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At some point I also thought that the orbit trap based ambient occlusion didn't work for the Mandelbox but I was actually mistaken.

The thing I overlooked was the *size* of the Mandelbox - because of this the max and min settings for the orbit traps both need to be increased.

In my formula for UF you can get the correct values for the min and max occlusion values as follows:

1. Switch colouring to "Lighting+Colour".
2. Set the colour to be used to white.
3. Set the lighting method to "Camera".
4. Set the light strength to 1.0.
5. Set the diffuse and specular strengths to 0.0
6. Make sure ambient occlusion is enabled and set the base ambient to 1.0 (leave sourced ambient at zero).
7. Now adjust the min and max values for the orbit trap occlusion - for most Mandelboxes this means increase the values from the defaults.

If anyone has trouble getting it set correctly reply here and I'll post an example UPR tonight (am at work now).

It is possible to do screen-space ambient occlusion in UF, the only problem is that it requires a z-buffer and that's problematic in UF, the rendering would have to be done in the global section with a pseudo-screen buffer as well as the z-buffer (unless the calculations where performed twice), this would be OK for resolutions up to say around 3000 pixels square but until everyone has 64-bit systems and UF is fully 64-bit enabled we'd not be able to render print quality sizes (though it'd be fine for most animations).

I use ssao in to add some depth cues in my realtime viewer and it gives nice results if you dont overuse it (try turning on/off postfx to see difference). Orbit traps probably gives better results though but only works with outside views (although I guess the inverse could work from inside, haven't tried).

I'm working on my own mandelbulb rendering (yay!), can you tell me more (with simple words) about your SSAO please ?
My last try is an (interesting) big FAIL!

After inverting it looks much more better.
However I will try to explain how my SSAO algorithm works.

On the first attached image there is cross-section of the fractal and example rays for one scanning direction. Red line is the z-buffer. On the second image there is view from front (from camera) and scanning directions.

For each scanning direction the algorithm finds minimum angle between camera vector and vectors created by actually calculated point (centre) and scanned point. If the angle is lower it means that in this direction there is less light. Program remembers this "light" intensity as proportional to minimum angle. Of course for this operation each screen coordinate has to be transformed to fractal coordinates.
The same operation must be repeated for each scanning direction. Resultant ambient light intensity is a sum of light intensity for all scanning directions.
For faster calculation of SSAO I have used higher scanning resolution near actual centre point and much lower for far distances (like on second image). Optimal maximum scanning distance is half image width. It gives high detail level and realistic result.
If you want to look at implementation in c++ please download Mandelbulber and find source file image.cpp and function ThreadSSAO(void *ptr)
Third image shows how it looks on whole Mandelbulb. There was used only SSAO for shading.

If something is not clear please ask.

Boxplorer's fake ambient occlusion is computed from distance estimation samples taken along the normal (doesn't need a z-buffer, only 5 extra distance computations per pixel):
, where d = {2δ,3δ,5δ,9δ,17δ}.
Parameter α controls strength and δ controls the scale of details that will be affected by AO.
The technique is explained in http://www.iquilezles.org/www/material/nvscene2008/rwwtt.pdf, pages 47–54.