Figure 7 shows examples of various effects that can be achieved. At the top of the photo is a hologram of a deep plane of random stars with an opaque square floating in the foreground. At the bottom is a tetrahedron with one vertex penetrating the film plane and extending out into the air as a real image (the scratch radii decrease to zero, then increase again but with the scratches drawn upside down in order to produce a glowing real-image line.) To the left is a cylindrical distribution of random stars plotted by hand using trig tables. The cylinder also has a 3D curvy line extending above which was sketched entirely freehand with little effort. To the right is a 3D random starfield with a tiny galaxy in the center, complete with axial plasma streams. In the center is a square grid tilted in space (this grid was my first attempt at generating a fully 3D image rather than only creating flat image planes with constant depth.)
3.1 Speeding the production of arbitrary straight-line images
When generating virtual images composed entirely of straight lines (such as the edges of the above cube), a simple method exists which greatly speeds the process. First calculate the position and radii of the scratches that produce the endpoints of the glowing line. Scribe these scratches on the plastic. Next place the fulcrum point of your compass exactly midway along a line drawn through the two fulcrum points previously used to create the endpoint-scratches. Then set your compass radius so it generates a scratch that is positioned exactly midway between the two scratches forming the endpoints. Now scribe this "midpoint" scratch. Next, repeat the process of finding midpoints between the three existing scratches. You simply lay down the image points which divide the line into 1/2, 1/4, 1/8, 1/16, etc. The scratches resemble the markings on an English ruler, where new scratches are repeatedly placed between existing scratches. When the scratches are dense enough (say 1mm or 0.5mm apart) you're done. Observe the hologram under bright point source illumination and you'll see a glowing line connecting the two endpoints you initially calculated. Many additional hints and tricks can be found on my website [8].
3.2 Pseudoscopic images
In figures 3 through 5 the illumination comes from a source positioned vertically above the line-scatterer. If we instead illuminate the same scatterer from below, the scattered rays focus together rather than converging, and we obtain real images in front of the "film plane" rather than virtual images located behind it. If the "cube hologram" in figure 6 is illuminated from below, the cube is brightly visible and still maintains its general shape, but it turns inside-out and moves into the air in front of the plastic plate. It resembles the upper corner of a room rather than the projecting corner of a solid cube. In other words, using a conjugate illumination beam will change virtual images into real images, producing an effect that greatly resembles the pseudoscopic images of conventional holography. This probably explains why some of the images seen in car hoods appear to float in space above the abraded surface.