Lighting is the part of the technique that makes it work. Simply using reflection in a glass isn't enough to create the ghostly effects seen in our example. Lighting comes in 3 parts.

The Atmosphere

The tip here is that sunlight/moonlight should be deleted. This is so that there is not any spot light effect on the glass (which is essentially what sunlight is, a directional light). You can do this by cutting the Sun Light or Moon Light out of the object list.

Ambient lighting can be a good thing and it can create a certain color to your scene. It is wise, however, to use a dark atmosphere if possible and then make up any lighting with point lights, spotlights, etc. If the ambient lighting is creating unwanted light on your ghosts, then it may be necessary to shut it off.

The Solid Objects

The only rule for solid object lighting in Pepper's ghost is that you are careful not to shine the light on the glass. Point lights can be used, but be careful that they do not. The same holds true for a misplaced spot light (which should always point away from the glass). Again, making the glass completely invisible is the key.

While Pepper's ghost will work in well lit scenes, it's best to use it in darker scenes. After all, ghosts are frightfully sensitive to bright lights.

The Ghosted Objects

The ghosts reflect onto the glass depending on the intensity of the lighting upon them. A dim light will make a ghost more transparent, while a bright light will make it have more form.

Spotlights are used mainly in this because they are easy to control where the light is shining. You want them to be facing the ghostly figures, but such that the glass is not in the path of the light. Not to sound like a broken record, but we don't want anything to reflect on the glass, but our ghosts.

Using multi-color spotlights really can make a ghost seem eerier. For instance, a blue light will give him a scary ghoulish likeness.

Placing these lights and their intensities to get the effect you want is a matter of taste and would be hard for me to describe a scenario that would match your scene. Just practice with different settings and combinations to get the perfect ghost for your scene.

Other Lighting Considerations

The other thing to keep in mind is that if there is a particular strong light or direction of light in your solid scene, a spotlight should be used to simulate that on the ghost side {only less intense}. This is a matter of taste though as it depends on whether you want your ghosts to be effected by the general lighting.

Ghosts do not create shadows, and thusly they will not in Pepper's Ghost either. There may be ways around this, but I haven't come up with them yet. However, they will cast shadows on themselves and the other ghosts on that side of the glass (which will translate to transparent areas). This is something to keep in mind when placing lights.

Lighting softness can also give the appearance that the ghost is fading out rather than abruptness. This does require longer render times, but it may be worth it. Such lighting generally requires Ultra mode during render to work best.

STEP 5: THE BACKDROP

Okay, now you should be getting a reflection in the glass of your ghosts and the solid scene through the glass, but what is that annoying sky doing. Didn't ShadowWind tell us several times that nothing should be reflecting on the glass besides our ghost??? Yes, I did say that and that is why we have to cover the backdrop of the ghosts so that the sky doesn't show.

We do that by placing a cube (or a plane) in back of all the ghosts. We make this cube very large so that it covers the complete view of the camera. If you have a camera at an extreme angle, it might be wise to also put a box on both sides as well to keep any other light out. Depending on the angle, it may be necessary to also put a block box over the entire scene (as a roof) as well. The best way to look at this is to surround your ghosts in a room with black walls, floor, ceiling.

Do NOT place your scene inside a solid box to keep light out. Vue tends to do evil things with this and it does not work properly doing it this way.

APPENDIX A: ADDITIONAL NOTES:

Often you want the ghosts to be behind something, such as a table. You can do this by blocking out that part of the ghost by putting a black object (Flat Black material with 0 for Diffuse/Ambience/Lumious) in front of the ghost (on the ghost side of the glass) to keep the reflection of that portion from hitting the glass in the place you want.

Admittedly, this technique works best when ghosts are not behind complicated objects, because masking the ghost side to match (although it can be done) is difficult at best without postwork.

THANKS FOR READING THIS AND I HOPE IT WAS HELPFUL

And that's it, a quick and dirty how to for Pepper's Ghost. Hope you found it informative and look forward to seeing your own creations. And keep in mind that this isn't the only way, but just a basis for your own experimentation.

If you have any questions, feel free to contact me at ShadowWind@gate.net or IM ShadowWind on Renderosity.