'Fish eye'

[domejunky]

Hello All,

Loving the software! I am interested in rendering for Fulldome (Planetarium). I got particularly excited about the 'fish eye' option - I have been playing with it for a couple of days, and looking at the source, trying to work out what projection it actually is. It is referred to as a 'spherical', which I think is what I would call 'equirectangular' - I have tried various combinations of FOV and image size, trying to create a 2:1 aspect equirectangular - since these can be correctly manipulated to derive the fisheye projection we need for our dome.

Any pointers gratefully received...


Pete

[FractalFoundation]

Hi Pete - glad you're enjoying Mandelbulber! It's an amazing program, for sure. I've rendered several pieces for our planetarium fractal shows, some of which you can check out here: http://vimeo.com/fractalfound/videos
In general I don't use the 'fisheye' option, but just adjust the Filed of View (FOV) to a value that I determine looks best, which depends on the particular fractal type. Using a cube shape, like a mandelbox or menger sponge is a good reference to check in the dome, but individual fractals will look best with different FOV values, so I encourage you to play with that. I didn't like the effect of the native fisheye option, but I'd love to see any results you come up with if you manage to adjust the source code to render better on a dome. I will say, it's much harder to navigate in fisheye mode, and you have to generate your flight paths in fisheye, as it won't work to create an animation and then switch over to fisheye.
Anyway, best of luck, and I'd love to see what you come up with.

-Jonathan

[domejunky]

Johnathan,

I believe I have seen some of your fractals in Albuquerque - I still tell people the 'scalping tickets at fractal fridays' story that Beining told....

I can't work out the projection - not equirectangular, nor cylindrical from what I can make out - These are conversions to 'fisheye' projection assuming first equi, then cylindrical mappings:






But it's tantalising.

I've been trying to hack the source, since it's a Raytracer I thought I could compare formulas with Yafaray, which has a working fisheye camera. I'm not really familiar with the Mandelbulber source, so I'm working blind really. I keep looking for "if (sphericalPersp)" in Render3D.cpp - but it's hard to know how much of the code is due to the fact that we're rendering fractals - something I have no experience with.

Pete

 

[Buddhi]

Loving the software! I am interested in rendering for Fulldome (Planetarium). I got particularly excited about the 'fish eye' option - I have been playing with it for a couple of days, and looking at the source, trying to work out what projection it actually is. It is referred to as a 'spherical', which I think is what I would call 'equirectangular' - I have tried various combinations of FOV and image size, trying to create a 2:1 aspect equirectangular - since these can be correctly manipulated to derive the fisheye projection we need for our dome.

Hi

I would like to help you in this topic. I'm not sure what type of projection I have implemented (it not fit to any formal definition). My target was to do "fish eye" effect. Please define projection what you need using formulas, then I will try to implement it in Mandelbulber.

Now if you set 'fish eye' mode, FOV to 1.0 and image aspect 2:1, you have 360 degree horizontal view and 180 degree vertical, like on picture above:

 

[domejunky]

Hello,

Selfishly, I would like to render to a 180 degree circular fisheye projection, but could use equirectangular (spherical) just as easily...Content for domes often needs to be rendered to match the tilt of the dome screen, so without that control, equirectangular might be preferable to enable re-tilting in post...

Probably the most succinct source on the topic is Paul Bourke:

http://local.wasp.uwa.edu.au/~pbourke/miscellaneous/lenscorrection/

Pete

[olihar]

I wonder and am really interested in the spherical view.

I ran a test on how the left and right side would join up together in a spherical viewer...



Wonder what could be done to get it seamless...

[Buddhi]

I wonder and am really interested in the spherical view.

I ran a test on how the left and right side would join up together in a spherical viewer...

Wonder what could be done to get it seamless...

I think that your image is not seamless because:
- you used Screen Space Ambient Occlusion, which depends on image data. Near image borders this effect is less accurate. You should use Shaders/Shading effects/Ambient occlusion and switch off Post effects/Screen Space Ambient Occlusion.
- background should be a solid color or as a textured background (also seamless)

[Buddhi]

Selfishly, I would like to render to a 180 degree circular fisheye projection, but could use equirectangular (spherical) just as easily...Content for domes often needs to be rendered to match the tilt of the dome screen, so without that control, equirectangular might be preferable to enable re-tilting in post...

I have made some changes in spherical transform formula. Now it should work when you wrap this image into sphere. Please test this image.

[domejunky]

Spot on! That works like a charm....




Are the modifications in the subversion repository?


Pete

[Buddhi]

Are the modifications in the subversion repository?

Not yet. I will do it tomorrow.

[domejunky]

That's an infinite amount of time to wait in the world of fractals,  any chance of posting the modifications you made...? I'm assuming they were modifications to Render3D.cpp...


Pete

 

[Buddhi]

That's an infinite amount of time to wait in the world of fractals,  any chance of posting the modifications you made...? I'm assuming they were modifications to Render3D.cpp...

I will short your waiting. I have just uploaded changes into subversion repository. This spherical projection is temporary replacing 'fish eye' option. If you want to see changes please go to: http://code.google.com/p/mandelbulber/source/diff?spec=svn94&r=94&format=side&path=/trunk/src/Render3D.cpp&old_path=/trunk/src/Render3D.cpp&old=93

[domejunky]

Thanks for that Buddhi,

I may be gone some time....


Pete

[olihar]

Here yes, this seems to work like a charm now...

I tested your image..
http://olihar.com/fractal/

[Buddhi]

I will add this option permanently to the Mandelbulber, because it is very interesting possibility to show fractals.

New example (using panorama viewer):
http://www.dermandar.com/p/cyFCvT/mandelbox

Thank you domejunky for inspiration