About raytracing

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Offline Voulxe

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« on: May 04, 2020, 08:00:11 PM »
While digging again into Mandelbulber, I have a few remarks concerning a few topics.
This one is about raytracing.

Depth of field
The photographer in me shivers ... how great it would be to have a line not just a point of focus. Having distance a and b ... anything from camera to a point with distance a is calculated, the range from a to b is ignored, and anything beyond b is calculated again. (That is indeed one of the the three things that I am missing from MB3D)
To overdo this idea ... I imagine to place a sphere in a scene and give it the attribute 'focal area'. That sphere is not rendered but defines an area of focus. ;)

Environment Mapping
I do not understand this option :) With an image loaded, even setting Reflectance to values beyond 10, the render shows no effect.
But I think, this could be a place to load in an HDRI? If not, maybe this could be implemented. ;)

Monte Carlo algorithm
If you have some very much spare time ... An option like the DE-Optimization would be nice. An algorithm that scans a scene for max noise. The result shouldn't be a set of values, but small rendered tile with the given Max Noise level/Max numbers of samples. This way those values can be observed and adjusted without rendering in full resolution.

Thanks again for your time,
Voulxe


Linkback: https://fractalforums.org/mandelbulber/14/about-raytracing/3466/

Offline mclarekin

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« Reply #1 on: May 06, 2020, 01:09:56 AM »
Thanks for your posts, they have not gone unoticed :)
These things i don't deal with  and I think buddhi is on vacation,  so he will respond sometime
However I have been previouslly thinking about the two point DOF.

Offline buddhi

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« Reply #2 on: May 11, 2020, 06:16:55 PM »
DOF:
In real photography there is point of focus (not line). Exactly it is plane of focus located at certain distance from lenses. But it is just certain distance. Until blur radius is lower than pixel size it looks like perfect focus.
Example


I know about option for range of focus in MB3D. But MB3D uses much simpler and less accurate DOF algorithm. Mandelbulber uses double pass DOF (regular blur and reverse blur) and it would be extremely difficult to modify this algorithm tu use range of focus (which is artificial thing as I mentioned).

Environment mapping:
It works only when OpenCL is disabled (not implemented yet for OpenCL rendering engine). It simulates fake reflections based on environment texture.
About environment mapping
https://web.cs.wpi.edu/~matt/courses/cs563/talks/texture/texture/env.html
It has nothing to HDR. If you want to illuminate scene by background texture, just enable MC Global Illumination and use some nice texture for background. You can increase brightness of background texture.



Offline Voulxe

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« Reply #3 on: May 12, 2020, 06:03:51 PM »
Quote
... and it would be extremely difficult to modify this algorithm tu use range of focus ...
Sad news for the freedom of art  :'( 
Quote
If you want to illuminate scene by background texture, just enable MC Global Illumination and use some nice texture for background. You can increase brightness of background texture.
I'll dig into that for sure :)

Thanks for the in depth explanations,
Volker

Offline lycium

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« Reply #4 on: May 12, 2020, 08:27:38 PM »
@buddhi: Actually HDR has a lot to do with environment maps, since the late 90s :) See http://www.pauldebevec.com/Probes/