inside the shield would presumably be pointing, and travel along the shield, dissipating as it goes along.

How does it work?

The base object is white, and gets a turbulent band of black applied to it using Bandturb. Then, SwapCRF turns this color information into _filter_ values -- black means no filter, white means fully transparent. This makes part of the shield visible. All that's needed is to give the visible parta of shield a color using Solid. Finally, we create two states, START and END, which allow the texture axis to travel from one end of the shield to the other. The END state also has Bandturb's Fade parameter set all the way to 1, so that the texture loses strength as it travels along the shield. Just add a ship inside the shield, and a starfield in the background. The effect is beautiful.

**BUG ALERT**
Imagine 3.1 doesn't remember texture parameters and axis settings very well when you use States. Until that bug is fixed, you will need to create two separate objects, Shield-start and shield-end, and morph from one object to the next. No big deal.

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