FractalWorks

This no longer "Free": now only available from the AppStore, it goes for $9.99.

Nice app overall and on my 2.66 Ghz Mac Pro 1,1 with an NVidia 8800 GT graphics card running OS 10.6.8 it is very fast so I would imagine no speed problems on newer systems. The navigation, 3D view manipulation and anaglyph capabilities are all easy to comprehend but fairly basic. The color scheme editor is rather bizarre and not intuitive. You'll need to use it too, because many of the provided palettes aren't very pleasing. No palette rotation or creation of animations unfortunately. Images always seem a bit spotty and ragged because of lack of antialiasing except in the 3rd dimension. The window size systems and constraints are handled oddly as are a few other UI elements including menus. My primary reason for giving it only 3 stars is it's inability to work with any fractals but a basic mandelbrot or associated julia, which makes for pretty similar images. No variation in equations and no interesting operations on the fractals other than making them into 3D views. No orbit traps, self-squared dragons, attraction basins, periodicity analyses, binary decompositions or what have you to add interesting variations to the results. Needs something besides anaglyph capability to give images unique appearance from every other such app! Also, Like most anaglyph creating apps I've seen, it provides no way to fine-tune the colors to optimize them for particular anaglyph glasses, leaving alteration of a monitor's color settings as the only option. I tried using 2 pair of cheapo cardboard anaglyph glasses, and 1 pair of high quality ones. One of the cheapos gave fair results, one so-so, and the worst results came with the best glasses. Instructions in the 3D view misidentify command-option-S as the key combo to save the 3D view.

So user friendly. I love the 3-D option and make spectacular surreal images.