
Path Tracing 3D Fractals - arunc
http://blog.hvidtfeldts.net/index.php/2015/01/path-tracing-3d-fractals/
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STRML
Those results are fantastic. I have to say, I like the noise that path tracing
creates (you can see it in the video for the Brigade engine as well, mentioned
in another comment). It looks rather like the noise you get from a lower-end
digital camera, which actually rather enhances the realism for me.

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542458
> lower-end digital camera

And here I was going to say "the grain you get from high ISO film
([http://i.imgur.com/4FDyk.jpg)"](http://i.imgur.com/4FDyk.jpg\)"). Dang kids,
get off my lawn!

Anyways, you can actually see this effect (combined with chromatic aberration,
which simulated the effect of cheap camera optics) used to great effect in
P.T., which was a sort of tech demo/playable trailer for an upcoming silent
hill game. Here's a screenshot:
[http://www.silenthillmemories.net/silent_hills/screens/pics/...](http://www.silenthillmemories.net/silent_hills/screens/pics/silent_hills_pt_screen_20140821_02.jpg)

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STRML
Ha, of course, film as well; for whatever reason, my first thought was "crappy
flip-phone camera".

In any case, it's great. The noise hides some details that would otherwise
reveal flaws in the render, similar to how motion blur and focus help as well.

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michiganLepo
Maybe I'm wrong but these fractals are made with raymarching not raytracing
see ex:
[http://www.iquilezles.org/www/articles/mandelbulb/mandelbulb...](http://www.iquilezles.org/www/articles/mandelbulb/mandelbulb.htm)

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rndn
The terminology is admittedly confusing. This is how I understand it:

    
    
       Ray casting:   Determine intersection of a ray analytically
       Ray marching:  Determine intersection of a ray by taking stepwise samples
       Ray tracing:   Ray casting or marching along a light path (from the camera)
       Path tracing:  Ray tracing with random experiments
    

The first two are ray calculation strategies, the latter are rendering
strategies. In ray tracing you usually have many simplifications and effects
like in real-time rendering, for example direct light models. In path tracing
these effects are the result from approximating the full rendering equation.

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Dave_Rosenthal
Hmm, I think some of those definitions are a bit off. Let me try:

\- Ray-casting is the general technique of using ray/object intersections
(usually to solve a graphics problem). Could be via analytical solutions or
not.

\- Ray-marching refers to using an iterative technique for computing
ray/object intersections. This type of strategy is used for these 3D fractals.

\- Ray-tracing creates an image by casting rays for each pixel in the image
(from the camera).

\- Path-tracing is one of many random ray-tracing techniques. It averages
across many random deep bounces of rays following light paths to accurately
solve for lighting.

In this case, the ray-tracing casts rays against the 3D fractal via ray-
marching and uses path-tracing to compute accurate lighting.

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rndn
So path tracing is only used for the secondary rays and beyond?

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Dave_Rosenthal
I think think that's kind of a philosophical question. Wikipedia, for example,
explains path tracing as integrating over incident light on a surface. You
could either think of that as incident light at a point on a virtual
film/sensor plane behind a lens or incident light on the first object you hit
in the scene.

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ska
Such techniques are often generally known as "Global Illumination".

Often in physics based rendering you are attempting to estimate the BSDF (bi-
directional scattering distribution function, often broken into T,
transmission and R reflection) parts. This gets complicated by interactive
media and subsurface scattering (i.e the photons go into a material and bounce
around) but in the simple case of a surface interaction you are estimating an
integral over solid angle for all light interactions. Monte Carlo path tracing
is one way to do this estimation.

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higherpurpose
What gaming engines already implement or plan to implement path tracing in
them in the future? Path tracing looks like the future of gaming graphics, and
would do especially well with VR in a decade or so (hopefully by then path
tracing will also be accelerated in hardware).

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tpaksoy
There is the Brigade engine[1] that I know of. It's as far as I know a one man
project. I haven't heard of an update in a long time though.

[1]
[https://www.youtube.com/watch?v=BpT6MkCeP7Y](https://www.youtube.com/watch?v=BpT6MkCeP7Y)

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Gravityloss
[http://raytracey.blogspot.fi/](http://raytracey.blogspot.fi/)

Sam Lapere seems to have left Otoy around November 2014.

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berkut
I'd guess Jacco Bikker and Jeroen van Schijndel are still involved though?

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joshu
I've been following this blog for a bit. Fragmentarium is pretty interesting.

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maulik13
The results look great!

