I had wanted to make some kind of sphere that pops out of the screen for a while, but couldn't quite decide how to fake it or otherwise actually do "for real" in UF. Then Gilles Nadeau posted a UPR to the Ultrafractal list a while ago where he had assembeled a cube by projecting a hyper-barnsley into 3d-space and then raytracing it to make a 2d image. What you see here is an extension of that: a 4D version of a gnarl is projected into 3d-space and then raytraced to make a 2d-image. However the raytracer is run in three layers to generate the red, green and blue channels independently with a 3 degree offset for the red channel. You'll need red/blue (better: red/cyan) glasses for this one, with red on the left (I think that is the ususal arrangement). Since the relative distance of the raytracer from the "object" was set at 6, the effect should be best if your distance from the object is about 3 to 4 times its diameter. (For an added gimmick, try flipping your glasses so that red is to the right -- you should now see the ball as an indentation into the screen). The only thing I added after UF finished rendering is my name - there's no other "post-processing". I'm indebted to many people on this one; in particular Reg Atkins for getting me thinking about the concept and Gilles Nadeau for giving me the idea. And Cliff Pickover (I think) for the Gnarl algoritm. (Note: If I understand this right, then this is not a 'quartic' gnarl, merely your run-of-the-mill 2D-gnarl with quaternions substituted for complex numbers. It is "4D" in the best sense, but doesn't really exploit any of the things one could do in 4d that are impossible in 3D)