Monday, August 31, 2015

Putting the Rainbow into Rainbow Caverns

Rainbow Caverns on the TMMC is being modeled as three major show scenes: A bat cave filled with glowing eyes, colorful Rainbow Falls, and a beautiful grotto of color changing crystals. Major work has been completed on the central Rainbow Falls scene and that's the topic of today's post and video log.

Most scenery and effects work is now complete on the upper section of Rainbow Falls, a major scene within Rainbow Caverns, and I'm excited to share the results today in a new post and video log. Tried and true "illusioneering" and stagecraft was used to bring this scene to life with a major element being the "Pepper's Ghost" rainbow effect in front of the falls. Check out this month's video log for a rundown on how the scene was created, and follow along with the photo's below for a more in-depth explanation.

Thunder Mesa Video Log: August 2015

Some representation of Rainbow Caverns has been part of the plan for Thunder Mesa from the very beginning. In fact, it goes back even further, starting with early plans to model Nature's Wonderland, and then on to my HO and On30 Big Thunder & Western layouts. At long last I'm getting around to the real magic at the heart of this model railroad and having a wonderful time playing with miniature versions of some of those classic Disney effects. The Rainbow Falls scene is achieved with a combination of ultra-violet light effects and the classic Pepper's Ghost illusion.

A Pepper's Ghost Rainbow

The waterfall is made from clear acrylic, painted on the back with transparent blue UV reactive paint. The "floating" rainbow is a Pepper's Ghost illusion - basically, a view-point controlled glass reflection.

The Pepper's Ghost illusion is used to make semi-translucent objects appear to float in mid-air. In reality, it's the exact same effect you see when you look at your own reflection in a window. Here, however, the viewing angle is tightly controlled so that only the illuminated object, in this case a photo of a rainbow, can be seen in the reflection. If you've ever experienced the Haunted Mansion at a Disney park then you have seen expert use of this classic illusion. 

Here, a simple black box has been created from cardstock with a blurry rainbow printed against black glued inside. An improvement on this design would be to curve the image around the inside of the box so that no edges will be reflected. My second version (not pictured) does just that.

To illuminate the rainbow, a single white 3mm LED was installed in this faux rock fixture.

The next step in creating the illusion is to position a piece of glass at an angle to reflect the picture or object but not the viewer. Note the the glass should be the full height of the scene. In this case, that's five inches.


All of the rockwork inside the caverns is made from pink polystyrene foam. Some are like set pieces, and are removable for maintenance. Layers of these set pieces are positioned to hide lighting rigs, and to complete the illusion of depth in the caverns when viewed from the proper angles. This is Stair Case Falls under UV light.

Here a piece of polystyrene foam is being shaped with a cone sanding bit in a Dremel tool. This goes fast but you have to be careful not to sand away too much!

Each piece is then painted flat black. Once that dries, varies purples and blues are dry-brushed on for a mottled appearance. Keeping the rocks a dark blueish gray helps to make the UV painted objects pop and makes the caverns seem darker, larger, and more mysterious than they are.

The Waterfall

The waterfall was created in the same basic way as the waterfalls for Big Thunder Creek, by sculpting 1mm thick clear acrylic sheet with a hot soldering iron.

The acrylic waterfall was then painted on the back with blue transparent UV paint before being cemented in place on its own set piece with clear silicone caulk.

A single 5mm UV LED is hidden behind the falls for illumination.

UV Lighting

Several of these 5mm Ultra Violet LEDs were positioned strategically in the scene for added illumination. Outside the waterfall, the creek itself is nothing but acrylic UV paint and gloss medium. Here you cam also see the 12v wiring buss that runs below the caverns from a DC transformer. The red wire is positive and the black is negative - important to know when working with LEDs.

I needed a simple way to mount LEDs to the roof of the scene and still have them be flexible enough to aim the lights. Cheep plastic bendy straws came to the rescue. Painted flat black and attached to the ceiling with a dab of hot glue, they make for quite serviceable miniature lighting rigs. A scrim of rockwork hides rigs like this from view.

What's Next?

Down below Rainbow Falls where the track crosses the creek on a stone bridge, there will be a series of deep pools, each slowly changing color as the magical waters drip down from above. Beyond the falls will be a Crystal Grotto, dancing with light. And let's not forget the Bat Cave with its hundreds of shining eyes. Yes, there's much more to come in Rainbow Caverns! But that will have to do it for this time. Thanks for checking in, Amigos. Adios for now!

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